35:T6013,

Dr. Vicki Ellen Szabo, Western Carolina University

Entangled right whale, 2010, NOAA News Archive 123110, fish2378, NOAA's Fisheries Collection.

2017 was a calamitous year for the North Atlantic right whale. The final count of the 2017 "Unusual Mortality Event" or UME, as defined by the Marine Mammal Protection Act, was eighteen animals. Fourteen North Atlantic right whales were found dead from the Gulf of Saint Lawrence to Cape Cod between June and December, with an additional four strandings and entanglements through the year. An average annual mortality rate for the North Atlantic right whale is four animals. To make matters worse, these right whales began 2017 with an estimated population of just 450 animals, including only about one hundred breeding females who have exhibited such stress in recent years that their breeding rate has slowed. As proof of this, in addition to the UME, 2017 saw no recorded calf births.

The cause of the UME is no mystery; warming waters have expanded the whales' habitat further north. Bypassing their usual feeding grounds in the Gulf of Maine, most of the whales were found entangled or dead in the Gulf of St. Lawrence, where they have sought out their favorite food, Calanus finmarchicus or copepods, a cold water species. Measures in place in more southern waters to prevent entanglements and ship strikes haven't been implemented further north, but as the whales move, so too must these regulations – if there is time left. Marine ecologist Mark Baumgartner of Woods Hole Oceanographic Institution ominously noted in December 2017 that North Atlantic right whales, without immediate intervention and protective measures, would be extinct in twenty years. The story of the North Atlantic right whale may end in 2040, but the beginning of the end of this species may have begun a thousand years earlier.

2017-2018 North Atlantic Right Whale Unusual Mortality Event, from NOAA Fisheries Marine Life in Distress.

North Atlantic right whales, Eubalaena glacialis, earned their common name because of the ease with which they were hunted – they were literally the 'right' whales to hunt. Right whales are bountiful in blubber, giving them exceptional buoyancy, even after death. Their shallow coastal habitat, slow swimming speed, docility, and sizeable pods - averaging twenty but recorded in superpods of one hundred animals - made them accessible and attractive to coastal predation. Averaging fifteen meters in length and 40 - 100 tons in weight, a single right whale could feed and supply a premodern community for months.

The deck is stacked, it would seem, against the Atlantic species, and it is clear that all of these natural factors led to significant premodern exploitation of the right whale across the Atlantic. While a population of right whales also exists in the Pacific, predation or natural causes have not led to a dramatic population decline as we see in the Atlantic. Biologists have estimated around 5500 right whales taken across the North Atlantic from the 17th through the early 20th centuries. Reaching an estimated population low of 100 in the 1930s, the species’ brief recovery to approximately 500 animals in the modern era is cold comfort. Without a sense of a historical baseline or 'natural' population of North Atlantic right whales, both in population size and genetic diversity, it is difficult to estimate what a recovered population should look like and whether recovery is even possible.

Historians and marine biologists recognize that human exploitation and interference have had a massive impact on the North Atlantic right whale, particularly during and since the sixteenth century. Randall Reeves says that this species has suffered from “one of the most extensive, prolonged, and thorough campaigns of wildlife exploitation in all of human history.” It is a challenge, though, to determine the full extent of human interference in the case of premodern depletions of extinctions. North Atlantic right whales once existed in two presumed separate breeding populations. Still extant, for now, is the population local to the western North Atlantic and the North American coastline. An eastern North Atlantic population, thought to have bred off the coast of the Canaries and migrated along the Atlantic coast to the Subarctic, is presumed extinct. Of this population, though, we know almost nothing with respect to population size, species duration, or genetic diversity. Did changes in premodern climate – the Medieval Climatic Anomaly and the Little Ice Age – affect the whales' migrations and habitats alongside human interference? Were right whales so heavily predated in premodernity that non-industrial whaling could bring about the end of a population? This is the case typically made for North Atlantic gray whales, extinct by the eighteenth century, and for the eastern population of North Atlantic right whales. Does this also explain the precarious state of the western population of North Atlantic right whales?

Reeves, in 2007, wrote that “historical research has provided a general perspective on past right whale distribution, population structure, and numbers, but understanding of just how abundant these animals were when whaling began in the North Atlantic remains vague." In 2008, Brenna McLeod led a genetic analysis of historical North Atlantic right whale remains from whaling stations up and down the Labrador coast. McLeod and her team concluded that “the pre-exploitation population size of right whales was clearly much smaller than previously estimated [which] has effected our modern impressions of the recovery of right whale stocks.” In short, predation almost certainly played a role in the species' decline, but the degree remains unclear.

The deep history of North Atlantic right whales and their ill-fated engagements with human populations could offer a valuable lens at this critical moment for the species. Historical and archaeological proxy data on cetacean populations, especially for the North Atlantic right whale, may contribute to analysis of modern species populations, habitats, behaviors, and other statistics. Working back from peak points of exploitation through the earliest records of right whale use, historical and archaeological evidence may provide useful context for this imperiled species.

Basque Whale-Fishing. Facsimile of a Woodcut in the "Cosmographie Universelle" of Thevet, in folio: Paris, 1574. Project Gutenberg text 10940.

We often begin the story of the North Atlantic right whale extirpation with the medieval Basques, who historically have been blamed for the destruction of the eastern branch of the North Atlantic right whale. The Basques established some of the earliest whale fisheries along the European Atlantic coast, maintaining those fisheries from the 13th through the early 20th centuries. Forty-seven medieval and early modern French and Spanish Basque ports have been identified as possible whale fisheries. Alex Aguilar, using catch data from its beginnings in the 16th century, estimates that each port may have taken one or at most two whales a year through the eighteenth century.

Far from the depredations wrought by industrial whaling, even this small catch was enough to make an impact on the population, as the Basques were known to target whale calves, and the Bay of Biscay may have been the winter nursery for the eastern population of the North Atlantic right whales. In some ports, Aguilar concluded that the catch of calves accounted for over 20% of records. Additionally, mothers will follow struck calves, making them more readily subject to predation as well, and removing breeding females from the population. This hunting strategy, common among preindustrial whalers, would explain the apparent downturn in catch records by the 18th century and a thinning population that may have precipitated Basque movements to new hunting grounds in North America and the Northeastern Atlantic and Subarctic, where their quarry was the western population of North Atlantic right whales. Also to be considered are possible changing habitats and migrations over the course of the Little Ice Age, when Bowhead whales may have moved south into the Subarctic, potentially competing with right whales for prey.

Basque whalers in Labrador reportedly caught well over 20,000 animals, presumed, again, to be right whales. Archaeological and historical investigations of around twenty whaling ports along the Labrador shore, focusing especially on the major Basque port of Red Bay, have forced a reassessment of the role of the Basques in right whale extirpation. In genetic analysis of nearly three hundred whale bones from ten of those ports, only one sample was identified as right whale. Over two hundred bones came from bowhead whales, of which 72 individual animals were identified. The unanticipated number of bowheads on these sites has altered our perceptions not only of the right whale's decline, but also of the expected habitats of the bowhead. While not clearing the Basques of impact in the decline of the right whales, their involvement may not have been central to this population’s decline. The Basques had another crack, potentially, at the North Atlantic right whales during their ill-fated residence in the Icelandic Westfjords, but they weren’t the only hunters targeting these animal populations.

Sléttbakur (right whale); Handrit Jóns Guðmundssonar lærð, JS 401 XI a 4to, National and University Library of Iceland.

Right whales and their utility to human societies has been documented for over a thousand years in Europe. This documentation largely comes from the Northern world, and specifically from Norse populations, from the homeland and across the diaspora. Norse whalers in Ireland, according to a Spanish geographer, spent the 11th century picking off right whale calves, perhaps from the same population travelling through the Bay of Biscay: "… on their coasts, [the Norsemen] hunt the young of the whale, which is an exceeding great fish. They hunt its calves, regarding them as a delicacy. They have mentioned that these calves are born in the month of September, and are hunted in the four months October to January. After this their flesh is hard and no longer good for eating…. Then they cut up the meat of the calf and salt it. Its meat is white like snow, and its skin black as ink." The North Atlantic right whale migration up the European coast peaked in January, but lasted from October through March, according to Aguilar's analysis of the Basque hunt in Spain and southern France. If right whale calves were being taken at multiple points up and down the European coast, the seemingly minimal catch of the Basque ports become magnified in its impact.

In addition to the Norse whalers of Ireland, Norsemen back in the homeland itself had already been targeting right whales some three centuries prior. The laconic merchant-hunter Ottar was an Arctic hunter of right whales off the coast of northern Norway, or so he told King Alfred and his court in the ninth century. The whales of Ottar's homeland, he noted, were far bigger than those he fished from the sea off Tromsø, but his ship, along with five others, reportedly killed sixty large whales in the span of two days. Ottar describes the whales as being up to 20 meters long, and while perhaps exaggerated, many historians have surmised that his quarry were right whales, a species called "the first commercial whale." For ninth-century Norsemen, the ability to shoot at and kill whales was second, perhaps, to their capacity to control and acquire. A whale that sank was of no good to anyone, but whales that floated would certainly be keenly sought. Barring any reference to netting, floats, or lines secured by harpoons, a primitive hunter could kill and acquire a right whale if conditions were right.

There is good reason to place faith in the ability of hunters like Ottar or the Hiberno-Norsemen to recognize whales they could catch. The twelfth-century anonymous King's Mirror, old Norse Konungs skuggsjá , described the behavior and appearance of over a dozen species of North Atlantic whales. Medieval manuscript illuminations from Scandinavian and Western European texts depict whales in various recognized activities that awe and delight us today - breaching, porpoising, spy-hopping, logging and especially predation. Among the most articulate and observant of all premodern authors was the late medieval Icelander Jón Guðmundsson, also known as Jón Laerði, or Jon the Learned (1574-1658). Jón was a sorcerer and a poet, a physician, outlaw, artist, fisherman, historian, and naturalist. He possessed a wealth of local, traditional environmental knowledge on seafaring, fishing, and especially on whales.

Jón Laerði, or Jon the Learned (1574-1658), illustration of whale species from his Natural History of Iceland, GKS 1639 kvart, Royal Library, Copenhagen; photo courtesy of Icelandic Museum of Natural History.

Jón was born and lived in the Snaefellsness peninsula in Western Iceland, where he says he saw many whales. He also lived in the Westfjords, where he witnessed and recorded the infamous killing of Basque whalers in 1615. Sometime before his death, perhaps around 1640, Jón wrote a work called the Natural History of Iceland in which he illustrates and describes twenty-two whale species of Iceland. According to Viðar Hreinsson, recent biographer of Jon Laerði, Jón compiled illustrations with Danish captions of nineteen whale species, in addition to a rather skinny walrus, on a loose leaf of paper preserved in the Royal Archive in Copenhagen. The right whale according to Jón exists in two varieties, one smaller, the sléttbakur and a larger animal which he calls höddunefur, measuring 35 ells at the longest (about 17 meters). The smaller whales are the ones most hunted, particularly for their valuable blubber. Icelandic waters, he notes, had been home to a large number of those whales, but the "foreign whalers have reduced the number of this species the most." One wonders which of the right whales – western or eastern North Atlantic - were being preyed upon and whether the diminished species, which he notes, was the beginning of the end of the North Atlantic right whale.

In what ways can past histories tell us something new, critical or important about modern animal populations? In the case of the North Atlantic right whale, new technologies like ancient DNA analysis offer a possible means of insight into the current state of this population and context for the references to the species throughout medieval and early modern literature and history. Through an ongoing National Science Foundation Arctic Social Science project, (NSF # 1503714, Assessing the Distribution and Variability of Marine Mammals through Archaeology, Ancient DNA, and History in the North Atlantic; henceforth Norse North Atlantic Marine Mammal Project or NNAMMP) genetic materials from whale remains found on numerous archaeological sites in the North Atlantic and Subarctic may provide evidence related to modern right whale populations.

Archaeological sites across the North Atlantic often preserve fragments of marine mammal bones both as artifacts and as butchery or bone working residue. The Norse North Atlantic Marine Mammal Project has compiled over 200 worked and waste whale bone samples from a dozen archaeological sites in Iceland, Greenland, North America, the Faroes and Orkney, ranging from 800 through 1500 CE. Whale bone is a challenging resource for archaeological analysis, defying typical zooarchaeological standards for data recording and analysis. Whale bone is not transported to archaeological sites as part of animal butchery, so bones that are found on a site do not follow regular butchery patterns. Depending on the size of the animal stranded, only 10 to 15% or less of an animal’s body weight may be derived from hard tissues; in the case of North Atlantic right whales, about 13% of an animal’s body weight is bone. This detail becomes important when you consider that the physical evidence of premodern whale use must come from this small percentage of hard tissues, of which only a fraction – if any at all – is transported from a coastal butchering site to an inland settlement.

Complicating matters, medieval laws and charters, in Iceland and across the Continent, scrupulously divide stranded whales based on location of stranding, species, class or status of the claimant, and other factors. With all of these metrics in play, recovery of whale bone is not assured on any site, and the bone present on a site may not attest to the quantity of soft tissues used from any animal. Further, to isolate the bones of a single species from massively modified and fragmented whale bone creates an additional challenge for species analysis.

Archaeological site at Siglunes, Eyjafjörður; note large fragment of whale cranium in the left foreground. Photo reproduced with permission of Dr. Ramona Harrison, University of Bergen, and Fornleifastofnun Íslands (FSI).

Despite these challenges, the Norse North Atlantic Marine Mammal Project and Brenna McLeod at the Frasier lab at St. Mary's University have identified over thirteen unique cetacean species within 200+ bone samples. In those samples, nine unique examples of Eubalaena glacialis have been genetically confirmed across the sampled site assemblages. Over the course of the next year, our project will continue to identify and analyze additional bone samples from across the North Atlantic. Microsatellite analysis of nuclear DNA from identified samples will help to refine which populations of North Atlantic right whales have been found across archaeological sites from North America, Iceland, Greenland, and the Orkney Islands. By 2020, our project will have analyzed over 400 whale bones and we hope to tell a number of species stories, not postscripts, on the whales of the North Atlantic.

Selected Works Cited:

Active and Closed Unusual Mortality Events. NOAA Fisheries. https://www.fisheries.noaa.gov/national/marine-life-distress/marine-mammal-unusual-mortality-events

Aguilar, Alex. “A Review of Old Basque Whaling and its Effect on the Right Whales (Eubalaena glacialis) of the North Atlantic.” Report of the International Whaling Commission, Special Issue 10 (1986): 191-199.

Dunlop, D. M. “The British Isles according to Medieval Arabic Authors.” Islamic Quarterly 4 (1957): 11-28.
Hreinsson, Viðar. Jón lærði og náttúrur náttúrunnar (Jon the Learned and the Nature of Nature). Reykjavik: Lesstofan Press, 2016.

Laist, David W. North Atlantic Right Whales: From Hunted Leviathan to Conservation Icon. Baltimore: Johns Hopkins University Press, 2017.

Lindquist, Ole. Peasant Fisherman Whaling in the Northeast Atlantic Area, CA 900-1900 AD. Akureyri: Háskólinn á Akureyri, 1997.

Lindquist, Ole. “Whaling by Peasant Fishermen in Norway, Orkney, Shetland, the Faeroe Islands, Iceland and Norse Greenland: Medieval and Early Modern Whaling Methods and Inshore Legal Régimes.” In Whaling and History Perspectives on the Evolution of the Industry. Eds. Bjørn L. Basberg, Jan Erik Ringstad, and Einar Wexelsen. Sandefjord: Kommandor Chr. Christensens, 1995, 17-54.

McLeod., B., M. Brown, M. Moore, W. Stevens, S. H. Barkham, M. Barkham and B. White. “Bowhead whales, and not right whales, were the primary target of 16th to 17th-century Basque whalers in the Western North Atlantic.” Arctic 61.1 (2008): 61-75.

McLeod, B. et al., “DNA profile of a sixteenth century western North Atlantic right whale (Eubalaena glacialis).” Conservation Genetics (30 Jan. 2009). 10.1007/s10592-009-9811-6.

“North Atlantic right whales on the brink of extinction, officials say,” The Guardian, 10 Dec. 2017.
https://www.theguardian.com/environment/2017/dec/11/north-atlantic-right-whales-brink-of-extinction-officials-say

Palumbi, Stephen R., "Whales, Logbooks, and DNA.” In Shifting Baselines: The Past and the Future of Ocean Fisheries, ed. by Jeremy B. C. Jackson, Karen E. Alexander, and Enric Sala, 163-173. Washington DC: Island Press, 2011.

Proulx, J. ‘Basque Whaling Methods, Technology and Organization in the 16th Century.” Trans. A. McGain. In The Underwater Archaeology of Red Bay: Basque Shipbuilding and Whaling in the 16th Century, Volume 1, ed. R. Grenier, M. Bernier and W. Stevens, 42-96. Ottawa: Parks Canada, 2007.

Rastogi, T., M.W. Brown, B. A. McLeod, T. R. Frasier, R. Grenier, S. L. Cumbaa, J. Nadarajah and B. N. White 2004. “Genetic analysis of 16th-century whale bones prompts a revision of the impact of Basque whaling on right and bowhead whales in the western North Atlantic.” Canadian Journal of Zoology 82 (2004): 1647-1654.

Reeves, R. R., T. Smith and E. Josephson. “Near-annihilation of a species: Right whaling in the North Atlantic.” In S.D.Kraus and R. M. Roland (eds), 39-74. The Urban Whale: North Atlantic right whales at the crossroads. Cambridge MA: Harvard University Press, 2007.

Roman, Joe and Stephen R. Palumbi. “Whales Before Whaling in the North Atlantic.” Science 301 (25 July 2003): 508-510.

Soviet Illegal Whaling in the North Pacific: Reconstructing the True Catches. NOAA Fisheries, 2012. https://www.afsc.noaa.gov/quarterly/ond2012/divrptsNMML2.htm

Szabo, Vicki. Monstrous Fishes and the Mead-Dark Sea: Whaling in the Medieval North Atlantic. Leiden: Brill, 2008.

Teixeria, R. Venancio, and C. Brito. "Archaeological remains accouting for the presence and exploitation of the North Atlantic right whale Eubalaena glacilis on the Portuguese coast (Peniche, West Iberia), 16th to 17th century." PLOS One 2014 9(2): e 85971 / doi 10.1371/journal.pone.0085971

36:T4847,

Dr. Dagomar Degroot, Georgetown University

Aert van der Neer, “Riviergezicht bij Winter,” c. 1655-1660. Rijksmuseum Amsterdam

Earth’s climate is changing with terrifying speed. Humanity has added several hundred billion tons of carbon dioxide to the atmosphere, strengthening a greenhouse effect that has now warmed the planet by roughly one degree Celsius. The scale, speed, and causes of today’s global warming have no precedent, but of course natural forces have always changed Earth’s climate. We now know that these changes were big enough to shape the fates of past societies. Most confronted disaster, but a few seemed to prosper in spite of – and in some cases because of – climate changes. Perhaps the most successful of all emerged in the coastal fringes of the present-day Netherlands. It has left us with lessons that may offer new perspectives on our fate in a warmer world.

To contextualize present-day warming, paleoclimatologists have scoured the globe for signs of past climate change. They have found layers buried deep in glacial ice and cave stalagmites, sediments embedded in lakebeds and ocean floors, and rings wound around tree trunks and stony corals. All bear silent testament to ancient weather. Together, they reveal that, sometime in the thirteenth century, Earth’s climate started cooling.

Huge volcanic eruptions lofted dust high into the stratosphere that blocked incoming sunlight. The Sun itself slipped into a dormant phase, sending less energy to the Earth. A long-running shift in Earth’s axial tilt gradually reduced the amount of solar energy that reached the northern hemisphere. Sea ice expanded, wind patterns changed, and ocean currents altered their flow. Patterns of precipitation fluctuated dramatically, bringing torrential rains to some places, and unprecedented droughts to others. A long “Little Ice Age” had begun.

A tree ring reconstruction of average summer temperatures in the Northern Hemisphere over the past 2,500 years (red), with a thirty-year moving average (blue). The baseline (“0”) is the late twentieth-century average. Temperatures in the seventeenth century were cold but erratic. Developed from M. Sigl et al., “Timing and Climate Forcing of Volcanic Eruptions for the Past 2,500 Years,” Nature 523 (2015): 545.

In the closing decades of the sixteenth century, this Little Ice Age reached its chilliest point across much of the northern hemisphere. By then, the world had cooled by nearly one degree Celsius, relative to average temperatures in the twentieth century. In many places, weather had also grown more volatile and less predictable from year to year, season to season. Despite its name, the Little Ice Age involved more than constant cooling.

Historians, historical geographers, and archaeologists have argued that the onset of the coldest and most erratic phase of the Little Ice Age could not have come at a worse time. For centuries, populations in the greatest empires of the day had steadily increased. By the sixteenth century, millions depended on crops stubbornly cultivated in arid, unproductive farmland. When falling temperatures shortened growing seasons, when monsoons failed, or when storms flooded fields, harvests in these regions failed again and again.

Many farmers responded by swapping crops that prefer warm, stable weather for those that cope better with cold, volatile conditions. Some diversified their fields. Yet often there was just no dealing with droughts, torrential rains, or cold snaps that lasted for longer than a year or two. Famine and then starvation spread from the plains of the Aztec Empire to the woodlands of the Mutapa Kingdom, from the steppes of the Grand Duchy of Moscow to the rice fields of the Ming Dynasty.

The worst was yet to come. Temperature and precipitation extremes sickened plants and animals alike, compounding food shortages. As temperatures dropped, farmers huddled in huts with their ailing livestock. In those conditions, diseases spread easily from animals to people. Malnourished human bodies, meanwhile, have weak immune systems, which makes them easy prey for bacteria and viruses. Changing weather patterns also altered the range of insects that carried disease pathogens, bringing new and deadly ailments to the previously unexposed. In empire after empire, millions fled from the famine-stricken countryside, unwittingly infected by diseases that they carried to cities. Where famine lingered, epidemic outbreaks often followed.

In one empire after another, the sick and starving blamed governments for their misery. They were usually right. Few governments responded constructively to the crises they faced, and most made them worse by, for example, increasing taxes or embarking on wars. The coldest stretch of the Little Ice Age therefore coincided with an unprecedented surge of revolts and civil wars. Rebel and state armies alike conscripted farm laborers from the already overburdened countryside, imposed new demands on marginal farmland, and joined refugees in spreading disease. In the end, millions died.

Yet remarkably, inhabitants of the Dutch Republic – the precursor state to today’s Netherlands – enjoyed a Golden Age that perfectly coincided with the chilliest century of the Little Ice Age. Somehow, a country with about as many people as Providence, Rhode Island emerged as a European great power, with a navy that went from victory to victory, an army that held the mighty Spanish Empire at bay, and a commercial fleet that dwarfed all others. Today, the art of Rembrandt and Vermeer – painted in the coldest years of the Little Ice Age – gives a distant echo of the energy and prosperity of those incredible times.

The Dutch Republic was something of an oddball in the seventeenth-century world. The overwhelming majority in most societies toiled in rural fields, growing crops for local markets. Many Dutch farmers, by contrast, cultivated cash crops for distant consumers. The republic therefore depended on a steady flow of grain imports from the rich and diverse farmland along the Baltic Sea. Over time, a growing share of Dutch citizens worked in commercial interests and industries with headquarters in or near port cities that would have been underwater, were it not for an extensive network of dikes and sluices. Urbanization rates were soon higher in the republic than they were just about anywhere else. Meanwhile, tens of thousands of sailors plied Dutch trades that reached deep into the Arctic, the Americas, Africa, and Asia.

Amsterdam just before its rise to global prominence. Cornelis Anthonisz., “Bird's eye view of Amsterdam,” 1538. Amsterdam City Museum.

Sailing depended on two things: favorable winds and open, ice-free water. By changing currents and cooling temperatures in the atmosphere and oceans, the chilliest stretches of the Little Ice Age therefore affected sailing as much as farming. Yet the impact was very different. New wind patterns actually sped up ships that left the republic for Asia or America, shortening their journeys.

In the waters off northern Europe, storms were unusually frequent and severe in the coldest stretches of the Little Ice Age. Many ships foundered, and many sailors drowned. Yet crews aboard the republic’s biggest merchant ships – ones that carried the richest cargo from distant markets – weathered storms much better than sailors aboard other European ships. In fact, storms often benefitted Dutch sailors by further increasing the speed of these big ships.

Even sea ice aided the Dutch, including in the Arctic. It took plenty of sea ice – but not too much – to redirect Dutch voyages of northern exploration towards the rich bowhead whale feeding grounds off the archipelago of Svalbard, which lies between the northern coast of Norway and the North Pole. Whalers from all over Europe soon set up shop there. For a long time, the edge of the Arctic pack ice lingered near Dutch whaling stations, and since whales gathered along the edge of the ice, the Dutch benefited. By following the ice edge west, Dutch whalers even found whale breeding grounds off the little island of Jan Mayen.

The Dutch fought most of their wars on or around water. Climatic cooling may have benefited their armies and fleets even more than their merchants. The Dutch flooded their own farmland to thwart Spanish and later French invasions. Some of these floods would not have succeeded without torrential rains that reflected new atmospheric realities.

Later in the seventeenth century, cooling coincided with a shift in the strength of atmospheric high and low pressure zones over the Atlantic Ocean, which sharply increased the frequency of easterly winds over northern Europe. Sailors aboard Dutch warships heading into battle from the republic often had what was then called the “weather gage:” the upwind position from a downwind opponent. That allowed them to decide exactly how and when to deploy new “line of battle” tactics, in which warships would sail by each other in single file while firing broadsides. New wind patterns played a role in helping the Dutch win wars they might otherwise have lost.

The wind blows from the left to the right in this painting from the First Anglo-Dutch War (1652-54). The Dutch ship in the center therefore has the weather gage, while the English flagship it is fighting does not. Jan Abrahamsz. Beerstraten, “Slag bij Ter Heijde,” 1653-1666. Rijksmuseum Amsterdam.

Still, climate change did not always aid the Dutch. In the Arctic, sea ice crushed ships, drowned sailors, and screened whales from whalers. Sailors in small ships that carried grain and timber from the Baltic Sea endured violent storms and confronted thick sea ice that blocked their way. Cold snaps in the Baltic occasionally led to harvest failures that imperiled the republic’s precious grain imports. Ice repeatedly blocked the waterways of the republic, suffocating travel between cities and raising the specter of flooding when the ice thawed. Sometimes, ice froze rivers that otherwise served as barriers to invasion. Left unattended, candles and stoves in cold winter weather kindled fires that swept through the cities of the republic.

Time and again, the Dutch responded creatively. Shipwrights fortified the hulls of whaling ships and greased them until they slid off ice. Civilians and soldiers hacked through ice to preserve open water in their defensive rivers. Guilds and city governments bought icebreakers that not only kept waterways open, but actually manufactured ice blocks for use in cellars. When the ice was too thick, the Dutch used skates and sleds to turn frozen canals into busy thoroughfares. Merchants divided their goods between different ships, and invested in marine insurance. They stockpiled Baltic grain in good years, and sold it for healthy profits whenever food shortages plagued Europe. Charities maintained a steady supply of food for the urban poor. Inventors pioneered new firefighting tactics and equipment, and made good money selling them across Europe.

Jan van der Heyden’s “Fire Hose Book” depicts the storm-kindled fire of July 27th, 1679. Jan van der Heyden, “Oude brandspuiten en nieuwe slangbrandspuiten in de praktijk,” print, 1690, Rijksmuseum Amsterdam.

The Dutch, in short, were lucky to benefit from environmental changes that favored their unusual economy. But they also made their own luck. The society they built ended up being remarkably resilient in the face of new weather patterns that spelled disaster elsewhere in Europe. By relying so heavily on farmers scratching out a meagre existence on marginal farmland, other civilizations developed vulnerabilities to climate change that simply did not exist in the Dutch Republic.

In fact, the Dutch may even have adapted their technologies and policies to exploit the Little Ice Age, though they may not have recognized the trends in weather that we call climate change. Why were they so flexible in the face of changing environmental circumstances? In part, the answer may lie in their long history of draining and damming the Low Countries. The Dutch long understood that environments can change, and that societies can either adapt or succumb.

There was a darker side to the republic’s prosperity. The Dutch thrived in part by preying on communities and civilizations the world over. They shattered Iberian trading monopolies in Asia, seized expansive territories in the Americas, overwhelmed English whalers in the Arctic, and infamously broke into an African slave trade that cruelly exploited millions of people. The weather extremes of the Little Ice Age had often weakened communities that the Dutch victimized. In the republic, adaptation to climate change could take the form of a parasitic kind of opportunism that leveraged vulnerabilities in other societies.

What, then, can the history of the republic’s frigid Golden Age teach us today? First and perhaps most importantly, it shows us that even relatively small changes in Earth’s average temperature can have enormous social consequences. Across much of the seventeenth-century world, the gloomiest predictions for our warmer future came true. A third of humanity may have died in disasters either set in motion or worsened by climate change.

The world has already warmed more, relative to average temperatures in the twentieth century, than it cooled in the chilliest stretches of the Little Ice Age. Our best projections suggest that it will warm by roughly three degrees Celsius in the coming century, if and only if countries follow through on their Paris Agreement pledges. Histories of the Little Ice Age therefore give us an urgent call to arms. We have technologies that our ancestors could not have imagined. But there are far more of us, consuming unimaginably more plants and animals, metals and fuels. And we too depend on a huge network of fields and fisheries that may not survive drastic changes in temperature and precipitation.

That leads us to our second lesson: climate change has had, and probably will have, very unequal consequences for different societies, communities, and individuals. Many assume that rich societies cope best with climate change. Yet some of the wealthiest seventeenth-century empires actually fared worst in the coldest and most volatile years of the Little Ice Age. Climate change, it seems, imperils not only societies that have few resources to exploit, but also those that require abundant resources to prosper.

The Dutch thrived in the seventeenth century not because their republic was rich, but because much of its wealth derived from activities that climate change benefited. Today, we can learn from the republic by strengthening social safety nets, investing in technologies that exploit or reduce climate change, and more broadly by thinking proactively about how we will adapt to the warmer planet of our future. We can learn from the Dutch in another way too, by strengthening bonds between countries and communities, rather than preying on the most vulnerable.

Ultimately, the lessons of the past come to us in the form of parables: stories that hint at deeper truths but do not tell us exactly what to do. That does not make them any less valuable. We now know that we cannot ignore our changing climate, that it will shape our fortunes in the decades to come. Let us use the warnings of the past to confront the looming catastrophe in our future, while we still can.

This article summarizes some important ideas in my new book, The Frigid Golden Age: Climate Change, the Little Ice Age, and the Dutch Republic, 1560-1720. You can buy the hardcover on the Cambridge University Press website or on Amazon, and you'll soon be able to purchase the paperback.

The Washington Post published a modified and much shorter version of this article. You can find it here.

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Dr. Ruth Morgan, Rachel Carson Center for Environment and Society

Protest in Bonn at the start of COP 23. Photo by Spielvogel.

I joined the most recent UN Climate Change Conference in Bonn with a delegation from Monash University, which also included legal scholars, renewable energy specialists, and science communicators. The opportunity to observe and participate in the activities that accompany the negotiations was too good to pass up. Both personally and professionally, I have closely followed the machinations of international climate politics over the past decade, with particular attention to the work of Australian scientists and policymakers in the past and present. Attending and participating in the conference offered the chance to see firsthand how delegates and other actors negotiate and deliberate to shape the future of our planet. Here, I reflect on the different ways that the past inflected these discussions, and how they resonate with the fields of climate and environmental history.

With Fiji presiding, the COP23 had the specific goal of preparing the implementation phase of the Paris Agreement. Having celebrated the achievements of Paris in 2015, now was the time to get down to work to ensure that the rise of global temperatures is limited to 2 Celsius or below. The organisation of COP23 was such that intergovernmental negotiations took place in the ‘Bula Zone’, while about two kilometres away in the Rheinaue Leisure Park was the ‘Bonn Zone’, where governments and all manner of non-governmental organisations showcased their work in events, exhibits, and demonstrations. I was granted access only to the latter; I gathered from colleagues and other participants that the distance between the two spaces was a shortcoming because it isolated negotiators from the energetic atmosphere in this area, while diminishing the transparency and openness of the negotiations.

In observing how national interests shape global climate policies, I was especially interested in representations of economic development, adaptation, and climate justice, and how these informed the discussions at the COP23. These issues are inherently historical in nature, processes spurred by global configurations of imperialism, capitalism, and (de-)colonisation since at least the eighteenth century. With the small island nation of Fiji as co-host of the meeting, these concerns were front and centre for the duration of the event. The strong cultural presence of Fiji in both the Bula (meaning ‘welcome’) and Bonn Zones ensured that there was both a sense of place and a sense of urgency to the negotiations. As the Fijian Prime Minister Frank Bainimarama reminded attendees on the eve of the conference, we are ‘all in the same canoe’.

COP23 hoardings outside the building that once hosted the Deutsches Bundestag. Photo by author.

Here, the inequities of anthropogenic climate change were palpable. Among the worst-affected by the increased frequency and magnitude of extreme weather events of a warmer planet will be those former colonies, such as the low-lying islands of the Pacific, that comprise the Global South. There is a dark irony, as Dipesh Chakrabarty and others have argued, that these peoples and places are bearing the brunt of a planetary phenomenon to which they have contributed little. They have received little of the benefits from economic growth associated with increased carbon dioxide emissions, but face the most immediate costs with the fewest resources to adapt. Having recently relocated the village of Vunidogoloa in the face of flooding and coastal erosion, and with plans to relocate many more, Fiji symbolized just what was at stake in Bonn.

The Adi Yeta on display in the Bula Zone. This drua is an 8-metre long traditional double-hulled, open ocean sailing canoe. Made from tropical hardwood and coconut fibre, the Adi Yeta was built in Suva, Fiji several years ago and was shipped to Bonn from the National Maritime Museum in Greenwich, UK. This drua will be permanently displayed in their new Pacific Encounters gallery in late 2018. Photograph courtesy of UNFCCC COP23.

The display and performance of the nation’s culture and history in both zones reinforced this symbolism. Each day, members of the Fijian delegation danced, sang and practiced traditional crafts and ceremonies, enlivening the conference with these colourful and moving expressions of ‘bula’ (also meaning ‘life’). The adoption of the Fijian and Pacific word ‘Talanoa’ to describe forthcoming facilitative discussions (the ‘Talanoa dialogue’) will hopefully ensure that this presidency leaves a lasting local impression on the UNFCCC process.

The attention to material culture continued on the conference fringe, with public art in the Rheinaue Park providing a meaningful connection between the Bula and Bonn Zones that underscored the urgent need for climate action. One striking piece created a ‘sign forest’ of rallying cries from past and current social and environmental campaigns. Suggesting the connection between these movements and the current climate crisis highlighted a sentiment I heard expressed throughout conference that ‘people power’ (and non-state actors) can give ‘confidence’ to governments to act on climate change. Another moving sculpture was ‘Unbearable’, by Danish artist Jens Galschiøt, which depicted a polar bear impaled on an oil pipeline curved upwards to represent increasing carbon emissions. These works, together with the fascinating Wetterbericht (‘Weather Report’) exhibition at the nearby Bundeskunsthalle, reinforce the important role of the arts and cultural institutions in ‘supporting conversation about and action on’ climate change, as the editors of Curating the Future argue.

What When by British artist collective Stan’s Café. Photo by the author

These exhibits combined with reports of a spike in carbon emissions this year, to remind us of just how far we had come and how far we had to go. At the Bonn headquarters of the UNFCCC, an exhibition celebrated over two decades of international climate change diplomacy, with Paris the crowning achievement to date. But others argued we had not come far enough: Uppsala University’s Zennström Professor Kevin Anderson despaired at the failure of “his” generation to curb emissions and to convince governments of the urgent need for action. Speakers turned to the past to reinforce their message. For Anderson, only an international effort on the scale of the Marshall Plan (1948-51) would come even close to meeting the aims of the Paris agreement. Others pointed to the Montreal Protocol (1989) and its impacts as an example of what could be achieved through international cooperation. These examples left me uncertain as to how instructive they might be for our current condition. On the one hand, they buoy our hopes that change can happen, while on the other, their circumstances suggest the key to action is an agreed threat – whether communism or CFCs. Amid the diffusion of expertise and authority that currently typifies Western liberal democracies, just how we can reach that common ground remains to be seen.

At the very least, these references to historic examples provided temporal markers to accompany the conference’s emphasis on the materiality of climate change. Fiji’s presidency and the displays of material culture that accompanied many delegations reminded participants that climate change, while a planetary crisis, manifests at the local level. The ‘sea of islands’ of the Pacific, the littoral, coastlines, were all sites where climate change was manifesting. Together, their evocation also suggested the importance of the physical properties of the ocean in our understandings of the climate crisis.

Although there was certainly plenty of techno-optimism in the air, many speakers and observers emphasised the importance of engaging with other forms of knowledge. One project involved sharing the fire cultures of Aboriginal Australians with local peoples in Botswana. This initiative was one of many that reflected the meeting’s more inclusive approach regarding First Peoples, whose care for country was finally acknowledged as vital for climate change adaptation and mitigation efforts. FAO Director-General José Graziano da Silva, meanwhile, lamented the impact of the Green Revolution on the ‘old ways’ of agricultural production. Both moments spoke to the urgency of redressing the troubling legacies of ‘improvement’ and Western hubris, and for the empowerment of local peoples at home and abroad.

For many participants, such empowerment lay in their faith. Church leaders from the Pacific, Californian Governor Jerry Brown, and former Irish President Mary Brown, for instance, all reflected on the importance of their faith to themselves and to their communities. Worship offered a culture of coping that connected them to each other and to a higher power, while providing an existential framework to make sense of environmental challenges. They and others invoked Pope Francis’ 2015 encyclical on the environment as a source of inspiration and hope that emphasised climate justice for all.

COP23 was not without its contradictions. Just fifty kilometres away from the host city, for instance, is the site of one of Europe’s biggest sources of CO2 emissions: the large open-cast lignite coal mine near Cologne. Thousands of demonstrators converged there to urge the German government to phase out the mining activity and to deliver on its progressive climate rhetoric. Meanwhile, the Australian government proudly announced further contributions to climate change adaptation measures in Oceania, but were less inclined to discuss the future of the Adani coal mine or the health of the Great Barrier Reef. These examples alone speak to the complex knot of labour, energy and conservation that continue to stymie climate action.

Perhaps the greatest contradiction of them all was the sheer size of the meeting, and its accompanying carbon footprint. So great were the demands of hosting such a conference that Fiji was unable to hold the event at home. To the enormous infrastructure required for the meeting itself, add the toll of international travel of some twenty thousand delegates and observes – it all makes for an eye-watering sum. Many scholars in the sciences and humanities have long questioned the environmental ethics of conference travel (particularly by air), and are exploring alternative ways for meaningful and productive scholarly exchange. Geography certainly presents something of a challenge for Australian academics, but taking a more strategic and judicious approach to the frequency of my own travels will be an important start. Attending COP23 made it clear to me that learning how to live and work more lightly is a challenge I can no longer afford to ignore.

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Katrin Kleemann, Rachel Carson Center

This picture shows the river Skaftá. The village Kirkjubæjarklaustur is located on the other side of the river. The size of the buildings and trees gives you an idea of how wide the river is. It was vaporized and replaced by lava in 1783. Photo: Katrin Kleemann, 2016.

“June the 9th [1783] was a day of clear weather, during which the cloud [north of the mountains] quickly rose higher and higher. In the evening a great downpour fell from it. The flow of the river Skaftá, a stream so great that at the ferry site here horses had to swim some seventy fathoms to cross it, and which ran eastward along the Síða area, now began to decrease substantially, however. On the 10th […] the river Skaftá had dried up entirely, except for the water emptying into it from local streams. […] On the 12th the weather was clear, with a wind from the south. Now the flood of lava spilled out of the canyon of the River Skaftá and poured forth with frightening speed, crashing, roaring and thundering. When the molten lava ran into wetlands or streams of water the explosions were as loud as if many cannon were fired at one time. At first this fiery flood followed the main course of the river, and then spread over the banks, and out over the older lava fields which stretch out on both sides […].”
Jón Steingrímsson (1728-1791), local reverend, who wrote a diary

In June 1783, the residents of Kirkjubæjarklaustur, an Icelandic village, watched as the water of their local river Skaftá vanished and, days later, was replaced by a “fiery flood” of lava. They could not have imagined that this event would have consequences halfway around the globe, all the way to eastern Africa. It suppressed the Nile’s summer floods and thereby helped cause a famine in Egypt, where agriculture depends on those floods. That summer, the 27-kilometer long Laki fissure, remotely located in the Icelandic highlands to the southwest of Vatnajökull, Europe’s largest glacier outside the Arctic, began an eight-month-long eruption. It released the largest amount of lava of any eruption in the last millennium, as well as huge quantities of sulfur dioxide, fluorine, and other gases.

The consequences would be catastrophic for Iceland’s population. The eruption did not kill anyone directly, but Laki's gases, especially the fluorine, poisoned the fields and thereby killed a large percentage of Iceland's cattle, horses, and sheep. The people of Iceland, deprived of their main food source, soon suffered malnourishment and starvation. These “hardships of the mist“ - today remembered as móðuharðindin - lasted until 1785, and claimed the lives of about a fifth of Iceland's population. Some 10,000 people perished.

This image shows the position of Iceland and the direction in which the dry fog was blown; it also shows the position of the Mid-Atlantic Ridge and the three major volcanoes in Iceland. The Laki fissure is just southwest of the Vatnajökull ice shield. This map was created by Katrin Kleemann and is built upon map materials from Gingko Maps, which are licensed under a CC BY 3.0 license.

In the rest of Europe, a strange sulfurous-smelling "dry fog" lingered for around two months. The levels of sulfur dioxide in the atmosphere were comparable to present-day extreme air pollution events. In France and England, contemporaries reported sore eyes, skin irritations, respiratory problems, and damage to vegetation. Today, this dry fog is referred to as volcanic smog, or “vog,” and we know it can worsen cardiorespiratory illnesses. Volcanologist Anja Schmidt has used climate models to simulate what would happen if a Laki-style eruption occurred today. She found that excess mortality - that is, deaths that would not have occurred otherwise - would be 142,000 deaths within a year of the eruption.

In 1783, the news of a volcanic eruption in Iceland reached Europe only in September, after the fog had vanished. It took another decade for an Icelandic expedition to find the Laki fissure, and roughly one century for scientists to connect the dots between the eruption and the dry fog it caused. It would not be as long, however, before even bigger eruptions would have still more destructive consequences for human lives and livelihoods.

An image from NASA’s TOMS satellite on 30 June 1991, showing the global circulation of Pinatubo’s ash.

Volcanic eruptions can cause climate change if they release large amounts of sulfur dioxide high into the stratosphere. Sulfur dioxide oxidizes into sulfuric acid aerosols, which reflect incoming solar radiation. The troposphere, which is the atmospheric layer in which we live and in which our airplanes fly, experiences cooling, whereas the stratosphere, the layer above the troposphere, which starts at 18 km near the equator and around 9-13 km in the high latitudes, heats up. Other gases released from eruptions, such as carbon dioxide, are greenhouse gases and contribute to the warming of the planet. Yet overall, big eruptions that send sulfur dioxide into the stratosphere can cause profound, if relatively short-lived, cooling.

The biggest eruption in recent centuries was that of Tambora in 1815. It reached a 7 on the volcanic explosivity index (VEI), a logarithmic scale from 0 to 8 in which each level registers a tenfold increase in explosivity (measured in volume of ejecta and eruption height). By contrast, the eruption of the Laki fissure "only" reached a 4. Tambora exploded in present-day Indonesia, at a tropical latitude where trade winds - the persistent easterly winds north and south of the equator - helped to spread its aerosols around the globe.

Thanks to this global dispersal, evidence of tropical volcanic eruptions can be found in Greenland and Antarctica. Glaciologists study layers of compressed snow and bubbles of preserved air in ice cores to reconstruct the climate of the past. In the cores, they also find layers of ash, tephra, and gases such as sulfur - byproducts of volcanic eruptions - which help them to date the ice layers. High latitude eruptions such as the Laki fissure eruption only deposit ash and tephra in one hemisphere.

Tambora’s impact on Earth's climate was magnified as the volcano erupted in the aftermath of a very strong eruption in 1809 (VEI 6), which has not yet been localized. Both eruptions occurred in a period of low solar activity known as the Dalton Minimum (ca. 1790-1830). In 1816, Tambora therefore brought a bitterly cold "year without summer" to the Northeastern United States, as snow and frost ruined crops as late as June. Cooler temperatures and heavy rains also plagued Ireland and the rest of Europe, which helped provoke famine. Tambora also delayed the summer monsoon in India, where unseasonal and torrential rain helped cause flooding, crop failures, famine, and ultimately a cholera epidemic.

This figure is based on Michael Sigl et al. 2015. It shows large volcanic eruptions, which occurred in the tropics (green), in the northern hemisphere (red), and in the southern hemisphere (blue). This graphic was created by DeWikiMan, and it is licensed under a CC BY 3.0 license.

The graphic also shows that several volcanic eruptions can occur at around the same time, increasing their effect on the climate and thus their impact on societies. A series of volcanic eruptions coincided with the massive 1257 Samalas eruption in today’s Indonesia, for example, and the 1458 Kuwae eruption in today’s Vanuatu. Eruptions in quick succession, including in 1595 (Nevado del Ruiz in today’s Colombia) and 1600 (Huaynaputina in today’s Peru), caused a June-July-August temperature anomaly between 1600 and 1609.

In 2012, Gifford H. Miller was the lead author of an article that argued that large volcanic eruptions in the late thirteenth century might have initiated the abrupt onset of the Little Ice Age, which was then sustained for six centuries by so-called feedback loops between the ocean, sea ice, and the atmosphere. The climate system on Earth is sensitive to change and different parts of the system, solar radiation, sea ice, cloud cover, wind and ocean currents, are interconnected. One important feedback loop is the albedo effect, which relies on the fact that a white surface, such as ice, reflects more sunlight back into space than a dark surface, such as the ocean. When a series of strong eruptions at the beginning of the Little Ice Age cooled the global climate, sea ice and therefore the albedo effect increased, the Earth absorbed less solar radiation, and average global temperatures began a long and sustained decline. The resulting climatic shift was then reinforced by a series of large eruptions around 1458. Changes in solar radiation, Earth's rotation, and major patterns of oceanic and atmospheric circulation may also have contributed to the cooling, but volcanic eruptions were most to blame.

This figure illustrates the processes of the ice albedo effect, which in the present time is characterized by a warming and melting Arctic. During the Little Ice Age, the cycle was reversed.

The biggest concern of our present time is anthropogenic climate change and global warming. Interestingly, global warming is actually increasing the chances of volcanism in the cold parts on Earth. In many cold places, such as Iceland, there still are large ice shields, reminders of the last Ice Age, which are melting away in a warming world. The melting of these heavy ice shields takes away a weight, which causes an uplifting process of the land below, called the postglacial rebound effect. In volcanically active regions, the ice shields were resting on top of magma chambers, with the decrease of weight the magma chambers can produce more magma and grow, and thus making a volcanic eruption more likely than before. In most extreme cases, the constant melting of Iceland’s glaciers could lead to an Eyjafjallajökull 2010 size eruption every seven years.

Even a large volcanic eruption and a short-term cooling, similar to the Pinatubo eruption of 1991, would not change this warming trend in the long run. New research suggests that even a Tambora style eruption in 2085 would likely not offset global warming simply because the oceans will be considerably warmer than they were in 1815. Another recent paper by lead author Ingo Bethke revises climate models by including sixty potential but fictional, large eruptions over the course of the twenty-first century. Most models actually ignore the potential of such eruptions. Yet the paper concludes that future eruptions are “unlikely to mitigate long-term anthropogenic climate change.”

Today, in our warming world, there are international efforts to cut greenhouse gas emissions to tackle anthropogenic climate change. Yet some scientists are also exploring ways to alter the climate through geoengineering, in order to stop the anthropogenic warming spiraling out of control. There are two different geoengineering categories: the first involves the removal of greenhouse gases such as carbon dioxide emitted by burning fossil fuels from the atmosphere, while the second involves managing solar radiation. Schemes in this second category would initiate a process of making the planet absorb less solar radiation to offset the consequences of the large-scale fossil fuel emissions of the recent past and present.

Geoengineers pursuing projects in this secondary category have been inspired by the cooling consequences of volcanic eruptions. However, the onset of the Little Ice Age, and the Nile floods that accompanied the small Icelandic eruption in 1783, both reveal the risks of such geonengineering schemes. The climate system is interconnected and incredibly sensitive to change. Reproducing the effects of a large volcanic eruption is both risky and dangerous, since we cannot know all the implications and potential consequences of such an endeavor. The long history of volcanic disasters therefore provides a warning for our warmer future.

This image shows the northeastern part of the Laki Fissure as seen from Mount Laki, extending towards the Vatnajökull ice shield. Photo: Katrin Kleemann, 2016.

Selected Works Cited:

Bethke, Ingo, Stephen Outten, Odd Helge Otterå et al. “Potential Volcanic Impacts on Future Climate Variability.“ Nature Climate Change 7 (2017): 799-805.

Cole-Dai, Jihong, David G. Ferris, Alyson L. Lanciki, et al. “Two Likely Stratospheric Volcanic Eruptions in the 1450s C. E. Found in a Bipolar, Subannually Dated 800 Year Ice Core Record.“ Journal of Geophysical Research: Atmospheres 118 (2013):7459-7466

Courtillot, Vincent. “New Evidence for Massive Pollution and Mortality in Europe in 1783-1784 may have bearing on global change and mass extinctions.” Comptes Rendus Geoscience 337 (2005): 635-637.

D’Arcy Wood, Gillen. Tambora. The Eruption that Changed the World. Princeton: Princeton University Press, 2014.

Fasullo, J. T., R. Tomas, S. Stevenson, et al. “The Amplifying Influence of Increased Ocean Stratification on a Future Year Without a Summer.“ Nature Communications 8 (2017). Doi: 10.1038/s41467-017-01302-z

Grattan, John, M. Durand, and S. Taylor. „Illness and Elevated Human Mortality in Europe Coincident with the Laki Fissure Eruption.“ In Volcanic Degassing, edited by Clive Oppenheimer, D. M. Pyle, and J. Barclay, 401-414. London: The Geological Society of London, Special Publication 213, 2003

Grattan, John, Roland Rabartin, Stephen Self, and Thorvaldur Thordarson. “Volcanic Air Pollution and Mortality in France 1783-1784.“ Comptes Rendus Geoscience 337, no. 7 (2005): 641-651

Lavigne, Franck, Jean-Philippe Degeai, Jean-Christophe Komorowski, et al. “Source of the Great A.D. 1257 Mystery Eruption Unveiled, Samalas Volcano, Rinjani Volcanic Complex, Indonesia.“ PNAS 110, no. 42 (2013): 16742-16747.

Longo, Bernadette M., W. Yang, J.B. Green, et al. “Acute Health Effects Associated With Exposure to Volcanic Air Pollution (Vog) From Increased Activity at Kilauea Volcano in 2008.” Journal of Toxicology and Environmental Health 73 (2010): 1370-1381

Manning, Joseph G., Francis Ludlow, Alexander R. Stine, et al. “Volcanic Suppression of Nile Summer Flooding Triggers Revolt and Constrains Interstate Conflict in Ancient Egypt.“ Nature Communications 8 (2017). Doi: 10.1038/s41467-017-00957-y.

Miller, Gifford H., Áslaug Geirsdóttir, Yafang Zhong, et al. “Abrupt Onset of the Little Ice Age Triggered by Volcanism and Sustained by Sea-Ice/Ocean Feedbacks.“ Geophysical Research Letters 39 (2012). Doi:10.1029/2011GL050168

Robock, Alan. “Pinatubo Eruption: The Climatic Aftermath.“ Science 295 (2002):1242-1244.

Robock, Alan, “The Latest on Volcanic Eruptions and Climate.“ EOS Trans. AGU 94, no. 35 (2013): 305.

Schmidt, Anja, Bart Ostro, Kenneth S. Carslaw, et al.: “Excess Mortality in Europe Following a Future Laki-Style Icelandic Eruption.“ PNAS 108, no. 38 (2011) :15710–15715

Schmidt, P., B. Lund, C. Hieronymous, et al. “Effects of Present-Day Deglaciation in Iceland on Mantle Melt Production Rates.“ Journal of Geophysical Research Solid Earth 118 (2013) :3366-3379.

Sigl, Michael, M. Winstrup, J. R. McConnell, et al. "Timing and Climate Forcing of Volcanic Eruptions for the Past 2,500 Years.“ Nature 523 (2015): 543-549

Sigl, Michael, and Matthew Toohey. ”Volcanic Stratospheric Sulfur Injections and Aerosol Optical Depth From 500 BCE to 1900 CE.” Earth Syst. Sci. Data 9 (2017): 809-831.

Steingrímsson, Jón. Fires of the Earth. The Laki Eruption 1783-1784, translated by Keneva Kunz, 25-26. Reykjavík: University of Iceland Press and Nordic Volcanological Institute, 1998.

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Dr. Sam White, Ohio State University.

In August 1559, the aspiring conquistador Tristán de Luna y Arellano brought some five hundred soldiers and a thousand colonists from New Spain to a settlement on Pensacola Bay, Florida, which he declared “the best port in the Indies.” The viceroy of New Spain reported to the king “the port is so secure that no wind can do them any damage at all.” Even as he wrote, a hurricane was entering the Caribbean, poised to devastate Puerto Rico. A week later, it roared into Pensacola Bay.

Tristán de Luna had no experience of tropical storms that could overwhelm even the strongest harbors. He had left all the settlement’s supplies aboard his ships in the bay. Food, clothing, arms, and armor all went down to the bottom of the sea with the wreck of his largest vessels. Only two small boats survived to take the sad news back to the viceroy in Mexico City. Within months, the colony unraveled amid hunger, exposure, infighting, and Native American resistance. When the survivors were finally evacuated, they came home complaining of Luna’s erratic leadership and the region’s “bad climate.”

Despite the scale of his expedition, and its chance to change the history of colonial America, few Americans today have even heard of Tristán de Luna. On the whole, that first century of European explorations and colonizing ventures in North America remains largely forgotten among the American public, more legend or Disney storytelling than real substance. That forgetfulness is a shame for two reasons, as I’ve come to learn my research. First, the real stories of those early expeditions are a lot more fascinating than the Disney version. Second, they present object lessons in the challenges of climate change that could be surprisingly relevant today.

"1559 Landing of Tristan de Luna at Pensacola." Herbert Rudeen, 1959.

Like many historians who study past climate and weather, I stumbled across my topic – the climate history of North America - by accident. As a graduate student, more than a decade ago, I was preparing a dissertation on the suitably obscure topic of agrarian crises in early modern Anatolia. What I discovered was that the Ottoman Empire, which then ruled the whole Eastern Mediterranean, had been unprepared for the onset of the coldest and (in that region) the driest phase of the Little Ice Age, from the late 1500s to late 1600s. Freezing winters and droughts, harvest failures and the death of livestock brought famines and undercut provisioning systems that the empire needed to supply its cities and armies. Soldiers mutinied; peasants and pastoral tribes rose up in rebellion; rural populations perished or fled; and the empire barely survived the chaos.

Published just as the Syrian civil war began, my first book, The Climate of Rebellion in the Early Modern Ottoman Empire, could have been a parable about the dangers of climate-driven conflict. Nevertheless, I was aware of the differences as well as the parallels between past and present. Neither the Ottoman crisis then nor the Syrian crisis now can be reduced to just climate change. Climate vulnerabilities have changed a lot in four centuries, in no small part because people in Ottoman times didn’t know that they were living through climate change. What we now recognize as the Little Ice Age was to them just a series of unforeseeable disasters. Today global warming is a much-discussed topic, and we all (should) know that climates are changing. Our challenge is how to imagine our future climates and adapt to them. So I wanted to find another historical example with parallels to our present situation.

That became one motivation to write a new book (left) about climate and colonial North America. When Europeans first came to the New World they weren’t expecting a change of climates. Received wisdom was that climates were more or less the same everywhere along the same latitudes. However, experience from the time of Columbus onward revealed that the Americas had different weather patterns and different seasons, even on the same parallels. The tropics were not the uninhabitable “Torrid Zone” that ancient authors had supposed them to be, while the continental seasons of North America turned out to be much more variable than in the maritime climates of Western Europe. The challenge for Europeans was to make sense of that change in climates and plan their expeditions accordingly. They had to decide where to explore or settle, what clothes to bring and crops to plant, often based on nothing more than rumors, hearsay, or passing observations.

Planners and promoters of these expeditions tended to fill the gaps in their knowledge with self-serving rationalizations. Early voyages in search of a Northwest Passage over Canada epitomized the problem. Every encounter with extreme cold or sea ice could be explained away as some local aberration or accident. Similar rationalizations led Spaniards to look for Mediterranean conditions and a “new Andalusia” in Georgia and the Carolinas, and inspired English visions of silk, spices, and sugar in Virginia and even New England.

For this reason, early European explorers and colonists were sure to be disappointed with the climates of North America. What turned disappointment into disaster were the extreme conditions typical of the Little Ice Age. On examining the range of proxy and written evidence for North American climates, I found the same sort of anomalies that caused trouble for the Ottoman Empire. The epic drought and extreme cold during Jamestown’s “starving time” of 1609-10 is only the most famous example. In the 1540s, Spanish expeditions in California, the Southwest, and Southeast all encountered freezing winters with heavy snows where they would rarely be found today.

A seventeenth-century depiction of the Jamestown colony, which settlers briefly abandoned amid a long drought.

Then from the late 1500s to the turn of the 17th century, a series of large volcanic eruptions brought global temperatures lower still. In 1601, for instance, the Rio Grande froze over near today’s Albuquerque; frost and drought brought famine to the Pueblos; and Juan de Oñate’s conquest of New Mexico nearly collapsed from hunger and desertions. French settlers in New England and Canada perished in the long winters that decade, and the little-remembered English colony at Sagadahoc, Maine gave up in 1608 after less than a year, its “hopes . . . frozen to death” in the words of one contemporary.

Cold and drought, as well as storms, afflicted colonial expeditions in different ways. Crops failed and animals died. Diseases spread from exposure, poor water supplies, and malnutrition. Long winters without fresh food brought scurvy. Supply ships were lost when needed most. Competition for food and fuel engendered conflict between European invaders and Native Americans, who also had to adapt to Little Ice Age conditions.

Yet evolving perceptions of North America’s climates were just as consequential as realities. Years or even decades of experience with parts of the continent did not always translate into realistic appraisals of their climates or accurate planning. Sometimes when the high hopes of early expeditions met the shock of unexpected extremes, they gave way to exaggerated disparagement and despair. Around the 1570s, after decades of disappointment, Spanish officials began to dismiss the whole of La Florida (today’s Southeastern United States) as “worthless,” and the near collapse of Spanish New Mexico left a similarly negative impression among officials in Mexico and Spain.

The failure of the Sagadahoc colony killed interest in New England for over a decade: “the country esteemed as a cold, barren, mountainous, rocky desert,” in John Smith’s words. Settlers in the Jamestown colony, however, refused to acknowledge Virginia’s environmental challenges. Their leaders blamed any problems on the colonists themselves and insisted the region was as temperate and fertile as anywhere in Europe. They became, in a sense, America’s first climate change deniers, sending thousands of colonists to early graves across the Atlantic.

The climatic vulnerabilities of the modern world may bear little resemblance to the struggles of isolated colonies four or five centuries ago. But human psychology has probably changed much less. It is easy now, as it was back then, to embrace denial or despair. It is a lot harder to adjust expectations, make new investments, or accept a different way of life than the ones we’re used or have planned on.

With Hurricane Harvey, the Houston area has just experienced its third so-called 500-year precipitation event in three years—and while it would be a mistake to write off the future of a city like Houston, it would be equally mistaken to imagine it can keep on going the way it has for the last generation. As we rebuild around Houston (and the next city to get flooded, and the one after that) it could help to compare ourselves to the early European colonists of North America. Even if we rebuild on the same locations, climatically speaking, global warming means we, too, have crossed into a new world.

3a:T27f5,

Dr. Laura Eerkes-Medrano, University of Victoria.

Sachs Harbour, photograph by Timkal. Available at: https://goo.gl/u7FWUB.

Global climate change brings with it local weather that communities and cultures have difficulty anticipating. Unpredictable and socially impactful weather is having negative effects on the subsistence, cultural activities, and safety of indigenous peoples in Arctic communities. Since 2013, Professor David Atkinson and his team at the University of Victoria have been working with Inuvialuit communities in Tuktoyaktuk, Ulukhaktok, and Sachs Harbour. The main goal is to understand how impactful weather is affecting residents’ subsistence activities, particularly when they are on the water. The project involves site visits, interviews, and regular phone calls with residents.

The Arctic study area. Google Earth, 2017.

Inuvialuit residents regularly observe the waves, winds, snow, and ice conditions that interfere with their hunting, fishing, camping, and other subsistence and cultural activities. In this project, communities identify specific weather events that impact their activities. These events are then linked to the broader atmospheric patterns that cause them. Summaries of the events will be provided to Environment Canada to hopefully assist with the forecasting process.

By taking this approach, the project links Western scientific knowledge and traditional knowledge to generate insights into how climate change is affecting Inuvialuit activities in the Canadian Arctic. An oversight committee has been established in each community to give direction to the project. This oversight committee includes representatives from each of the main community organizations, which ensures that the respective organizations provide direction to the project and advise on how to engage residents and communities.

Oversight committee members provide direction to the project. Photograph by LEM, Tuktoyaktuk, April 2016.

While the focus of the project is activities on the water, interviews with residents have shed light on a number of other impacts on their culture and subsistence activities. During a team’s site visit to Tuktoyaktuk in April 2016, the mayor, Darrell Nasogaluak, a member of the oversight committee, told me that “in the past, people were good at weather forecasting because they would observe the weather daily. Very few people today observe the weather as our forefathers did in the past, [who] would go out and look around and be able to predict the weather accurately. Now most people work Monday to Friday and only go out on Saturday and Sunday. Their only reference for what the weather will be like is the Environment Canada weather forecast, which is often not very accurate.”

Since they have only two days for outdoors activities, residents often go out even if the weather forecast is not very good. Their weather observations consist of taking a picture. Darrell Nasogaluak mentioned that in the past, people would remember what the weather was like and make connections to how it was on the preceding days. Residents would think about changes in wind direction and try to understand these changes and link them to potential causes.

“I would go out and I would ask someone what direction the thunders would be coming from, and they would know without looking at the window,” Darrell said. “Or I would ask when was the first storm this year and they would remember when it was in December. They would just have that knowledge. Now we go out and ‘click’ [take a photo] and don’t remember what it was like yesterday, and there is nothing to build on. That is how people are observing weather today.”

The oversight committee in action. Photograph by LEM, Tuktoyaktuk, April 2016.

On a larger scale, people have observed changes in timing and duration of storms. In Tuktoyaktuk, residents mentioned that big storms at the end of August and beginning of September are becoming more common. They cause stronger waves and affect their caribou hunt, as residents use their boats to go to the calving grounds at this time of the year.

One resident, Rita Green, explained that stronger waves have forced her to take part in the seal hunt, while her husband handles the boat. In the past, “only men hunted for seals, and these roles are changing,” she said during an interview in 2014. She also mentioned that on July 8 2017, she and her family faced strong west winds on their way back from Hendrickson Island, where they were hunting belugas, to Tuktoyaktuk. She said that it was very hard to navigate the 19-foot boat that she and three other family members were on. “It was so windy that waves were coming into the boat,” she said, “and we had to throw out some mutkuk and meat” to keep the boat stable.

Rita Green from Tuktoyaktuk demonstrating how she hunts for seals while her husband keeps control of the boat. Photograph by LEM, Tuktoyaktuk, March 2014.

During a phone call on July 8 2017, Vernon Amos, a resident of Sachs Harbour, said that spring 2017 camping activities in Egg River, which traditionally take place in May, were affected both by a lack of snow on the ground and by rivers running high with melt water. He added that winter blizzards were formerly not that common, but this past winter the community experienced one blizzard after another, and larger than usual amounts of snow.

By the end of April, warmer temperatures and strong winds caused the snow to melt quickly, which made it difficult to go camping using a snowmobile. On the way back from camping, residents had a hard time crossing the rivers. In the past these rivers would have been frozen, but now they were running high with water from melted snow.

Lack of snow on the ground made it hard to travel and set up camp using snowmobiles. Photograph: Vernon Amos, Sachs Harbour, May 2017.

Hunters in Sachs Harbour are concerned about the riverine erosion and permafrost degradation. As the permafrost dries it becomes very hard, which makes it difficult to travel by snowmobile. Another concern is the potential increase in tourism, particularly cruise ship activity, which could negatively affect caribou migration. On a positive note, the community’s fuel consumption during the winter of 2016 was 20 percent less than average, according to residents.

In Ulukhaktok, residents are concerned about the changes in winds and sea ice thickness. The sea ice used to form in October or November, but in the winter of 2016 it did not form until mid-December. With warmer temperatures the ice has less time to form, which makes it thinner and causes it to melt earlier. Residents used to go duck hunting, an important springtime subsistence activity, by driving their snowmobiles to cracks on the sea ice that ducks follow, and then driving another ten miles to gather duck eggs. One resident recounted how his father would take the snowmobile in July to go duck hunting. Now residents feel lucky if they can still use snowmobile for this activity in June. In 2017, residents had to take their boats instead.

Storm winds are also getting more intense. Where residents used to experience 30 to 50 km/h winds during storms, now the winds are reaching speeds of 50 to 70 km/h. People need to take more precautions while traveling. If the wind starts to blow while they are traveling by snowmobile, the sea ice can be very dangerous. Leads will open, and the east wind will take the ice away from the shore. according to residents interviewed during the spring of 2016.

There is now a great deal of information on how weather and in turn weather trends affect Inuvialuit activities on the water. This project is revealing that the impact of changing weather patterns is also felt across cultural and subsistence pursuits, and residents of the Arctic are having to adapt. Climate change is already affecting Inuvialuit lives in profound ways.

This project was funded by the Marine Environmental Observation Prediction and Response Network (MEOPAR).

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Christopher S. Kelly, Brown University, The Dwight-Englewood School.

Rwenzori Mountains of western Uganda: glacial valleys and gigantic Afroalpine vegetation at high altitude. Not pictured are the array of endemic fauna and local peoples who call these mountains home. Photo Credit: Dr. James M. Russell.

The Lukonzo word [spoken by the Bakonzo people] for their place, Rwenzururu, first misheard and mis-transcribed by H.M. Stanley in 1889, means the Place of Snow; and whether it is the reality or the symbol, Nzururu, snow is and remains the presiding deity.

When I first traversed the length of the range…not a day or a night passed without my and my Konzo companions’ awareness of the greater inner heights of snows and glaciers, the cradle of thunder and lightning. In every turn in the weather, there was the arm of Kitasamba. – Tom Stacey (Stacey, 2007)

Mount Emin. Mount Baker. Mount Stanley. It is rare for a location to excite so many disparate sensibilities, but the post-colonial scholar, glaciologist, botanist, and climate scientist find themselves welcome bedfellows in the Rwenzori Mountains in tropical central Africa, straddling the border between Uganda and the Democratic Republic of Congo (DRC). Even as far afield in time and space as ancient Greece, philosophers trafficked in rumors that the Nile Headwaters hosted Ptolemy’s snow-capped “Mountains of the Moon.” Equally famous today is the gigantism reached by floral species of heathers, senecios, helichrysums, and lobelias — some reaching heights of 12 meters.

Though far-flung from Eurasian loci of global power and empire, the mountains were named in ways that emblemize the crossroads of colony and metropole, from the brutal journalist-colonist Sir Henry Morton Stanley to Emin Pasha himself. More recently, the Rwenzururu separatist movement has been arguably the most persistent such conflict in post-colonial Africa. In this piece, I will illuminate the cultural significance of the mountains and glaciers within African and European history to contextualize the deep impact accompanying today’s rapid climatic changes. Admittedly, my motivations were aroused by close proximity to scientists presently working on the Rwenzori glacial and climate history—specifically, by a recent study just this year, which suggests that the scientific community may have grossly underestimated potential temperature change over these high mountains under current global warming (Loomis et al., 2017).

Lake Mahoma in the Rwenzori Mountains. The impacts of glacial melt and rising air temperatures could have dire effects on alpine lake ecosystems. Scientists interested in environmental change can parse out records of glacial and climate change from lake sediment. Photo Credit: Dr. James M. Russell.

The Roads to Rwenzururu

Histories in brief are precarious enough to begin on most continents, let alone our ancestral birthplace. But here, it suffices to relay the most recent peopling of the Rwenzori region, its foothills, and the Semliki Valley in the modern eastern Democratic Republic of the Congo (DRC). Beginning in the 7th century and continuing to just prior to the colonial period, waves of emigration out of the Sudan populated the Semliki Valley. Subsequent migration to the mountains seem to have coincided with environmental pressures, for example in the 1880s and 1890s when disease, drought, and state-level violence plagued the Semliki. Indeed, contrary to early colonial musings, the isolation of the modern Bakonzo people—the predominant tribe on the eastern flanks of the Rwenzori— is not ancient, but was instead prompted by an ascendant Toro state propped up by British colonial rule (located east of the mountains) and the massive loss of life due to warfare and disease in the Busongora plains and the Semliki Valley (adjacent lowlands) (Syahuka-Muhindo, 2007).

Today, the Bakonzo people primarily farm the eastern slopes. This practice signifies a split between the Bakonzo and other denizens of the Lakes region. Indeed, the economic consequences constitute one lens through which to understand the eventual unrest of the 20th century. One can trace the divergence back to the emergence between 800 and 1300 CE of specialized herding and banana cultivation in the Great Lakes region. These revolutions may have had an environmental origin, because dry periods would have forced pastoral productivity out of otherwise marginal land (Pennacini, 2007). Subsequently, new modes of production translated into farmer-herder client relationships for much of the broader Lakes region save the Bakonzo, Banande, and other nearby groups for whom the high altitude was not conducive to pastoralism.

When the British Protectorate of Uganda resurrected the Kingdom of Toro, the Bakonzo people were reluctant to enter the de facto monetary economy in a subservient position, and tensions flared. In combination with rampant disease in the early 20th century, a crippling British tax system, and exclusion from advancement within scholastic colonial education, conditions deteriorated to the point where Bakonzo gave flight. This exodus led many across the border to the Belgian Congo—a chilling punctuation mark given King Leopold II’s rightly earned infamy as purveyor of mass terror and slave-based economy in the Congo Free State (Hochschild, 1999). When the situation in the Rwenzori became untenable, the Bakonzo rebellion broke out against the Toro polity in the 1920s and 1960s. This culminated when the Rwenzori peoples unilaterally declared independence from Uganda in 1962 (Pennacini, 2007).

More than Mountains

For imperialists setting their eyes on them for the first time, the Rwenzori mountains prefigured into an already circumscribed map of geographical, cultural, and racial mythos. In the voracious Zeitgeist of late 19th century colonial ambition, the search for the mythical “single origin” of the Nile River became a quest not only to solve a long-standing geographical mystery, but to identify the origins of Western civilization (Wittenberg, 2007). Simon Schama clarifies that “rivers took on metaphor and coursed “as lines of power and time carrying empires from source to expansive breadth”(Schama, 1995).

When Henry Morton Stanley “discovered” the Rwenzori mountains in 1888, he took great scientific pains to show that they were indeed the primeval source of the Nile, and couched even their cultural surroundings within ancient Egypt. This would be an inexplicable falsehood without the context of European conceptions of Africa as a world apart, dark and barren and uniquely outside of civilization, and the mythological backstory in which the Rwenzori were already, in the minds of learned Europeans, connected to their own cultural development in antiquity. In other documents from the time period, “white snow” in “Darkest Africa” (the title of Stanley’s reports documenting his traverse) was irreconcilable without invoking separate geographical and cultural provenance (Stanley, 1890; Wittenberg, 2007). The first European woman to reach the alpine zone, Ruth Fisher, described Rwenzori as “the one unsullied and impregnable witness of holiness and purity to God, in a land where darkness has reigned, and the storms of passion, vice, and barbarity have laid desolate” (Fisher, 1919). To Fisher, and many in the colonial project, the mountains represented superior benevolence and nobility, concordant with Europe and European ideals (Wittenberg, 2007).

Others related the cooler temperatures and grassy fields of the alpine environment more explicitly to good health —for Europeans, that is. A prominent work of colonial fiction from 1906 by the British politician, colonialist, and author John Buchan imagines that “[mountains] will be what Simla is to India, the workshop of government…they are in another climate, and give a tired man the moral and physical tonic he needs” (Buchan, 1906) Another passage from the same work expounds that:

If only each hot country had been given a habitable mountain, they would be the only places in the world to live in. On the ordinary upland you dominate the flat country because you are higher up, but here we also look down on the plain because we are wholesome and cool and sane and they are fevered. We are a lighthouse to the whole of Equatoria, and if there were fifty other lighthouses in the Empire there would be no tropical problem. (Buchan, 1906)

Conversely, for the inhabitants of the mountains, the symbolism is equally poignant, but unsurprisingly occupies a wholly different cosmology, focused on spirituality and fertility. The word Rwenzururu itself means roughly “the place of snow,” and some Bakonzo interpret the ice as the frozen sperm of the mountain-dwelling god Kitasamba (Pennacini, 2007). Central to this belief system is the fertilization of Earth and Konzo society by the yearly snowmelt (Pennacini, 2007). As such, the icy mountains themselves are inseparable from Bakonzo belief systems, especially their embitha —"that unspoken sense of unity and uniqueness” (Stacey, 2007). For those who have worked in the mountains with the Bakonzo people, it is easy to testify to the sanctity conferred on the snowscape.

Brown University paleoclimate scientist Jim Russell explained to me that:

Each time we visit the mountains our Bakonzo guides explain to us the rules of the mountains which are imbued with a respect for the space. No pointing, no whistling, no singing. Rules are especially strict when it comes to water: no bathing, and many times when we have gone out on a lake in a boat our guides will offer food to the waters. (Russell, 2017)

Two historical European depictions of Africa showing the Rwenzori before it was actually spotted by Europeans. On the left from 1513, Martin Waldseemuller shows the Greek-fabled Mountains of the Moon giving rise to the more northerly African rivers as the only geographic feature in “Dark Africa” (citing interpretation from (Wittenberg, 2007)). On the right is a reproduction (of unknown year to this author) of Ptolemy’s figure included in "Geographia." In this work, much of North Africa is complete, if incorrect, including the then-hypothesized Mountains of the Moon. It is intriguing to compare/contrast these maps in their detail and degree of conjecture.

Ice in Retreat

But the natural state of the region is in dramatic flux, primarily a result of human activity. These mountains, which loom over 5,000 meters (well over 16,000 feet), host equatorial glaciers that are in rapid decline; since 1900, East African glaciers have lost over 80 percent of their surface area (Hastenrath and Kruss, 1992; Thompson, 2002). The full social and natural ramifications of this loss are still not clear, but they could well be disastrous. Firstly, modern foreign tourism revolves around ice climbing and observing the glaciers. In 1991, the Rwenzori Mountains National Park was established, and the Bakonzo were banned from hunting in the mountains by the Ugandan state. In “exchange” for these restrictions, guides and porters for tourists entering the mountains were to be hired solely from the local communities on the mountain slopes, chief among them the Bakonzo (Russell, 2017). The disappearance of the glaciers may impact tourism in ways that call this agreement into question.

Secondly, glacier retreat is known to strongly impact water resources in some mountain glacier regions, such as the Andes (Baraer et al., 2012; Mark, 2008; Mark et al., 2010). Glaciers act like a dam, accumulating snow in the wet season and releasing it as meltwater in the dry season. This buffers against strongly seasonal flows. Glacier retreat in the Andes is associated with an increase in the seasonality of river flows and a slight increase in the mean flow rate (due to the melting of “ancient” ice). Recent research suggests that snowmelt may not impact local river flows that provide water to indigenous communities as much as it has in the Andean highlands (Taylor et al., 2009); nevertheless, changes to the alpine lakes and surrounding ecosystems are likely to occur given the combination of melting ice and warming (Panizzo et al., 2008).

Finally, local environmental risks, such as slash-and-burn techniques, exacerbate threats to an ecosystem already fragile to climate change, and pose a barrier to ecotourism endeavors. Recent disasters drive this point home, such as the fire outbreak on Mt. Rwenzori in 2012 and the subsequent Kilembe Flood of 2013 (IFRC, 2014; Misairi and Ninsima, 2012; UNESCO, 2012). In this case, the wildfires in the alpine zone weakened the water holding capacity of the upper mountain valleys, which then flooded into the lowlands during the next rainy season. In sum, this environmental “moment” and the future of the Rwenzori motivates scientific efforts to probe geological, glaciological, and historical records for patterns that have governed the history of ice and environment in the Rwenzori.

Learning from Past Climate Change

The last instance in Earth history to experience appreciable changes in temperature with rising CO2 was during the global thaw following our Earth’s most recent glacial time (~20,000 years ago continuing into the earliest Holocene ~11,000 years ago) (Clark et al., 2012), making that time slice a potentially helpful scientific analog. The Rwenzori Mountains are no exception. Moreover, scientists are interested in specifically how the past local climates and glacier extent of tropical high-elevation belts differed from the present under different background climatic conditions, and what lessons we might glean from those dynamics under the future regime of persistent global warming. Accordingly, scientific teams are actively working to understand both Rwenzori environmental change during across the “deglaciation” (warming following the glacial state), as well as the last glacial climate itself to probe differences that may inform understanding about the future (albeit a different sign of temperature/climate change). .

To study such past climates, scientists build “proxy” climate archives to reconstruct the extent of ice, but also the factors behind glacial expansion, namely temperature (cold) and precipitation (dry). Similarly, glacial retreat can result from warm temperatures or regionally wet episodes, or some combination thereof. Studies of Rwenzori glacial moraines—accumulations of glacial debris—as well as lake sediment records suggest that ice expanded during cooler and drier conditions at the same time as Earth’s last glacial maximum (Kelly et al., 2014). A new high-profile publication by Loomis et al. (2017) based on geochemical reconstructions of past lake temperatures at multiple elevations has revealed that this cool time was enhanced in the Rwenzori via amplified cooling with elevation during this global glacial maximum.

Uncovering recent changes in glacial extent has been perhaps even more fraught, since investigation requires deconstructing the colonial archive and the assumptions embedded in it—which even when approximately accurate, lack a long-term perspective. For example, the present episode of glacial retreat had been thought to commence in ~1880 due to the waning wet period in the latter half of the 19th century in the Great Lakes region, as well as the legacy of colonial observation, which intensified in the late 1880s (Hastenrath and Kruss, 1992; Mölg et al., 2003). But in 2008, a research group found that siliciclastic material in lakebed sediments across the Rwenzori region correlated with the glaciation of those lakes (Russell et al., 2009). Because siliciclastic content was more or less stable from 1200 until 1870, the scientists concluded that for multiple centuries, fluctuations in ice have been relatively small in comparison to those experienced today (Russell et al., 2009). In this way, the European records of shrinking ice are not at all indicative of “normal” conditions over the 800 years. Finally, the timing of initial retreat is crucial; 1870 falls in a regionally wet time in the Rwenzori, suggesting that assumptions about the timing of glacial retreat in the region made on the basis of late ninteteenth-century observations are inaccurate.

Replotted %siliciclastic data from Lakes Upper Kitandara and Lac du Speke, with permission. As a proxy for the extent to which a lake was glaciated, these records depict relative glacial stability in the centuries leading up to the present decline beginning ~1870 (fluctuations in the early part of the last millennium should be interpreted with caution; see original scientific work). (Russell et al., 2009)

Taken altogether, some consensus is emerging that Rwenzori glaciers are melting today mostly as a result of rising air temperature. A recent study has revealed that temperatures in the tropics increased more dramatically at high elevations compared to low elevations during the last glacial maximum (Loomis et al., 2017). If we can expect the same today, in our warming world, it would spell amplified warming in the high-altitude Rwenzori mountains—warming that the glaciers likely cannot withstand. Indeed, a prominent study of ice core records from Kilimanjaro gives tropical African glaciers only another ten years (Thompson, 2002).

Conclusion: Snow-Capped No More

An essay on the Rwenzori in the Western imagination concludes:

Ironically, the hopes of local Rwenzori communities are not only linked to the return of peace [following conflict in the Great Lakes region], but also a continuation of colonial myths about the Mountains of the Moon. In order to draw tourists and attract development, the Rwenzori will in all likelihood continue to be inscribed with a Western history that obscures local cultural knowledge, traditions, and histories.” (Wittenberg, 2007)

Climate change may call this obfuscating history and the tourism it promotes into question. As time passes, the disappearance of the glaciers will render Stanley’s “lofty mountain king, clad in its pure white raiment of snow” a more distant memory (Stanley, 1890). Just what this portends for Bakonzo cosmology, mountaineering, and tourism is today unclear. Yet it is no small irony that modern Rwenzori could face grave climate challenges from the conquest, dominion, and industrialization of the world by the Global North—the same processes that gave rise to a dependence on foreign capital in the first place in this unique mountain kingdom.

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In article after article, academics, policy analysts, and journalists have told a similar story: climate change, by melting Arctic ice, is unlocking resources that could soon trigger war in the far north. They argue that the race to extract the vast reservoirs of oil and natural gas that lie under the vanishing ice – up to a quarter of the world’s undiscovered fossil fuel reserves, by some estimates – will likely provoke hostilities between Russia, the United States, and other nations with claims to the bonanza. The overall failure of early drilling efforts in the Arctic, it seems, is of little consequence.

These claims add a new twist to a vast and growing body of scholarship that links climate change to conflict. Academics working in this area often begin their work by showing that past climate changes reduced – rather than increased – the regional availability of some crucial resource, such as water, or grain, or fish spawning grounds. They then use diverse methods to trace the destabilizing social and political consequences of these resource shortages. Environmental historians, for example, have argued that falling temperatures and changing precipitation patterns in the seventeenth century led to poor grain harvests and famines that provoked rebellions in diverse societies the world over. More controversially, scholars in many disciplines have linked human-caused global warming to droughts that encouraged migration and ultimately conflict in twentieth-century sub-Saharan Africa. Far less attention has been directed at the ways in which more abundant resources might incite violence either within or between states.

In fact, those who make claims about the inevitably more violent nature of the future Arctic have rarely thought to consider the history of climate change and conflict in the far north. Yet violence in the Arctic has long coincided with volcanic eruptions and fluctuations in solar activity that altered regional temperatures and in turn the availability of crucial resources. In the early seventeenth century, for example, the Arctic cooled sharply and then warmed slightly just as Europeans discovered, hunted, and fought over bowhead whales off Spitsbergen, the largest island of the Svalbard archipelago. Oil, bones, and baleen from bowheads became crucial resources for the economies of England and the Dutch Republic.

Diverse manifestations of climate change in the Arctic and Europe influenced how easy bowhead whales were to hunt, the profits that could be fetched by their oil, the proximity of whalers to one another, and the ability of whalers to reach the far north. Skirmishes within and between whaling companies operating from rival European nations reveal that climate change can affect both the causes and the conduct of conflict in diverse ways, even in environments it transforms on a vast scale. There is nothing inevitable or simple about the ways in which climate change influences human decisions and actions.

Svalbard, roughly halfway between Norway and the North Pole. Spitsbergen is the big island on the left.

This history would be hard to investigate without new climate reconstructions compiled by scholars in many different disciplines, using many different sources. In 2014, researchers drew from natural and textual sources to create a sweeping new reconstruction of average Arctic air surface temperatures over the past 2,000 years. It confirms that the Arctic was overall very cold in the seventeenth century, but also that it warmed slightly towards the middle and end of the century. Temperatures in the Arctic therefore roughly mirrored those elsewhere in the Northern Hemisphere during the chilliest century of the “Little Ice Age,” a cooler climatic regime that endured for roughly six centuries. The extent and distribution of sea ice in the Arctic – the most important environmental condition that whalers coped with – would have responded to even subtle changes in average annual temperatures.

Yet these very big trends do not tell us exactly how climate change transformed environments around Svalbard. Local temperature trends do not always precisely mirror regional or global developments, and anyway the distribution and extent of Arctic sea ice registers more than just the warmth or chilliness of the lower atmosphere. Ice core and model simulation data both suggest that air surface temperatures around Svalbard were quite cool in the early seventeenth century and somewhat warmer in the middle of the century, at least in summer. Lakebed sediments, by contrast, suggest that glaciers across Svalbard actually retreated beginning in around 1600 owing to changes in precipitation, not temperature, which may have reduced the local frequency of storms that can break up sea ice. Moreover, sea surface temperatures – which also influence sea ice – were quite warm off the west coast of Spitsbergen, the largest island of the Svalbard archipelago, for much of the seventeenth century, although they were very cold off the northern coast.

A 2014 revision (red) of a PAGES 2K reconstruction (black) of annual average temperatures across the Arctic, compiled using diverse scientific and historical sources.

Overall, it seems safe to conclude that, in the summer, temperatures around Svalbard roughly mirrored those of the broader Arctic in the seventeenth century. Warmer currents may have brought more nutrients to the region and probably reduced the extent of local sea ice, although a reduction in storm frequency would have preserved the ice that was there. In any case, most Arctic sea ice melts in the summer before reaching its minimum annual extent in the fall, which means that summer weather and currents had the greatest impact on the extent of ice in the Arctic north of Europe. Because sea ice retreated from Svalbard in the summer, it was also the crucial season for whaling.

If the local consequences of global climate changes can be counterintuitive – that warming current off Spitsbergen, for example – so too can human responses. One might assume that climatic cooling would have dissuaded explorers, fishers, and whalers from entering the Arctic. Instead, European sailors found and then started exploiting the environments on and around Svalbard in the late sixteenth and early seventeenth centuries, just as volcanic eruptions led to arguably the coldest point of the Little Ice Age in the Northern Hemisphere. In previous work, I have shown that climate changes in this period interacted with local environments to leave just enough sea ice in the Arctic north of Europe to redirect expeditions in search of an elusive “Northern Passage” to Asia. Dutch and English sailors struggling to find a way through the ice ended up discovering Spitsbergen and the many bowhead whales off its western coast. Bowheads are relatively docile, float on the surface when killed, and have very thick blubber that can be turned into oil. Beginning in 1611, they started attracting Dutch, English, and Basque whalers.

Other scholars have argued that cooling in the early seventeenth century led bowhead whales to congregate along more extensive sea ice near Spitsbergen, which made them easier to hunt for whalers. By contrast, whales dispersed as sea ice retreated in the warmer middle of the seventeenth century, which made them harder to hunt. There does seem to be a statistically significant correlation between ice core reconstructions and model simulations of summer temperatures around Spitsbergen on the one hand, and the annual whale catch on the other. Iñupiat whalers consulted by our own Bathsheba Demuth, however, report that bowheads in the Berring Sea are not social enough to gather in huge groups. Perhaps bowhead culture was different in the Atlantic corner of the Arctic when whale populations were much higher than they are today.

Bowhead whales surface amid sea ice in the Beaufort Sea. Photo credit: Kate Stafford.

The apparent correlation between surface air temperatures and the whale catch around Spitsbergen provides our first point of entry into relationships between climate change and conflict in the far north. From the first years of whaling around Spitsbergen, two companies – the Dutch Northern Company, and the English Muscovy Company – emerged as the leading players in the Arctic whaling industry. The governments of England and the Dutch Republic had granted these companies monopolies on whaling operations, but they were resented by merchants and mariners who preferred to operate independently. After around 1625, as bowhead whales dispersed amid warming temperatures, competition between Dutch whalers devolved into piracy. Many conflicts involved whalers who sailed either for the Northern Company or for themselves, although even some Company whalers hid the best hunting grounds from one another. In these circumstances, the governing body of the Dutch Republic rescinded the monopoly of the Northern Company in 1642.

From the beginning, competition between English whalers assumed an even more brutal character. The Muscovy Company took an uncompromising stance towards English interlopers, who responded in turn. In 1626, for example, whalers aboard independently-owned vessels destroyed the Company’s station at Horn Sound, Spitsbergen, after they had been harassed by Company ships. Not surprisingly, petitions submitted to the English Standing Council for Trade in 1652 reveal that small groups of English merchants also sought to overturn the monopoly of the Muscovy Company. Individual merchants insisted that the Company could not adequately “fish” the territories over which it held a monopoly. The Company responded that whalers in the employ of those merchants had interfered with the activities of its sailors and stolen whales they had killed.

Warming temperatures that reduced the extent of pack ice and encouraged whales to disperse may well have encouraged competition and conflict between whalers belonging to the same nationality. Bizarrely, the whaling industry also responded to fluctuations in the supply of rape, linseed and hemp oils, which were less smelly substitutes to whale oil for fueling lamps or manufacturing soap, leather, or wax. Temperature and precipitation extremes that reduced the supply of vegetable oils naturally also increased the price of whale oils in the Dutch and English economies, and thereby the profitability of whaling. In the context of the Little Ice Age, the 1630s in particular were relatively warm across the Northern Hemisphere. The trusty Allen-Unger commodity database tells us that the price of linseed oil in Augsburg, for example, dropped sharply as average annual temperatures increased. Even the price of lamp oil – which would have also registered the price of whale oil – fell modestly in the same period. Could whalers in the 1630s and 1640s have vied with monopolistic companies just climate change both reduced the supply of their resource and increased its profitability?

A possible depiction of Smeerenburg (although another version of the same painting has Danish flags, and the mountain in the background resembles the volcano on Jan Mayen Island).

We can sketch these relationships by mixing and matching different statistics from natural and textual archives. Detailed qualitative accounts written by whalers, however, reveal that climate influenced conflict in more complicated ways during the first decade of the Svalbard whaling industry. In that decade, whalers from several European nations – most importantly England and the Dutch Republic – employed experienced Basque whalers to kill bowhead whales, strip their blubber, and boil the blubber on the coast. Whalers would deploy boats from a mothership to kill small groups of whales. They would then establish temporary settlements on the coast to turn the blubber into oil that could be loaded into barrels and returned to the ship.

These techniques forced whalers from different nations to rove along the coast of Spitsbergen, which made it likely that they would encounter one another. Initially, the Muscovy Company falsely claimed that English explorers had found Spitsbergen, which meant that it alone had the right to hunt for whales off the island. The Dutch – who had actually discovered the island – insisted that whalers from all European nations should be allowed to fish off its coast. In 1613, a Dutch expedition under Willem van Muyden, the legendary “First Whaleman” of the Republic, reached Spitsbergen in late May and found the coast blocked by ice. After only two weeks, the retreating ice let his whalers enter a bay roughly halfway down the island, but a better-armed English fleet quickly spotted them. In subsequent weeks, the English harassed the Dutch whalers and stole much of their equipment and whale commodities. Yet the Dutch returned with naval escorts in 1614. After the English seized a Dutch ship in 1617, the Dutch arrived with overwhelming force in 1618 and killed several English whalers.

Grønfjorden, Spitsbergen, where the hostilities of 1613 began.

The worst skirmishes between Dutch and English whalers raged in years that were relatively warm across the Arctic and probably around Svalbard, despite the generally cooler climate of the early seventeenth century. In cold years, sea ice could have kept whalers working for different companies from lingering on the coast, where tensions simmered and eventually erupted into bloodshed. In any case, the Muscovy Company and the Northern Company eventually agreed to occupy different parts of Spitsbergen. The Dutch would claim the northwestern tip, where they established the major, fortified settlement of Smeerenburg: “blubber town.” The English, meanwhile, took the rest. The Dutch eventually benefited from being closer to the edge of the summer pack ice, where there were more whales to hunt.

Hostilities between the English and the Dutch in the volatile first decades of the Svalbard whaling industry convinced the Northern Company to keep a skeleton crew at Smeerenburg and nearby Jan Mayen island during the winter. If they could survive, they would keep Company infrastructure safe from springtime raids and provide valuable information about the region’s winter weather. In 1633/34, two groups of Dutch whalers overwintered at Smeerenburg and Jan Mayen. Regional summer temperatures may have been warming at the time, but winter temperatures across the Arctic were cooling, and 1633/34 was particularly cold. The Smeerenburg group survived the frigid temperatures and killed enough caribou and Arctic foxes to hold off scurvy. The Jan Mayen whalers endured until the spring, but they could not catch enough game to survive the ravages of scurvy. In 1634/35, the Northern Company tried again. This time, both groups died from scurvy, and the Smeerenburg whalers did not even make it to winter. Violent competition between whaling companies – plausibly influenced by warming summers – exposed whalers to a quirk in the climatic trends of the Little Ice Age in the Arctic: the big difference between summer and winter temperatures, relative to long-term averages.

Climate change also influenced hostilities between whalers by altering how easily they could reach the “battlefield” around Spitsbergen. In 1615, a year of typical chilliness during the Little Ice Age, the author of a Dutch whaling logbook reported that sea ice on June 7th blocked the crew’s progress towards Svalbard. The crew spotted a bowhead whale three days later, but ice kept them from pursuing. That evening, a storm rose just as they found themselves surrounded by sea ice. They tried to anchor themselves to an iceberg, but it shattered and would have destroyed their ship “had God not saved us.” The few surviving logbooks written by Dutch whalers also record trouble with ice in the warmer 1630s, yet it surely would have been harder to reach Svalbard and compete with English whalers in the first decade of the Arctic whaling industry.

Dutch whaling logbook written on a voyage to Spitsbergen in 1615.

Beginning in 1652, the Dutch Republic and England also embarked on hostilities in the North Sea region that would endure, with interruptions, until the Dutch invasion that launched the Glorious Revolution of 1688. During the three Anglo-Dutch Wars that raged in these decades, English and Dutch ordinance kept whalers from sailing to the Arctic or constructing new ships and equipment for the whaling industry. Sailors who might have served aboard whaling ships were urgently needed to crew the warships of the English and Dutch fleets. Many whalers also served as privateers, raiding merchant ships and convoys and then surrendering a share of the profits to their governments. Any whalers who set sail for the Arctic risked losing everything if discovered.

As I have written elsewhere, a cooling climate in the second half of the seventeenth century profoundly influenced naval hostilities between the English and Dutch fleets. By altering the frequency of easterly and westerly winds in the North Sea, it helped the English claim victory in the First Anglo-Dutch War but aided the Dutch in the Second and Third Anglo-Dutch Wars, as well as the Glorious Revolution. It probably shortened the First Anglo-Dutch War (1652-54) but lengthened the third war (1672-74). That, in turn, would mean that the manifestations of global climate change in the North Sea affected the opportunities for whalers to engage in hostilities in the Arctic.

Ordinance forbidding whaling issued by the States-General, the Dutch ruling body, in 1673.

After 1650, the character of hostilities between Arctic whalers changed dramatically. Cooling summer temperatures brought thick ice into the harbors of Spitsbergen, while the depletion of the bowhead whale population may have worsened the prospects of whaling near land. Whalers had to hunt further and further from the shore, and started processing their whales at sea. They abandoned settlements along the coast of Spitsbergen, which soon fell into ruin. Violence between whalers now took place exclusively at sea. The evidence is spotty, but privateers seem to have hunted whalers in the final decades of the seventeenth century. In 1692, Henry Greenhill, commissioner of the English navy at Plymouth, reported that two “Greenland Prizes” – whaling vessels captured off Spitsbergen – had been brought into harbor. Since England had allied with the Dutch Republic against France, these ships were probably French in origin.

The history of climate change, whaling, and violence in and around Svalbard during the seventeenth century is above all complicated, filled with surprising twists and turns. Climate change may have occasionally provoked violence, but it probably did so by reducing, rather than increasing, the accessibility of bowhead whales to whalers. More importantly and more certainly, it altered the character of confrontations between whalers in the far north. Moreover, its manifestations thousands of kilometers from the Arctic ended up having important consequences for hostilities in and around Svalbard.

These intricate relationships in the distant past should give us pause as we contemplate the warmer future in the Arctic. Global warming may indeed set the stage for war in the far north, but we have no way of knowing for sure. It is equally likely that climate change will provoke human responses that are hard to guess at present. In this case, we cannot use the past to predict the future, but we can draw on it to ask more insightful questions in the present.

~Dagomar Degroot

Selected Works Cited:

Degroot, Dagomar. “Exploring the North in a Changing Climate: The Little Ice Age and the Journals of Henry Hudson, 1607-1611.” Journal of Northern Studies 9:1 (2015): 69-91.

Degroot, Dagomar. “Testing the Limits of Climate History: The Quest for a Northeast Passage During the Little Ice Age, 1594-1597.” Journal of Interdisciplinary History XLV:4 (Spring 2015): 459-484.

Degroot, Dagomar. “‘Never such weather known in these seas:’ Climatic Fluctuations and the Anglo-Dutch Wars of the Seventeenth Century, 1652–1674.” Environment and History 20.2 (May 2014): 239-273.

Hacquebord, Louwrens. De Noordse Compagnie (1614-1642): Opkomst, Bloei en Ondergang. Zutphen: Walburg Pers, 2014.

Hacquebord, Louwrens. “The hunting of the Greenland right whale in Svalbard, its interaction with climate and its impact on the marine ecosystem.” Polar Research 18:2 (1999): 375-382.

Hacquebord, Louwrens and Jurjen R. Leinenga. “The ecology of Greenland whale in relation to whaling and climate change in 17th and 18th centuries.” Tijdschrift voor Geschiendenis 107 (1994): 415–438.

Hacquebord, Louwrens, Frits Steenhuisen and Huib Waterbolk. “English and Dutch Whaling Trade and Whaling Stations in Spitsbergen (Svalbard) before 1660.” International Journal of Maritime History 15:2 (2003): 117-134.

Laist, David W. North Atlantic Right Whales: From Hunted Leviathan to Conservation Icon. Washington, DC: Johns Hopkins University Press, 2017.

McKaya, Nicholas P. and Darrell S. Kaufman. "An extended Arctic proxy temperature database for the past 2,000 years." Scientific Data (2014). doi: 10.1038/sdata.2014.26.

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Dr. Josh MacFadyen, Arizona State University

Weather factory? ADM Mill in Minneapolis, c1920. Photo: Minnesota Historical Society, MH5.9 MP3.1A

When Monsanto spent $1 billion in 2013 to purchase Climate Corporation, its climate data, and its algorithms for using machine learning to predict weather, everyone from farmers and insurance companies to technologists and The New Yorker concluded that agri-business believed the climate science consensus: climate change is real and it introduces real risks to business. One century earlier, another major Western agri-business (Archer-Daniels-Midland or ADM) produced their own cutting-edge weather and crop forecasts, mainly in an effort to reduce the risk of what it called “weather markets.” By investing in environmental knowledge production, these companies revealed how they understood both local environments and international climate sciences.

Historians know a great deal about early amateur and state organized meteorology and climatology, and a range of new works are emerging on the science of forecasting. However, the climate looks different when we examine it from the private sector. Business historians do so using company records and within the context of the firm. My study of the economy of knowledge in agri-business focuses on Archer-Daniels-Midland Linseed Company (ADM), a notoriously secretive company that started in Minneapolis and has since become one of the big five multinational firms in the agrifood sector. Its primary interest in the early twentieth century was not the highly-processed corn and soybean commodities it is known for today. Rather, ADM specialized in another oilseed altogether – flax.

Flax had changed from a European crop grown for linen to a predominantly American crop grown in the temperate grasslands of the northern Great Plains and the Argentine Pampas. It was produced mainly for its seed (linseed), which was pressed to make linseed oil, the principal ingredient in paint. Flax was very popular with farmers in the northern Plains, because it matured quickly and could be planted on newly broken fields on the frontier. ADM had relocated to Minneapolis precisely because of this growing western supply chain. When they got there, they realized they had a lot to learn about anticipating the weather and forecasting production in this harsh new environment.

The history of ADM’s response to price volatility, supply chain problems, and trade policies tells us about the way businesses understand climatology and develop environmental knowledge. Like the Climate Corporation, ADM was predominantly concerned with risk mitigation. And where there was risk there was profit. The linseed oil business included some of the leading names in the chemical sector, including Lyman Brothers in Montreal, the Rockefellars’ American Linseed Oil, Sherwin Williams, and Spencer Kellogg and Sons. These companies were major players, and they purchased flax seed from for their oil and paint operations from whatever part of the world would supply it. In the late nineteenth century, that was predominantly the northern Plains, but in the early twentieth century they found emerging markets in Argentina, Uruguay, and some older flax producing regions in Eastern Europe and India.

As a relative upstart, ADM found a niche in the globalizing industry by providing crop and other environmental information to the trade. The big players bought flax seed and flax seed futures in a massive grassland frontier (the Northern Great Plains, the Canadian Prairies, and the Argentine Pampas) with limited knowledge of those regions’ agroecosystems and even less about their climates. This article argues that crop knowledge was extensive and growing in the late nineteenth century, but climate knowledge was limited and retreating, because of underfunding and spurious theories about solar radiation. Meteorological forecasts were only good for 48 hours, and although Farmer’s Almanacs were very popular, their forecasting methods were secretive and studies have shown that they were really no more accurate than a coin toss.

In my study, I make two other conclusions based on a content analysis of the firm’s semi-public market reports circulated between 1911 and 1925, with a five-year gap starting in 1918. The first is that ADM created an early version of the Climate Corporation, focusing its attention on the growing conditions and probable outcomes of the flax crop. The records show that the company virtually ignored the European and Indian crops, knowing that those would likely enter UK markets before reaching their North American clients. Most of their weekly synopses were about crop conditions in the northern Plains, drawing from a network of crop agents, elevator companies, and other intermediaries such as state flax scientists. However, their interest in Canadian conditions decreased, and they increasingly focused on Argentina over this period. By the 1920s, ADM was reporting on Argentina almost as frequently as it mentioned the US.

Archer-Daniels-Midland circulars presenting crop data (percent of extant circulars).

The second finding was that the futures markets were more closely connected to natural systems than some historians of these “incorporeal” commodities have argued. Information systems like ADM’s circulars developed almost real time networks of crop and climate knowledge, but after a certain point these agri-businesses, conceded that futures trading was “purely a weather proposition.” Commodity futures became highly risky as overlapping harvest seasons approached, linseed oil producers depleted their reservoirs, and buyers attempted to determine which crop and weather forecasts were most tenable. This is precisely where we would expect to hear corporations arguing over comparative meteorological systems and the reliability of Almanacs, but these topics were almost never mentioned.

ADM realized that in the period between sowing and harvesting, the price of flax was “a weather market.” Their records show that businesses in the grain and oilseed sector created extensive knowledge networks to gather crop and some climate information in almost real time. Unlike the meteorological offices or the almanacs, ADM aimed for the respect of a much smaller business circle, and they therefore maximized data and minimized predictions. They mentioned US weather in about half of their circulars (less for other countries) and they predicted weather in very few of those cases. They were more bullish with crop forecasts, but the circulars show that they rarely reported weather forecasts. The weather that they did report was current conditions, and it was mainly in regards to the Northern Great Plains crop during the critical maturing and harvest months (June–September).

Archer-Daniels-Midland circulars presenting climate data (percent of extant circulars).

As my longer article on ADM’s response to uncertain climates outlines, the company was deeply invested in place, and its business decisions were shaped in part by its longer commitment to the Northern Great Plains. Its larger role in the knowledge economy was influenced by its position on crop and climate science; the company distrusted government crop forecasts and disregarded meteorological forecasts. ADM’s respectability depended on accuracy, but as the almanacs (and recent politicians) show, you don’t need to be accurate to be popular.

When agri-business ignored early twentieth century climatologists and created their own knowledge products, they signaled a distrust in science that proved to be well founded. In recent decades, we are seeing a completely supportive message from the private sector. Business signals its knowledge about the environment at many scales, from local family farms to the United Nations Framework Convention on Climate Change. When Reagan-era Secretary of State, George P. Shultz, and Climate Leadership Council president, Ted Halstead, recently advanced what they call The Business Case for the Paris Climate Accord, their message was simple. Since top US businesses support the Paris climate agreement, Donald Trump should embrace the broad consensus of climate scientists and remain at the table in Paris. Granted, their argument ignored the ethical and other humanitarian reasons for stopping runaway climate change and mitigating the harmful effects it will have on the biosphere, but when even corporations like Monsanto are spending billions to mitigate the risks associated from climate change it’s time politicians listened to the deafening message coming from all sectors.

Joshua MacFadyen, “Long-range forecasts: Linseed oil and the hemispheric movement of market and climate data, 1890–1939,” Business History 59:7 (October 2017). Published online, April 2017. DOI: http://dx.doi.org/10.1080/00076791.2017.1304915

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Dr. Kent Linthicum, Arizona State University

The caldera of Mount Tambora, formed in the 1815 eruption. Credit: Jialiang Gao.

The recent bicentenary of the Year without a Summer (1816) has brought that unusual intersection of geological forces, changing climate, and human history into focus again. The radical cooling brought on by Tambora’s eruption seems especially significant as modern societies face their own dramatic climate change, albeit in the form of radical warming brought on by industrialization.

Tambora’s eruption in 1815 is the most recent seven on the Volcanic Explosivity Index (VEI). The VEI scale rates eruptions from zero to eight. VEI sevens erupt roughly one-hundred cubic kilometers of material and occur infrequently: the next most recent seven, after Tambora, erupted in 1257. The large amount of ejected material from Tambora’s eruption cooled Europe by 1-2 degrees Celsius on average. The cooling caused the subsequent summer of 1816 to be so cold that it was hardly a summer at all. In an era of increasingly warm summers, a cooler one might sound ideal, but chilly weather led to a food shortages and starvation throughout the northern hemisphere.

Between April and May 1816, "Bread or Blood" riots erupted across East Anglia as the price of bread surpassed the wages of agricultural and industrial laborers. While food riots had a long history in Britain, industrialization, enclosure, and globalization increasingly safeguarded the nation's food supply by the early nineteenth century.

The Bread or Blood riots reveal that climatic shocks could still provoke famine and rioting in the nineteenth century, even in the country that should have been least vulnerable to them. They also show that contemporary media depicted the rioters with disdain, in ways that probably worsened official responses to them.

At the close of 1815, the United Kingdom had ended its wars with France, yet it embarked on a long struggle with disastrous weather. After an “extremely changeable” January, February was “unseasonably warm and moist,” lifting hopes that the season's crops might recover. Yet The Observer reported that both industrial and agricultural laborers were in “extreme distress” already.

By early May, a “Monthly Agricultural Report” in The Observer explained that conditions had not improved because “sun and warm weather are the great wants.” Prices were on the rise because of increased demand, speculation, and poor harvests throughout Europe. East Anglia experienced a roughly 33% increase in the price of wheat between March and May. Laborers were incapable of affording the prices of food and became desperate. They needed to eat but had no money, so protest became their only option.

Temperature anomalies across Europe in the summer of 1816, relative to the 1971-2000 average.

In the frigid spring of 1816, riots broke out around East Anglia. One of the first instances was on April 17th when a crowd assembled in Gedding and smashed some farming equipment. After that Wattisham, Hitcham, and Rattlesden experienced disturbances on April 24th; Needham Market and Swaffham Bulbeck on May 7th; Bury St. Edmunds on May 14th; Brandon on May 16-18th; Norwich on May 16-20th; Hockwold on May 17th; Feltwell on May 18th; Hockham on May 19th; Downham Market on May 20-21st; and finally Littleport and Ely on May 21-24th. On May 23rd soldiers and local militia arrived in Ely, and between then and the 24th, they forcefully suppressed the rioting. Despite the military presence, some rioting continued in East Anglia, but the Littleport and Ely riots were successfully subdued.

While the protestors had many reasons for agitating, their core motivation was survival. They demanded either food, money, a reduction in food prices, or all of the above. In Brandon, the protestors called for “Cheap Bread, a Cheap Loaf and Provisions Cheaper.” A woman at the protest reportedly demanded “Bread or Blood in Brandon this day.” One man admitted that the protestors “did not mean any injury but he could not live with his large family as things were, and they must have flour cheaper.” As many of the protestors were agricultural laborers, they broke agricultural machinery, presumably with the goal of taking back those jobs that the machinery would have eliminated.

The protesters felt they had no choice: they would have food or violence, because either way their deaths were imminent. William Dawson of Outwell, when asked why he was agitating, is reported to have said, “Here I am […] between Earth and Sky—so help me God. I would sooner loose [sic] my life than go home as I am. Bread I want and Bread I will have.” For the protesters, causing a disturbance was the only way to ameliorate their suffering. Yet not everyone perceived the disturbances as the desperate attempts of the poor to find respite from coming starvation. Some saw the riots as evidence of the moral failings of the lower classes.

“Economical humbug of 1816 or, saveing at the spiggot & letting out at the bunghole" (April 1816) by George Cruikshank. Here Cruikshank criticizes the government for what he perceives as an imbalance in spending. The Regent, Princess Charlotte, Lord Castlereagh and others are stealing public money for their own wants and desires, with very little money going towards “Public Service.”

The Times reported on the disturbances on May 21st, noting that the sheriff of Suffolk had arrived in London to request government aid to “restore tranquility.” The first disturbances, according to The Times, had been incited by “malicious [...] agents” who were likely “agricultural labourers.” While the paper acknowledged that the protesters demanded “a reduction in the price of bread and meat,” it still suggested that their protests had been illegitimate.

When the protests broke out again, The Times depicted the protesters as criminals and revolutionaries. They had apparently attacked the “houses of those persons who were obnoxious to them.” Protesters in one group carried a flag inscribed with “Bread or Blood” and spears. They “threatened to march to London.”

The Times reported on the 25th "that the disturbances in Norfolk and Suffolk are by no means at an end.” The paper detailed the movement of troops, and related a short narrative about a few magistrates who realized that the laborers’ wages were too low and raised them. This caused The Times to ardently hope that the changes made by these magistrates in Downham were “proof of considerate attention to the complaints of the lower classes [and] will excite a correspondent gratitude in the minds of the latter, and induce them to return to habits of peaceful industry and order.” The suggestion by the paper was that the onus was on the laborers to stop protesting because a few officials had responded to their concerns. In other words, the laborers should just wait, because the government would come to their aid.

A long article on May 27th dove into the economics of the issue. The Times weighed whether the government should step in to support local agriculture when manufacturers in the country were not interested in the product. The paper concluded that government should not intervene, and suggested that protestors are merely using the current high prices as a “pretense” for violence. The paper brushed off the concerns of the protestors in East Anglia, again suggesting that they were rioting for malicious reasons rather than desperation. The final report, on the 30th, reported the disturbances had ceased, thanks to the efforts of soldiers and the local militia.

The Times placed the blame for “much of the disorderly conduct” on the poor laws, a system of welfare for impoverished people in the United Kingdom. The paper suggested that the laws had led the poor to expect handouts, and when they did not get what they wanted they became unruly. The rioters were brought to trial between June 17th and 22nd. In the end five people were executed, five exiled to Australia for life, four exiled for a shorter sentence, and ten imprisoned for twelve months. Food prices remained high in England until 1820.

“The Elgin Marbles! or John Bull buying stones at the time his numerous family want bread!!” (June 1816) by George Cruikshank. Cruikshank criticizes the government again for spending money contrary to the public good. In this case purchasing the controversial Elgin Marbles from Lord Elgin. Screaming children in the image implore John Bull (a national personification of Great Britain like Johnny Canuck or Uncle Sam) saying "Don't buy them Daddy! we don't want Stones. Give us Bread! Give us Bread! Give us Bread!".

Humanity has long endured changes in Earth's climate. Today, many people in the developed world can, for the moment, insulate themselves from the worst consequences of a changing climate. Yet millions in the developing world especially do not have that luxury. The media can either encourage or discourage action to address their suffering.

In 1816,The Times’ reporting of the Bread or Blood riots reinforced the idea that the protesters were criminals and malcontents, that their demands were inappropriate or untimely. That reporting would only bolster the biases of those in control. So despite a compromise written up by the Ely magistrates to increase wages depending on the price of flour and the size of the laborer’s family on May 23rd, on May 25th Lord Sidmouth placed a one-hundred-pound bounty on those “unlawfully assembled” in the region.

The Bread or Blood riots are a reminder that climate insecurity has been the rule and not the exception in human history. Newspaper accounts of the riots reveal that the media not only described events but also helped shape them in ways that exacerbated the worst effects of climate change for the most vulnerable. Today, media depictions of citizens furious about their lack of clean food or water, protestors enraged by the seizure and pollution of their homes, and refugees displaced by drought and violence can similarly worsen the social consequences of global warming. We must have a media that fairly describes the impacts of climate on people around the world, and we must keep a critical eye on media in order to adapt to and perhaps mitigate climate change.

Sources

“Disturbances in Norfolk And Suffolk.” The Times, May 23, 1816, pp. 3. The Times Digital Archive.

“London, Saturday, May 25, 1816.” The Times, May 25, 1816, pp. 3. The Times Digital Archive.

“London, Monday, May 27, 1816.”" The Times, May 27, 1816, pp. 3. The Times Digital Archive.

“London, Thursday, May 30, 1816.” The Times, May 30, 1816, pp. 2. The Times Digital Archive.

“Monthly Agriculral Report.” The Observer, Feb 04, 1816, pp. 4, ProQuest Historical Newspapers: The Guardian and The Observer.

“Monthly Agricultural Report.” The Observer, May 05, 1816, pp. 4, ProQuest Historical Newspapers: The Guardian and The Observer.

Oppenheimer, Clive. "Climatic, Environmental and Human Consequences of the Largest Known Historic Eruption: Tambora Volcano (Indonesia) 1815." Progress in Physical Geography, vol. 27, no. 2, 2003, pp. 230-259, doi:10.1191/0309133303pp379ra.

Peacock, Alfred James. Bread or Blood: a Study of the Agrarian Riots in East Anglia in 1816.
Victor Gollancz, 1965.

Post, John D. The Last Great Subsistence Crisis in the Western World. Johns Hopkins University Press, 1977.

“Riots in Suffolk” The Times, May 21, 1816, pp. 3. The Times Digital Archive.

“Tambora.” Global Volcanism Program, Smithsonian Institution, 2013. volcano.si.edu/volcano.cfm?vn=264040

Ward, Peter L. “Sulfur Dioxide Initiates Global Climate Change in Four Ways.” Thin Solid Films, vol. 517, no. 11, 2009, pp. 3188-3203, doi:10.1016/j.tsf.2009.01.005.

“Yesterday the Princess Charlotte and her husband received congratulatory addresses from Salisbury and.” The Times, May 23, 1816, pp. 3. The Times Digital Archive.

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Dr. Ruth Morgan, Monash University

Non-tabular iceberg off Elephant Island in the Southern Ocean. Source: Andrew Shiva, Wikipedia.

Ice, or a lack of it, is an “icon” of anthropogenic climate change. Earlier this year, researchers reported that a rift in Antarctica’s fourth-largest ice shelf has accelerated and could soon cause a vast iceberg to fall into the sea. After the collapse of the ice shelf, the glaciers that once sustained it will run into the sea. Glaciers like these, Mark Carey has observed, have become an “endangered species” of the Anthropocene. Yet only a few decades ago, Antarctic ice was the hero in a visionary episode of the planet’s recent “cryo-history”.

In October 1977, scientists met at Iowa State University to discuss the latest findings in the emerging field of “iceberg utilization”. Eager to promote the cause was conference co-sponsor Prince Mohammed al-Faisal of Saudi Arabia, who flew an iceberg weighing over two tonnes from the Portage Glacier Field near Anchorage, Alaska to Ames, Iowa for the occasion – producing at least 7 tonnes of carbon dioxide over the 5,000km journey. One local couple, who brought with them plastic bags, a bucket, and an ice-pick to the iceberg’s unveiling, told the New York Times, “I don’t know what we’ll do with it – serve it in drinks, I guess. We’ll have a cocktail party”.

A series of US television news features documenting the Iceberg Utilization Conference, October 1977. Source: YouTube / Special Collections and University Archives, Iowa State University.

These stunts amused onlookers, but they were no laughing matter for the researchers studying the possibility of towing Antarctic icebergs to arid and semi-arid climes. Iceberg utilization was a tantalizing prospect for solving one of the world’s pressing problems: global water shortages. In their controversial study The Limits to Growth, the interdisciplinary research group the Club of Rome had earlier warned that the availability of fresh water was a limit to growth that “will be reached long before the land limit becomes apparent”. Bolstering this neo-Malthusian prediction were the widely reported droughts in the Sahel, the Ukraine, and the failure of the Indian Monsoon during the early 1970s.

An excerpt from the public affairs program, Dimension 5, which aired on WOI-TV in central Iowa, USA, October 1977. Panellists include Prince Mohamed Al Faisal of Saudi Arabia, Henri Bader, Daniel J. Zaffarano, Richard L. Cameron, and Ed Cronick. Source: Youtube / Special Collections and University Archives, Iowa State University.)

These anxieties were the focus of the 1977 United Nations Conference on Water in Mar del Plata, Argentina, where fresh water was declared a “scarce asset” that demanded coordinated resource development and management. Among the options discussed to increase water supplies were so-called “complex technologies” and “non-conventional methods”, such as seawater desalination. By the late 1970s desalination was already well established in Kuwait, and Saudi Arabia was eager to replicate its neighbour’s success. Leading this mission (at least until Antarctic icebergs beckoned) was the head of the Saudi Saline Water Conversion Corporation: Prince Mohamed al-Faisal. He shared his vision with the Christian Science Monitor, “Over a period, we would hope to change the vegetation and climate in some coastal areas”.

The Prince’s idea was several decades in the making. The prospect of using icebergs to modify local climates and to provide endless water supplies to the world’s thirstiest regions had emerged in the decade after the Second World War. In a 1949 class at the Scripps Institution of Oceanography in California, oceanographer John Isaacs had speculated on the subject, and later expanded on his thinking in the February 1956 issue of Science Digest. He proposed floating an Antarctic iceberg along the Humboldt Current to the coast of southern California from where it could supply water to Los Angeles.

The feasibility of such a scheme had been confirmed in 1969, when glaciologist Willy Weeks and geophysicist Bill Campbell surprised even themselves when they concluded that towing icebergs to arid lands was “within the reach of existing technology”. They based their calculations on a large tabular iceberg that was twice the size of the Great Pyramid of Giza, which was less likely to roll in transit and more likely to be found near the Antarctic than the Arctic. The optimum routes for towing such an iceberg, they suggested, were from the Amery Ice Shelf to southwestern Australia and from the Ross Ice Shelf to the Atacama Desert.

“Optimum towing paths between the Amery Ice Shelf and Australia and the Ross Ice Shelf and the Atacama Desert.” Fig. 8, Weeks and Campbell, 1973, p. 220.

In 1973, the National Science Foundation and the Rand Corporation sponsored a subsequent report on the feasibility of southern California for such a scheme. Antarctic icebergs could supply water for urban, industrial and agricultural demands, while helping to abate the growing thermal pollution of the industrialized region. According to their estimates, towing an iceberg from the Ross Sea to the Pacific southwest would be significantly cheaper than inter-basin water transfers and desalination. Furthermore, nuclear energy could be used, which would alleviate the need to use fossil fuels during a decade of uncertain oil supplies.

The possibility of endless water supplies was too good to ignore and the Saudi prince assembled experts from around the world to advance the field of “iceberg utilization”. His 1977 conference in Iowa attracted scientists from arid and semi-arid countries such as Egypt, Greece and Libya, as well as nations with polar territories, such as Australia, Chile and Canada. Nearly three quarters of the attendees were from the United States, most of whom were associated with the military-industrial-academic complex. They included researchers from the Jet Propulsion Laboratory, Tetra Tech International, the Lawrence Berkeley Laboratory, the US Army Cold Regions Research and Engineering Laboratory, and the Naval Weapon Centre.

The lone woman speaking at the conference was the pioneering meteorologist, Joanne Simpson from the University of Virginia, Charlottesville. Simpson had been director of the experimental meteorology laboratory of the National Oceanic and Atmospheric Administration and member of the Weather Modification Advisory Board. Two decades of studying the intersections of cloud physics with hurricane research informed her comparison of Antarctic icebergs to cloudseeding, as well as her study of the atmospheric impacts of iceberg utilization. Although towing an iceberg would cost more than cloudseeding, she estimated that its meltwater would more than make up for the expense. In icebergs, Simpson also saw a means to mitigate the toll of tropical hurricanes. Using an iceberg to lower the surface temperature of the ocean ahead of an advancing hurricane would help to reduce the destructive winds of the hurricane.

“Illustration of possible new approach to the hurricane mitigation aspect of weather modification. Hurricanes are known to diminish in strength when they move over cooler water, here shown hypothetically to be supplied by a melting iceberg.” Source: Fig. 5, in Simpson, 1978, p. 865. Artist: Tom Henderson.

Simpson was well aware of the credibility gap that such endeavours faced. In 1978 she wrote, “For meteorology as a whole, public overheated controversy on weather modification gives the entire profession an image of ridiculous bumblers or even charlatans”. But the opportunity to “serve humanity” outweighed these concerns and she welcomed alternative modification methods.

Despite the promise of iceberg utilization, its potential impact on local climates became one of the many reasons why the vision did not become a reality. In Australia, for instance, enthusiastic plans for the continent’s southwest were rejected in the mid-1980s on the grounds that an iceberg “parked offshore for several years” might affect the regional climate in unexpected and unwanted ways. Peter Schwerdtfeger, the scheme’s Australian proponent, lamented that its feasibility lay not in science and technology, but in “politically and economically based decisions”. He remained confident, however, that iceberg utilisation would occur when “individual nations recognise their obligations to the more thirsty segment of mankind” and choose to exploit the Antarctic icebergs that otherwise “melt pointlessly in the Southern Ocean”. According to this logic, the failure to take advantage of the icebergs was tantamount to wasting precious water resources.

The possibility of iceberg utilization was one of many post-war technological visions. The futurism and science fiction of the atomic age urged the exploration and exploitation of new planetary frontiers such as the deep ocean and outer space. In the Cold War context, measuring, monitoring and manipulating the physical environment on a global scale had the potential to fulfil both military and peaceful ambitions. The iceberg “visioneers” were bit players in a wider debate about the Earth’s future, one that pitted the constraints of ecological limits against the possibilities of technological innovation. Just as the atom offered an inexhaustible source of cheap energy, Antarctica was a cornucopia of renewable fresh water simply awaiting the application of human ingenuity. Four decades later, we are searching for ways to keep that water well and truly locked up.

Further Reading:

Al-Nakib, Farah, Kuwait Transformed: A History of Oil and Urban Life (Palo Alto, CA: Stanford University Press, 2016).

Behrman, Daniel with John D. Isaacs, John Isaacs and His Oceans (Washington, DC.: ICSU Press, 1992).

Carey, Mark, “The History of Ice: How Glaciers Became an Endangered Species,” Environmental History 12 (2007): 497-527.

Carey, Mark, M. Jackson, Alessandro Antonello and Jaclyn Rushing, “Glaciers, Gender, and Science: A Feminist Glaciology Framework for Global Environmental Change Research,” Progress in Human Geography 40, no. 6 (2016): 770-93.

Fleming, James R., Fixing the Sky: The Checkered History of Weather and Climate Control (New York: Columbia University Press, 2010).

Gosnell, Mariana, Ice: The Nature, the History, and the Uses of an Astonishing Substance (Chicago: University of Chicago Press, 2005).

Hamblin, Jacob Darwin, Arming Mother Nature: The Birth of Catastrophic Environmentalism (New York: Oxford University Press, 2013).

Harper, Kristine C., Make it Rain: State Control of the Atmosphere in Twentieth-Century America (Chicago: University of Chicago Press, 2017).

Hult, J.L. and N.C. Ostrander, Antarctic Icebergs as a Global Fresh Water Resource (Santa Monica, CA: Rand, 1973).

Husseiny, A.A. (ed.), Iceberg Utilization: Proceedings of the First International Conference and Workshops on Iceberg Utilization for Fresh Water Production, Weather Modification, and Other Applications, held at Iowa State University, Ames, Iowa, USA, October 2-6, 1977 (New York: Pergamon Press, 1978).

Jones, Toby Craig, Desert Kingdom: How Oil and Water Forged Modern Saudi Arabia (Cambridge, MA: Harvard University Press, 2010).

Leslie, Stuart W., The Cold War and American Science: The Military-Industrial-Academic Complex at MIT and Stanford (New York: Columbia University Press, 1993).

McCray, W. Patrick, The Visioneers: How a Group of Elite Scientists Pursued Space Colonies, Nanotechnologies and a Limitless Future (Princeton: Princeton University Press, 2013).

Rozwadowski, Helen M., “Arthur C. Clarke and the Limitations of the Ocean as a Frontier,” Environmental History (2012): 1-25.

Sabin, Paul, The Bet: Paul Ehrlich, Julian Simon, and Our Gamble over Earth’s Future (New Haven, CT: Yale University Press, 2013).

Schmidt, Jeremy J., Water: Abundance, Scarcity, and Security in the Age of Humanity (New York: NYU Press, 2017).

Schwerdtfeger, Peter, “The Development of Iceberg Research and Potential Applications,” Polar Geography and Geology 9, no. 3 (1985): 202-209.

Simpson, Joanne, “What Weather Modification Needs – A Scientist’s View,” Journal of Applied Meteorology 17 (1978): 858-66.

Sörlin, Sverker, “Cryo-History,” in The New Arctic, (eds.) Birgitta Evengård, Joan Nymand Larsen and Øyvind Paasche (New York: Springer, 2015), pp. 327-39.

Weeks, Wilford J. and William J. Campbell, “Icebergs as a Freshwater Source: An Appraisal,” Journal of Glaciology 12, no. 65 (1973): 207-33.

40:T45d6,

Patrick Gage, Georgetown University

A recent drought in Brazil. Source: Wall Street Daily.

People care about climate change when it affects them. That is why Pacific islanders fear rising sea levels more than the average American, and why many who live in coastal cities fear a projected increase in tropical cyclones more than those further inland. Yet the idea that an environmental change “over there” will not affect communities “here” actually makes little sense. History is rife with examples of human crises brought on by seemingly distant climatic events.

One of the clearest examples unfolded in late nineteenth century Northeastern Brazil (Nordeste). A powerful El Niño-Southern Oscillation (ENSO) event warmed the waters of the equatorial Pacific Ocean, changing atmospheric circulation in ways that brought extreme rain shortages to Brazil, and ultimately launched the nation’s first rubber boom. The Grande Seca, or “Great Drought,” of 1877-1878 not only killed hundreds of thousands of northeasterners (nordestinos), but also sparked massive internal migration. The latter proved particularly problematic for the state of Ceará, from which thousands emigrated. Cearenses thus provided rubber barons in nearby Amazonas and Pará an invaluable supply of cheap labor, which they needed to meet growing demand. By 1900, the country exported more rubber than any other commodity except coffee. El Niño therefore shaped the history of Brazil.

Northern (green) and Northeastern Brasil (orange). Source: Wikipedia Commons.

ENSO events affect the global environment on an irregular basis. Typically, Peru’s cold Humboldt Current flows northward along the South American coast before easterly trade winds push it west along the equator. Warmed by the sun, its waters increase in temperature as they approach Indonesia, making the western Pacific hotter than the east. El Niño reverses these trends: trade winds and the Humboldt’s westward flow subside, westerly winds pick up, Kelvin waves carry warm water from Asia to South America in a process called “advection,” and hot, humid air masses travel toward Peru and Ecuador. Sea temperature in the eastern equatorial Pacific subsequently rises, causing changes in precipitation across the Americas. While coastal Peru faces torrential rain, Brazil’s Nordeste experiences severe drought. The distrinct relationships, or teleconnections, between ENSO and local climates generate different phenomena depending on the region. When Western Canadians enjoy an unusually warm winter, for example, Western Europeans may endure an especially cold one.

El Niño and drought in Northeastern Brazil therefore often coincide, but not always. The Brazilian Northeast has struggled with intermittent drought for centuries. Although its sugar- and cotton-heavy coast generally receives sufficient rain, the region suffered no fewer than forty-four unique dry spells between 1557 and 1992, or approximately one every ten years. Removing an abnormally wet period from 1615-1691 reduces that average to once per eight. What is more, of the fifteen so-called “major” droughts—those spanning at least two consecutive summers—only six occurred before 1800, implying a quantitative and qualitative increase over the past 200 years. While some of these dry spells occurred in concert with ENSO, many did not. Water shortages plague the Nordeste regardless of ocean temperature.

Different droughts affected the water-dependent Northeast differently. Though many were forgotten, some left indelible marks, none more than the Grande Seca. From 1877 to 1878, two “very strong” El Niño years dramatically increased water shortages and decimated the Nordeste, killing livestock and people by the tens of thousands. Ceará suffered most. As cattle and crop losses wiped out food supplies, the state’s death toll mounted. By 1878, 175,000 Cearenses had perished. All told, at least 500,000 nordestinos died and three million fled their homes. Newspapers from Ceará described the tragedy in heart-wrenching detail.

Young victims of the Grande Seca in Ceará, ca. 1877-1878 Source: Wikipedia Commons.

On 6 January 1877 (mid-summer), Cearense noted the first signs of hardship: “The lack of rains is already being felt. From Sobral and other … points of the province they tell us … the drought is … causing considerable damage.” Desperate letters painted a dismal picture. On 11 March, one man in Crato wrote: “We are with a terrible drought … and only God knows how painful this scourge will be.” Relayed another from Caixoçó: “The drought is ravaging everything, the mortality of cows is astonishing.”

The situation did not improve as March and the late rainy season became early winter. One correspondent from Assaré feared complete human annihilation in the surrounding countryside, while O Retirante (“The Refugee”) lamented the “emaciated bodies of our little children, wives and fathers.” A letter published several days before Christmas ended 1877 on a depressing note: “Already we are in the middle of December and not any rain! The drought with all its procession of horrors proceeds, threatening to swallow everything.”

The Grande Seca officially ended in 1878, but its effects lasted far longer. The drought crippled Northeastern sugar barons, who had watched their investments wither since the early 1800s. Cotton growers, whose business boomed during and after the American Civil War (1861-1865), likewise faced renewed headwinds, while cattle ranchers counted their losses in the hundreds of thousands of heads. The deadliest drought in Brazilian history, exacerbated by two consecutive years of exceptionally strong El Niño, therefore had a significant economic impact on the Nordeste, draining it of much-needed capital and contributing to the region’s lackluster development.

Above all, drought victims needed jobs, especially in Ceará. As an 11 March 1877 letter from Icó indicated, people often died “not because there [was] an absolute lack of foods, but because there [was] nothing with which to buy them.” Millions of desperate Cearenses therefore migrated to major population centers, hoping to find work. Among emigrants’ limited options, Brazil’s burgeoning rubber industry proved particularly appealing, both for its relatively high wages and geographical proximity.

Based in the Amazon Valley, namely the states of Amazonas and Pará, Brazilian rubber production did not begin until the late 1700s, after French explorer Charles Marie de La Condamine first watched natives use a “milky, viscous liquid” from the Hevea Braziliensis tree to make boots, toys, and bottles. Fueled by what amounted to a minor “gold rush,” exports of raw rubber and rubber products grew steadily through the early 1800s. The trade took off when Charles Goodyear discovered vulcanization in 1839, which made rubber resistant to extreme temperatures. Exports jumped from 388,260 kg in 1840 to 2,673,000 kg in 1860. Nevertheless, rubber remained largely irrelevant in Brazil until its first boom in the 1880s, when price increases and an influx of cheap labor pushed the commodity’s export share to 10 percent. That number soared to 39 percent by 1910. Brazil’s natural claim to Hevea made it the world’s largest producer for three decades

Brazilian rubber, ready for export, ca. 1900s. Source: Cancela, 2012.

Despite remarkable success, Brazilian rubber barons faced constant labor shortages throughout the late nineteenth and early twentieth centuries. The Grande Seca thus benefitted them immensely. Starving Cearenses, whom the rubber industry “desperately needed,” cared little about working conditions as long they were paid, and so accepted jobs few others dared to take—among them tapping Hevea trees in a hot, disease-ridden rainforest.

During the Grande Seca, Ceará became a key state for labor recruiters from Amazonas and Pará. In 1916, Joseph Woodroffe, a European eyewitness, claimed immigration to the Amazon Valley consisted exclusively of Cearenses, largely in response to the drought. Weinstein, Barham and Coomes, Caviedes, and Resor also acknowledge the Grande Seca’s role in driving poor Cearenses to the jungle, where they supported plantations as cheap tappers (seringueiros). But despite catastrophic death tolls from 1877 onward, emigration did not find universal support in Ceará. On the contrary, Cearense and its editors openly opposed the state’s depopulation for economic and humanitarian reasons.

Cearense arranged the debate as follows. On 15 April 1877, an “enlightened friend” in Sobral noted: “We continue to think … one of the most useful ways of applying aid, to which the State is obligated, would be … to promote seriously the emigration of our population to more fertile and almost unpopulated regions of other provinces.” Several pages later, however, a sordid column lamented the fact that thirty refugees had recently arrived in Fortaleza, Ceará’s capital, and hoped to reach the Amazon Valley. “This idea of emigration to other provinces,” the author mused, “is of incalculable disadvantages to Ceará.” Cearense’s publishers agreed, as future editions only “supported” emigration insofar as they acknowledged opposing views and occasionally allowed independent writers to criticize their claims.

The paper solidified its stance on 18 April. Emigration to Amazonas and Pará, it argued, was “harmful … to [Ceará] … because it [ripped out] a large number of strong arms for plowing.” Over the next seven months, such fear came up time and again. In July, for example, one writer professed concern for the state’s future: “…supposing [the drought] is transitory, how will we repopulate our deserted hinterlands if we remove … by means of a broad emigration, their natural habitants?” Together, these columns typified a standard economic argument against outmigration, namely that Ceará would need people to rebuild once the Grande Seca passed, and therefore could not absorb any more losses than necessary. But this only explains some of Cearense’s hostility toward open borders.

Though principally worried about Ceará’s financial prospects, educated nordestinos also expressed sympathy for destitute workers. Cearense printed articles throughout 1877 noting that rubber jobs in Amazonas and Pará were difficult and exploitative. On 18 April, the paper published several letters from Father José Thomaz, “who painted with blackest colors the luck of the poor emigrant, who is there [in the Amazon] reduced to the hardest and cruelest captivity by the rubber tappers to whom he hires his services.” Another pundit claimed Cearenses who left for Amazonas would likely “perish in the swamps.”

As more reports of emigration made their way into Cearense, so too did overt warnings. “Our wretched brothers who have gone to [Amazonas] have suffered horrible trials,” wrote one author on 18 October. Yet faced with certain death by disease or starvation, Cearenses continued to flee. By 23 September, at least 1,552 had crossed into the Amazon Valley, followed by hundreds more before the end of the year. Most left for rubber plantations.

Cearenses migrated by the thousands to Amazonas and Pará at the same time Brazil’s first rubber boom began (early 1880s). Those dates are no coincidence. While Amazonian elites owed their success to many different factors, drought-stricken nordestinos provided the foundation. Without adequate labor, there would never have been a rubber industry, let alone a profitable one.

Late nineteenth and early twentieth century Brazilian rubber production had far-reaching environmental consequences. When Emperor Pedro II created the province of Amazonas in 1850, Manaus, its capital, comprised little more than “a small collection of mud huts.” That changed rapidly as speculators flooded the region. The Amazonian North’s population quadrupled from 250,000 in 1853 to almost one million in 1910. Manaus and its Paraense counterpart, Belém, benefitted immensely: electricity, streetcars, exquisite theaters, and large ports graced the once-barren cities. Countless new rubber trails cut through the rainforest as well, in addition to increased traffic on the river. That said, the industry’s initial emphasis on wild Hevea trees delayed mass deforestation for several decades, while industrial cattle ranching, which would have required a dramatic physical reorganization of the Amazon Valley, lacked sufficient investment.

Droughts have shaped Northeastern Brazil for centuries, yet the Grande Seca stands out. Not only was it longer and drier than most, but it also came at a time of profound demographic and economic transformation in Brazil. That increased its death toll and its consequences for the human and environmental histories of Brazil.

The past, like the present, proves Earth’s interconnectedness. Environmental shifts “over there” will eventually affect us “here.” More than one hundred years ago, warming water in the Pacific Ocean changed the course of Brazilian history, driving extraordinary investment in the previously untapped Amazon Valley. In the same way, natural disasters, rising seas levels, and other symptoms of global warming will inevitably influence how all of us live our lives, regardless of geography.

There is no running away. We must face this crisis together.

Sources

Barham, Bradford L., and Oliver T. Coomes. Prosperity’s Promise: The Amazon Rubber Boom and Distorted Economic Development. Boulder: Westview Press, 1996.

Burns, E. Bradford. A History of Brasil: Third Edition. New York: Columbia University Press, 1993.

Caviedes, César N. El Niño in History: Storming Through the Ages. Gainesville: University Press of Florida, 2001.

Cearense. Fortaleza, Ceará. 1877. Available at: http://bndigital.bn.gov.br/hemeroteca-digital.

Glantz, Michael H. Currents of change: El Niño’s impact on climate and society. Cambridge: Cambridge University Press, 1996.

Gergis, Joëlle L., and Anthony M. Fowler. “A history of ENSO events since A.D. 1525: implications for future climate change.” Climatic Change 92, nos. 3-4 (2009): 343-387.

O Retirante. Fortaleza, Ceará. 1877. Available at: http://bndigital.bn.gov.br/hemeroteca-digital.

Pedro II. Fortaleza, Ceará. 1877. Available at: http://bndigital.bn.gov.br/hemeroteca-digital.

Quinn, William H. “A study of Southern Oscillation-related climatic activity for A.D. 622-1900 incorporating Nile River flood data.” In El Niño: Historical and Paleoclimatic Aspects of the Southern Oscillation, edited by Henry F. Diaz and Vera Markgraf, 119-150. Cambridge: Cambridge University Press, 1992.

Resor, Randolph R. “Rubber in Brazil: Dominance and Collapse, 1876-1945.” The Business
History Review 51, no. 3 (1977): 341-366.

Villa, Marco Antonio. Vida e morte no sertão: História das secas no Nordeste nos séculos XIX e XX. Editora Ática: São Paulo, 2000.

Weinstein, Barbara. The Amazon Rubber Boom: 1850-1920. Stanford: Stanford University Press, 1983.

Woodroffe, Joseph F. The Rubber Industry of the Amazon and How Its Supremacy Can Be Maintained. Edited by Harold Hamel Smith. London: T. Fisher Unwin and Bale, Sons and Danielsson, 1916. Available at: https://archive.org/details/rubberindustryof00woodrich.

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Dr. Bathsheba Demuth, Brown University

Most students at Brown University know Professor Kathleen Hess from the two-semester challenge of organic chemistry. But in a class that debuted this fall, “Exploration of the Chemistry of Renewable Energy,” Dr. Hess blended the tools of her discipline with questions of human impacts on the climate, renewable energy technologies, and the social impact of how energy is generated and used. The result is a socially-engaged course blending social science and bench science. “I thought this would be a perfect way to teach students who were not science majors,” Hess explains. “That was my goal.”

Courses on climate or energy history, renewable energy, and the relationship between climate and society are now taught at universities and colleges across the country. Most are designed by faculty in humanities, earth science, or engineering departments. Hess’s class offers a new model. Inspired by the Chemistry Collaborations, Workshops, and Communities of Scholars (cCWCS) pedagogy seminars, Hess's syllabus combines interdisciplinary readings, guest lectures, writing assignments - and laboratory experiments. “I wanted to give students both background on the topic,” she says, “and then give them the hands-on experiment so they would have practical experience.”

The course began by examining why renewable energy sources are increasingly important. Students read about fossil fuel pollution, climate change, and energy politics. They also did lab experiments to calculate how much energy is required to light a classroom. Then the syllabus moved on to examine batteries, fuel cells and solar panels. Hess framed each topic around a question. “Scientists should always be enquiring rather than saying we’re just going to the lab to make such and such,” Hess says. In one case, the class spent several weeks researching sources and uses of biofuel energy. Then students went to the lab to make fuel out of food waste from the Brown dining halls. “The students were really excited about this,” Hess notes. But when the class compared the energy yield to other fuels, “there was a lot of ‘oh, this is why we don’t do this,’” Hess says. “It was more of an illustration than just looking at another graph, because they saw and understood the processes involved.”

Students complete lab experiments in “Exploration of the Chemistry of Renewable Energy,”

In another case, students produced acid rain in a petri dish. Unlike history or policy classes, where acid rain is a topic – or most chemistry classes, where experiments are done in solution - Hess’s students saw “how concrete and bridges erode, and saw how materials travel through the air.” Students designed experiments to measure individual carbon emissions. In another experiment the class made their own hydrogen fuel cells. It required working with hydrochloric acid. Hess says hands-on exercises like this generated a great deal of student enthusiasm – not just energy between fuel cells – but were also complex and delicate. This was sometimes a challenge for students not used to the lab sciences. “Sometimes just getting ready to do the labs,” Hess says, “took some time and explaining. Sometimes they didn’t know how to start. So there could be a bit of inertia there.” Overall, however, Hess found “the level of student interest was really high. At the end of the course of the students told me that none of the lab assignments felt like homework, because they were so enjoyable.”

Across case studies, Hess linked the experiments back to social, political, and economic questions. Hess says her class arrived with “quite a few preconceived notions about why people believe in global warming or not, why they’re interested in renewable energy or not.” Through readings and lectures that covered climate change, the development of the current energy grid, the history of the electric car, the use of solar panel systems, and how humans have used different energy sources in the past, students started thinking about “how none of them have ever lived without power – without a light switch to turn on.” Student read about everything from global energy transitions to oil company correspondence about fossil fuel development. “I wanted them to see that we can always judge why people use the resources they do,” Hess explains, “but there are multiple sides to the story.”

Seeing these multiple sides helped students understand how the physical principles and technologies they were learning about in the lab “was one thing, but how to incorporate it into society is another,” Hess says. She had each student choose a renewable technology – from algal biofuels to concentrated solar – and design a brochure to convince consumers to use a new source of energy. Students also presented the results of their alternative energy research to the class. For Hess, this was the most inspiring part of the course. As each student learned to combine their technical knowledge from labs with their research on specific fuels, she says “they felt that was encouraging because they had to come up with an alternative energy to talk about, and knew collectively about all these different options.”

While thinking about climate change and the future is often discouraging and leaves individuals unsure how to respond, Hess found this course affirmed her sense that “education is the first step away from not knowing what to do. Especially mindful education where we don’t just judge things, but examine the combination of physical processes and assumptions that make them happen.” The best approaches to teaching climate change often combine perspectives from many disciplines, from the sciences to the humanities.

42:T41e3,

Dr. Dagomar Degroot, Georgetown University

Global temperatures in October 2016, relative to their average between 1951-1980. Source: NASA.

The world is warming, and it is warming fast. According to satellites and weather stations, Earth's average annual temperature will smash the instrumental record this year, likely by around 0.1° C. Last year, global temperatures broke the record by around the same amount. That may not seem impressive, but consider this: temperatures have climbed by about 0.1° C per decade since the 1980s. In just two years, therefore, our planet catapulted two decades into a hotter future.

Global climate change on this scale, with this speed, is unprecedented in the history of human civilization. Yet that history has still coincided with other, smaller but still impressive changes in Earth's climate. Humans may have played a minor role in some of these changes. The key culprits, however, were often violent explosions on Earth that coincided with periods of unusual solar activity. The most dramatic climate changes usually involved global cooling, not warming. The consequences for communities and societies around the world could be profound, in ways that offer lessons for our fate in a changing climate.

A tree ring summer temperature reconstruction of the Alps and the Altai Mountain over the past two millennia. Source: Büntgen (2016).

One of the coldest periods in the history of human civilization started in the early sixth century CE. Growth rings imprinted in the bark of trees suddenly narrow around 536 CE, and again around 541 CE. This narrowing reveals that trees practically stopped growing as Northern Hemisphere temperatures plunged by as many as 3°C, relative to long-term averages.

Other scientific "proxy" sources that responded to past climate changes reveal the same trend. A large team of interdisciplinary scholars, led by Ulf Büntgen, recently concluded that 536 CE was the first year of a "Late Antique Little Ice Age" - not to be confused with the better-known Little Ice Age of the early modern period - that chilled the Northern Hemisphere and perhaps the globe until 660 CE.

What could have caused this cooling? Cosmogenic isotopes tell us that solar activity had been falling for more than a century, as the sun gradually entered a "grand solar minimum." But that does not explain why Earth's climate changed so profoundly, and so abruptly, in the early sixth century CE.

Scientists now believe that ice cores containing traces of volcanic ash provide compelling evidence for a remarkable series of major eruptions, in 536, 540, and 547 CE. Big volcanic eruptions in the tropics can cool the Earth by releasing sunlight-scattering sulphur into the atmosphere. Trade winds swirling up from the equator bring this sulphur into both hemispheres, which ultimately creates a global volcanic dust veil. When eruptions happen in quick succession, Arctic sea ice can expand dramatically. Since bright sea ice reflects more sunlight than water, the Earth cools in response, which of course leads to more sea ice, more cooling, and so on.

Catastrophic volcanic eruptions, coinciding as they did with a prolonged decline in solar activity, may well have released enough aerosols into the atmosphere to usher in a much cooler climate. Yet sixth-century layers in Greenlandic ice cores may also suggest a very different, and even more exotic, culprit for climatic cooling.

Somehow, microscopic marine organisms of a kind normally found near tropical coasts ended up in ice layers that correspond to 536 and 538 CE. Layers dating from 533 CE also hold nickle and tin, substances that rarely appear in Greenlandic ice. Both metals are common in comets, however.

A team of scientists led by Dallas Abott recently concluded that dust from the tail of Halley's Comet may have started cooling the Earth as early as 533 CE. By reconstructing the past orbits of the comet, scientists discovered that it made a particularly close pass around the Sun in 530 CE. At around that time, Chinese astronomers recorded a remarkably bright comet in the night sky.

Earth regularly passes through debris left in the wake of Halley's Comet, and that debris might have been especially dense in the 530s and 540s. Meteor showers, therefore, may well have left cooling dust in the atmosphere, and metals in the ices of Greenland.

Tidal forces created by the gravity of a massive object - such as the Sun - can easily fragment cometary nuclei, most of which are collections of rubble left over from the primordial solar system. Dust released by such a breakup can dramatically brighten a comet. Perhaps that is what Chinese scientists witnessed in 530 CE, as Halley's Comet swung around the Sun.

According to Abbott and her coauthors, a piece of the comet may then have collided with Earth, launching sea creatures high into the atmosphere. Melted metal and gravity anomalies in the Gulf of Carpentaria off Australia suggest that an impact happened there sometime in the first millennium CE. At around the same time, aboriginal Australians etched symbols into caves that may well have represented comets.

An aboriginal Australian depiction of a comet (center), holding the Earth (left) and the moon (right).

It may well be that an extraordinary confluence of extraterrestrial impacts and volcanic eruptions, coinciding with a gradual fall in solar activity, chilled the Earth in the 530s and 540s CE. These dramatic environmental changes naturally astonished contemporary writers. In 536 CE, Procopius of Caesarea, a major scholar of the Eastern Roman Empire, wrote that the “sun gave forth its light without brightness, like the moon.” According to John of Ephesos, “there was a sign in the sun the like of which had never been seen and reported before in the world . . . The sun became dark and its darkness lasted for one and a half years."

A Syrian chronicler recorded that "The earth and all that is upon it quaked; and the sun began to be darkened by day and the moon by night." Chinese astronomers lost sight of Canopus, one of the brightest stars in the night sky. If there was a dust veil, it may well have been thick enough to obscure the heavens, whatever its origins.

Cassiodorus, a Roman statesman in the service of the Ostrogoths, wrote perhaps the most striking descriptions of the changes in Earth's atmosphere. "Something coming at us from the stars," he explained, had led to a "blue colored sun," a dim full moon, and a "summer without heat." Amid "perpetual frosts" and "unnatural drought," plants refused to grow and "the rays of the stars have been darkened." The cause, to Cassiodorus, must be high in the atmosphere, for "things in mid-space dominate our sight," and the "heat of the heavenly bodies" could not penetrate what seemed like mist.

Of course, we must guard against the assumption that observers such as Cassiodorus or Procopius simply recorded what they saw in the natural world. Descriptions of environmental calamities in ancient, medieval, and even early modern texts can be allegorical, representing social, not environmental developments. Still, many authors wrote eerily similar accounts of the real environmental upheavals in the 530s CE. To the modern eye, that of Cassiodorus in particular may seem to add evidence for a cometary cause of contemporary cooling.

An image of Comet 67P/Churyumov-Gerasimenko by the Rosetta space probe. Source: ESA

As temperatures plummeted and plants withered, communities around the world suffered. Scientists have examined pollen deposits that reveal sharp drops in the extent of cultivated land across Europe. Shorter growing seasons probably led to food shortages and famines that emptied once-thriving villages. Archaeological evidence suggests, for example, that Swedes abandoned most of their population centers in the sixth century, which were then swallowed by forests. Swedish survivors apparently created new towns in far smaller numbers, in upland areas removed from their former dwelling places.

Famines may have had particularly severe consequences across the densely populated Mediterranean. In 533 CE, just as cometary dust may have started entering Earth's atmosphere, the emperor of the Eastern Roman Empire, Justinian I, embarked on a costly campaign to restore the Western Empire. His subsequent wars in the Mediterranean, combined with a war against the Sassanid Empire that erupted in 540 CE, drew precious resources from the imperial countryside. As growing seasons declined, the demands of war compounded food shortages for millions of imperial citizens. Starvation spread through the empire, but worse was to come.

Malnutrition reduces fat-storing cells that produce the hormone leptin, which plays a key role in controlling the strength of the human immune system. In the sixth century, food shortages therefore weakened immune systems on a grand scale, leaving millions of people more vulnerable to disease. Those who survived famines also migrated to new towns or cities, increasing the likelihood that those infected with diseases would spread them.

Unfortunately for the inhabitants of what was left of the Roman Empire, Yersinia pestis, the pathogen behind the bubonic plague, was about to make its first appearance in Europe. From 541 to 542 CE, the “Plague of Justinian” swept through both the Western and Eastern halves of the Roman Empire, killing as many as fifty million people. In a warmer, more stable climate, the death toll may well have been far lower.

Not surprisingly, Justinian's campaign to retake the Western Empire stalled after the early 530s CE, although the reunified Roman Empire did reach its maximum extent in the 550s CE. Imperial resources were stretched thin, however, and European kingdoms reversed most of the new conquests soon after Justinian's death.

The empire of Justinian I at its greatest extent, in 555 CE. Source: Tataryn, 2012.

Climatic cooling probably had cultural consequences, too. There are signs, for example, that religious activity surged across Scandinavia as temperatures plunged. In times of crisis, devout Scandinavians offered gold to their gods in a way we might find counterinuitive: by burying it. Dating these underground hoardes is tricky, but it seems that Scandinavians buried most of them in the sixth century CE. These burials contributed to a gold shortage in Scandinavia that would endure for centuries.

The great oral traditions of Norse mythological poetry also date from the sixth century. Most people have heard of Ragnarök: the "twilight of the gods" that ends with the Earth incinerated and reborn. Fewer have come across the concept of Fimbulvetr, the "mighty winter" that heralds the final battle of the gods.

The Prose Edda, a thirteenth-century transcription of Norse mythology, describes Fimbulvetr in vivid detail. “Then snow will drift from all directions," the Edda predicts. "There will then be great frosts and keen winds. The sun will do no good. There will be three of these winters together and no summer between.” According to the Poetic Edda, a collection of poems also committed to writing in the thirteenth century, “The sun turns black . . . The bright stars vanish from the sky.”

These precise descriptions of an apocalyptic winter have no parallel in other religious texts or mythical traditions. Instead, they echo the sixth-century reports of Cassiodorus, Procopius, and other astonished observers of real environmental transformations. Scandinavians fleeing their homes amid catastrophic cooling may well have felt like they were living through a preview of the apocalypse.

The trauma caused by sixth-century environmental changes may therefore be imprinted on Norse mythology. Ideas of a new world in the wake of Ragnarök may also reflect the consequences of real events, such as the new settlements and cultures that emerged amid climatic cooling.

The Earth, consumed by fire in the wake of Ragnarök. Source: Emil Doepler, c. 1905. Walhall, die Götterwelt der Germanen. Martin Oldenbourg, Berlin.

Can these ancient calamities offer any lessons for our warmer future? Perhaps. They suggest, for example, that complex, densely populated societies, far from being insulated from the effects of climate change, may actually be most at risk. When populations brush up against the carrying capacity of agricultural land, sudden environmental shifts can be catastrophic. In these situations, societies already embroiled in resource-draining wars could be particularly vulnerable. The consequences of sixth-century cooling hint, also, that responses to even short-lived climatic upheavals can profoundly alter cultures in ways that endure for centuries, or even millennia.

Ancient societies, of course, have little similarity to our own. Yet their struggles in periods of dramatic climate change may still shed some light on our prospects in a warming world. To understand the future, we would be well served to look back at the distant past.

Sources:

Abbott, Dallas H., Dee Breger, Pierre E. Biscaye, John A. Barron, Robert A. Juhl, and Patrick McCafferty. "What caused terrestrial dust loading and climate downturns between AD 533 and 540?." Geological Society of America Special Papers 505 (2014): 421-438.

Arjava, Antti. "The mystery cloud of 536 CE in the Mediterranean sources." Dumbarton Oaks Papers 59 (2005): 73-94.

Axboe, Martin. "The year 536 and the Scandinavian gold hoards." Medieval Archaeology 43 (1999).

Gräslund, Bo, and Neil Price. "Twilight of the gods? The ‘dust veil event’ of AD 536 in critical perspective." Antiquity 86:332 (2012): 428-443.

Hamacher, Duane W. "Comet and meteorite traditions of Aboriginal Australians." Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures (2014): 1-4.

Widgren, Mats. "Climate and causation in the Swedish Iron Age: learning from the present to understand the past." Geografisk Tidsskrift-Danish Journal of Geography 112:2 (2012): 126-134.

43:T4481,

Dr. Tim Newfield, Princeton University, and Dr. Inga Labuhn, Lund University.

Carolingian mass grave, Entrains-sur-Nohain, INRAP.

Will climate change trigger widespread food shortages and result in huge excess mortality in our future? Many historians have argued that it has before. Anomalous weather, abrupt climate change, and extreme dearth often work together in articles and books on early medieval demography, economy and environment. Few historians of early medieval Europe would now doubt that severe winters, droughts and other weather extremes led to harvest failures and, through those failures, food shortages and mortality events.

Most remaining doubters adhere to the idea that food shortages had causes internal to medieval societies. Instead of extreme weather or abrupt climate change, they blame accidents of (population) growth, deficient agrarian technology, unequal socioeconomic relations and weak institutions. Yet only rarely they have stolen the show or dominated the scholarship. For example, Amartya Sen’s “entitlement approach” to subsistence crises, which assigns primary importance to internal processes, has made few inroads in the literature on early medieval dearth, although in later periods it has many adherents.

Of course, the idea that big events have a single cause – monocausality, in other words – rarely convinces historians for long. Famine theorists and historians of other eras and world regions now argue that neither external forces such as weather, nor internal forces such as entitlements, alone capture the complexity of food shortages. They propose that these two explanatory mechanisms, often labeled “exogenous” and “endogenous,” respectively, should not be considered independent of one another or mutually exclusive. To them, periods of dearth can be explained by environmental anomalies, like unusual and severe plant-damaging weather, that coincide with socioeconomic vulnerability and declining (for most people) entitlement to food.

These explanations are more convincing. It seems that diverse factors acted in concert to cause, prolong and worsen food shortages. But proof for complex explanations for dearth in the distant past is hard to come by. Though they can be misleading, simpler, linear explanations are much easier to pull out of the extant evidence. This is true even when the sources are plentiful, as they are, at least by early medieval standards, for some regions and decades of Carolingian Europe. Food shortages in the Carolingian period, especially those that occurred during the reign of Charlemagne, have attracted the attention of scholars since the 1960s.

Left: Bronze equestrian statuette of Charlemagne or possibly his grandson Charles the Bald (823-877). Discovered in Saint-Étienne de Metz and now in the Louvre. The figure is ninth century in date. The horse might be earlier and Byzantine. Charles the Bald ruled the western portion of the post-Verdun empire, although whether he was actually bald is still debated.
Right: A Carolingian denarius (812-814) depicting Charlemagne. The Charlemagne of the Charlemagne reliquary mask (Center) is handsomer. The coin, though, is contemporary and the bust is from the mid fourteenth century. Housed in the Aachener Dom’s treasury, it contains a skullcap thought to be that of the emperor.

For the Carolingian period, ordinances from the royal court, capitularies, reveal hoarding and speculation, and document official attempts to control the prices and movements of grain, while annalists and hagiographers recount severe winters and droughts. All of this evidence sheds light on dearth. Yet the legislative acts point to internal pressures on food supply, while the narrative sources highlight external ones. As we have seen, neither pressure adequately explains subsistence crises alone.

Unfortunately, however, we rarely have evidence for endogenous and exogenous factors at the same time. Around the year 800, when Leo III crowned Charlemagne imperator, most evidence for dearth comes from the capitularies. Before and after, narrative evidence dominates. So Charlemagne’s food shortages appear to have had internal drivers, and Charles the Bald’s external ones. Or so the written sources lead us to believe.

Carolingian Europe as of August 843 following the Treaty of Verdun. Under rex and imperator Charlemagne (742-814), Carolingian territory stretched to include the area of Europe outlined here.

Fortunately, evidence from other disciplines allows historians to fill in some of the gaps. External pressures are easier to establish by turning to the palaeoclimatic sciences. Using them, we are beginning to rewrite the history of continental European dearth, weather and climate from 750 to 950 CE. We are working on a new study that combines a near-exhaustive assessment of Carolingian written evidence for subsistence crises and weather with scientific evidence for changes in average temperature, precipitation, and volcanic activity (which can influence climate).

We are trying to answer some big questions, such as: What role did droughts, hard winters and extended periods of heavy rainfall have in sparking, prolonging or worsening Carolingian food shortages? Were these external forces the classic triggers of dearth that many early medievalists think they were?

Indicators of past climate embedded in trees and ice can test and corroborate observations of anomalous temperature and precipitation. For instance, the droughts of 794 and 874 CE, documented respectively in the Annales Mosellani and Annales Bertiniani, show up in the tree ring-based Old World Drought Atlas (OWDA, see below). Additionally, as McCormick, Dutton and Mayewski demonstrated, multiple severe Carolingian winters also align fairly neatly with atmosphere-clouding Northern Hemisphere volcanism reconstructed using the GISP2 Greenlandic ice core.

The Old World Drought Atlas (OWDA) for 794 and 874. Negative values indicate dry conditions, positive values indicate wet conditions (from Cook et al. 2015).

By marrying written and natural archives, we are able to perfect our appreciation of the scale and extent of the weather extremes that coincide with Carolingian periods of dearth. Yet instead of simply providing answers, our integrated data are raising questions, and pushing us towards a messier history of early medieval food shortage. This is because the independent lines of evidence often do not agree. For example, only two of the 15 driest years between 750 and 950 CE in the OWDA coincide with drought in Carolingian sources.

Admittedly, some of this dissonance may be artificial. The written record for weather and dearth is incomplete. To be sure, some places and times during the Carolingian era, broadly defined as it is here, are poorly documented. So reported drought years can appear kind of wet in the tree-based OWDA in some Carolingian regions (parts of northern Italy and Provence in 794 and 874 for instance).

Moreover, the detailed or “high-resolution” palaeoclimatology available now for early medieval Europe is much better for some regions than others. Tree-ring series extending back to 750 presently exist for few European regions. It is simply not possible to precisely pair some reported weather extremes or dearths to palaeoclimate reconstructions. Indeed, spatially the two lines of evidence can be mismatched. They can also be seasonally inconsistent, as the trees tell us far less about temperature and precipitation in the winter than they do for the summer.

Matches between historical and scientific evidence are therefore generally limited to the growing seasons, in places where written sources and palaeoclimate data overlap. That is enough to yield some surprising results. When the written record is densest, there is natural evidence for severe weather and rapid climate change, but not for food shortages.

Take the dramatic drop in average temperatures registered in European trees at the opening of the ninth century. According to the 2013 PAGES 2K Network European temperature reconstruction, temperatures were cooler around the time of Charlemagne’s coronation than they had been at any time between the mid sixth and early eleventh centuries. This dramatic cooling aligns well with a relatively small Northern Hemisphere volcanic eruption, detected in the recent ice-core record of volcanism led by Sigl. The eruption would have ejected sunlight-scattering sulfur aerosols into the atmosphere. Notably, larger events in the Carolingian era, like those of 750, 817 and 822, clearly had less of an influence on European temperature. The cold of 800 is equally pronounced but less unusual in a tree-based temperature reconstruction from the Alps. In this series, the late 820s are remarkably cooler.

Documentary sources register the falling temperatures. The Carolingian Annales regni francorum report severe growing-season frosts (aspera pruina) in 800. The Irish Annals of Ulster document a difficult and mortal winter in an entry quite possibly misdated in the Hennessy edition at 798 (799 or the 799/800 winter is more likely). Yet surprisingly, there is no contemporary record of food shortages in Europe.

Top: European Temperature Reconstruction, 0-2000 CE (data from Pages 2K Consortium, 2013).
Bottom: Middle Red: PAGES 2K 2013 Consortium European temperatures; Middle Burgundy: Büntgen et al 2011 Alpine temperature reconstruction; Top: Sigl et al 2015 ice-core record of Global Volcanic Forcing (GVF); Bottom: Written evidence for food shortages, both famines (F) and lesser shortages (LS). ‘W’ indicates no evidence for dearth but evidence for extreme weather. Between 750 and 950 we have identified 23 food shortages: 12 spatially and temporally circumscribed lesser shortages and 11 large multi-year famines.

Scholars tend to focus on instances when the written evidence for dearth and the natural evidence for anomalous weather align tidily. It seems that just as often, however, the two lines of evidence do not match so neatly. Severe weather may not always have triggered dearth in the early Middle Ages. Contemporary peoples could apparently cope with weather extremes in ways that allowed them to escape food shortages.

Early medieval vulnerability to external forces of dearth seems to have varied over space and time. We need to investigate the contrasting abilities of peoples from different early medieval regions and subperiods, participating in distinct agricultural economies with their own agrarian technologies, to withstand plant-damaging environmental extremes.

Several studies already suggest early medievals were capable of responding to gradual climate change. But to argue that they were not rigid or helpless when faced with marked seasonal temperature or precipitation anomalies, we must first identify, from sparse sources, potential moments of resilience. In this we run the risk of reading too much into absences of evidence. Yet the conclusion seems inescapable: when written sources are relatively abundant and there is no record of dearth during notable deviations in temperature and precipitation, early medievals must have adapted successfully.

Going forward, we must identify both moments and mechanisms of early medieval resilience in the face of climate change. Teasing these out from diverse sources might be tough going, but these elements are missing from the history of early medieval dearth and climate. Their omission has allowed for misleadingly neat histories of climate change and disaster in the period. Similar problems might well plague other histories that too clearly link climate changes to food shortages and mortality crises. Research that complicates these links could offer compelling new insights about our warmer future.

Authors' note: this is a short sampling of a much longer and more detailed multidisciplinary examination of Carolingian dearth, weather and climate, currently in preparation.

Select Reading:

P. Bonnassie, “Consommation d’aliments immondes et cannibalisme de survie dans l’Occident du Haut Moyen Âge” Annales: Économies, Sociétés, Civilisations 44 (1989), pp. 1035-1056.

U. Büntgen et al, “2,500 Years of European Climate Variability and Human Susceptibility” Science 331 (2011), pp. 578-582.

U. Büntgen and W. Tegel, “European Tree-Ring Data and the Medieval Climate Anomaly” PAGES News 19 (2011), pp. 14-15.

F. Cheyette, “The Disappearance of the Ancient Landscape and the Climatic Anomaly of the Early Middle Ages: A Question to be Pursued” Early Medieval Europe 16 (2008), pp. 127-165.

E. Cook et al, “Old World Megadroughts and Pluvials during the Common Era” Science Advances 1 (2015), e1500561.

S. Devereux, Theories of Famine (Harvester Wheatsheaf, 1993).

R. Doehaerd, Le Haut Moyen Âge occidental: Economies et sociétés (Nouvelle Clio, 1971).

P.E. Dutton, “Charlemagne’s Mustache” and “Thunder and Hail over the Carolingian Countryside” in his Charlemagne’s Mustache and Other Cultural Clusters of a Dark Age (Palgrave, 2004), pp. 3-42, 169-188.

M. McCormick, P.E. Dutton and P. Mayewski, “Volcanoes and the Climate Forcing of Carolingian Europe, A.D. 750-950” Speculum 82 (2007), pp. 865-895.

T. Newfield, “The Contours, Frequency and Causation of Subsistence Crises in Carolingian Europe (750-950)” in P. Benito i Monclús ed., Crisis alimentarias en la edad media: Modelos, explicaciones y representaciones (Editorial Milenio, 2013), pp. 117-172.

PAGES 2k Network, “Continental-Scale Temperature Variability during the Past Two Millennia” Nature Geoscience 6 (2013), pp. 339-346.

K. Pearson, “Nutrition and the Early Medieval Diet” Speculum 72 (1997), pp. 1-32.

A. Sen, Poverty and Entitlements: An Essay on Entitlement and Deprivation (Oxford University Press, 1981).

M. Sigl et al, “Timing and Climate Forcing of Volcanic Eruptions for the Past 2,500 Years” Nature 523 (2015), pp. 543-549.

P. Slavin, “Climate and Famines: A Historical Reassessment” WIREs Climate Change 7 (2016), pp. 433-447.

A. Verhulst, “Karolingische Agrarpolitik: Das Capitulare de Villis und die hungersnöte von 792/793 und 805/806” Zeitschrift fur Agrargeschichte und Agrarsoziologie 13 (1965), pp. 175-189.

44:T2ac8,

Dr. Bathsheba Demuth, Brown University.

The Greenlandic coast. Source: TheBrockenInaGlory, Wikimedia Commons, 2005, commons.wikimedia.org/wiki/File:Greenland_coast.JPG

In the year 1001 CE, Leif Erikson made landfall in Greenland, and traded with people who “in their purchases preferred red cloth; in exchange they had furs to give.” The Vikings called these people Skraelings. Present-day archeologists and historians call them the Thule. At its height, Thule civilization spread from its origins along the Bering Strait across the Canadian Arctic and into to Greenland. The ancestors of today’s Inuit and Inupiat, the Thule accomplished what Erikson and subsequent generations of Europeans never managed: living in the high Arctic without supplies of food, technology, and fuel from more temperate climates.

The Thule left archeological evidence of a technologically sophisticated, vigorous people. They invented the umiak, an open walrus-hide boat so large that it was sometimes equipped with a sail. These boats, when used alongside small, nimble kayaks, made the Thule formidable marine-mammal hunters. On land, they harnessed dogs to sleds and built homes half-underground, insulated by earth and beamed with whale bones.

People did inhabit the high North American Arctic before the Thule. Their immediate predecessors, called the Dorset by archeologists, were expert carvers, and there are signs of other cultures that date back at least five thousand years. But the Thule appear to have been a particularly robust society, one that inhabited thousands of challenging Arctic miles. Eventually, they even traded with Europeans for metal tools, sending walrus ivory as far abroad as Venice.

Thule migration routes from the Bering Strait east. Map credit: anthropology.uwaterloo.ca/ArcticArchStuff

In the twentieth century, many archeologists linked the success of the Thule to the climate. In this view, rapid Thule expansion coincided with the Medieval Warm Period in the years between 1000 and 1300. The Thule were expert whalers, especially of bowhead whales. This slow species makes for good prey. Their 100-ton bodies can be fifty percent fat by volume, giving people ample calories to eat and burn through long winters. With the slight increase in temperature during the Medieval Warm Period, the theory went, the range of the bowhead whale expanded across newly ice-free waters. Atlantic and Pacific bowhead populations eventually met in the Arctic Ocean north of Canada, offering an uninterrupted banquet of blubber to hunters.

The Thule, in this view, were simply whale hunters who followed the migration of their prey in a warming climate. Environmental conditions, not a sophisticated culture, was the key explanation for their success. Emphasizing climate as the cause of migration and social success reduced the achievements of the Thule, essentially, to those of their prey.

However, twenty-first century evidence is changing this account of Thule migration. In 2000, Robert McGhee questioned the validity of the radiocarbon dates that helped establish Thule expansion as an eleventh-century phenomenon. He proposed the 1200s as the earliest date of migration. Then, genetic tests by marine biologists showed that Atlantic and Pacific bowhead whales did not mix their populations during the Medieval Warm Period, meaning that there was a substantial gap in whaling possibilities on the Arctic coast.

Something more complicated than just following the blubber drove the Thule eastward. McGhee speculated that communities moved for iron, which is short supply in the Arctic. Thule hunters learned from the Dorset people of a deposit left by the Cape York meteorite. They colonized huge territories to secure their access to this precious resource from outer space. Other specialists theorized that population pressure, overhunting, or warfare led the Thule to migrate east.

Thule archeological site, with whalebone beams among flooring stones. Photo credit: anthropology.uwaterloo.ca/ArcticArchStuf

The ongoing work of Canadian archeologists T. Max Friesen and Charles D. Arnold seems to confirm that we must look beyond simple climatic explanations for the Thule expansion. Working on Beaufort Sea and Amundsen Gulf sites, the pair established that there was no definitive Thule occupation in this part of the western Arctic prior to the thirteenth century. Because any Thule migrants would have had to pass through these points as they moved east, their research indicates that the Thule civilization was only beginning its continental spread around the year 1200, well into the period of warming. The climate may have helped the Thule quickly spread toward Greenland, but the onset of the Medieval Warm Period did not automatically draw people eastward.

Moreover, the work of other archeologists on the Melville Peninsula, along Baffin Bay, indicates that the Mediaeval Warm Period was not always so warm. Some areas of the Arctic saw slight temperature increases, but in general the millennium was cooler than those past. In places, the effects of the so-called Little Ice Age began a century or two before they were evident across the globe, meaning the Thule adapted not to a warmer Arctic, but a colder one. This cooling was more apparent in the west, where the team found fewer Thule sites but also more stability, both in the climate and the record of human occupation. To the east of the Melville Peninsula, where temperatures did warm, the climate was also more variable – adding a new set of complexities to social and economic life. The move into the central Arctic, therefore, reflected forces other than climate.

Beginning in the fifteenth century, Thule culture fragmented, specialized, and emerged eventually as distinct contemporary Inuit and Inupiat groups. The Little Ice Age is often the reason given for the disintegration of Thule civilization in the fifteenth century. Yet, the work by Finkelstein, Ross, and Adams indicates that, while the Thule abandoned some sites due to cooling trends, this did not hold in all cases. Other causes, including increased contact with Europeans and their infectious diseases, might have had more to do with the disintegration in some locations.

Overall, the new vision of the Thule prominence in the Arctic makes their rise shorter, but even more impressive. And if the Thule began their migration only in 1200, it seems unlikely they spread east simply to find iron. This would have required only smaller-scale movements to precise locations. Instead, the Thule developed a thriving, intricate network of settlements across the Arctic. For Friesen and Arnold, this is evidence that the Thule expanded in order to recreate the ideological and economic lives that they had enjoyed in their origins along the Bering Strait. And in just a century they did, not only by inhabiting land from the Bering Strait to Greenland, but through explorations to the northern edges of the continent.

All of this also helps us reinterpret a well-known tale from the Viking exploration of the Arctic. When Leif Erikson’s sister Freydis frightened off a band of Skraelingar in the early eleventh century by striking “her breast with the naked sword” of a fallen Viking, she was likely not fighting the Thule, as scholars have assumed. Perhaps it was the Dorset people that “were frightened, and rushed off in their boats.” The Thule, at least, were likely still a century away from the eastern Canadian coastline. They were not easily daunted either by a shifting climate or by Viking weapons.

References

Quotes from the Saga of Erik the Red, English translation by J. Sephton, can be found here: http://www.sagadb.org/eiriks_saga_rauda.en

Friesen, T. Max and Charles D. Arnold. “The Timing of the Thule Migration: New Dates from the Western Canadian Arctic,” American Antiquity 73 (2008): 527-538.

Finkelstein, S.A., J.M Ross, and J.K Adams. “Spatiotemporal Variability in Arctic Climates of the Past Millennium: Implications for the Study of Thule Culture on Melville Peninsula, Nunavut,” Arctic Antarctic, and Apline Research 41 (200): 442-454.

McGhee, Robert. “Radio Carbon Dating and the Timing of the Thule Migration,” in Appelit, M. Berglund, J, and Gullov, H.C. eds. Identities and Cultural Contacts in The Arctic: Proceedings from a Conference at the Danish National Museum. Copenhagen (2000): 181-191.

Morrison, David. “The Earliest Thule Migration.” Canadian Journal of Archaeology 22( 1999): 139-156.

Betts, Matthew, and T. Max Friesen, “Quantifying Hunter-Gatherer Intensification: A Zooarchaeological Case Study form Arctic Canada,” Journal of Anthropological Archaeology 23 (2004): 357-384.

Dyke, Arthur S., James Hooper, and James M. Savelle. “A History of Sea Ice in the Canadian Arctic Archipelago based on Postglacial Remains of the Bowhead Whale (Balaena mysticetus)”, Arctic 49 (1996): 235-255.

Park, Robert W. “The Dorset-Thule Succession Revisited,” in Appelit, M. Berglund, J, and Gullov, H.C. eds. Identities and Cultural Contacts in the Arctic: Proceedings from a Conference at the Danish National Museum. Copenhagen (2000): 192-205.

45:T1f19,

Dr. Gabriel Henderson, Aarhus University

A sunspot on the churning surface of the sun. Source: NASA.

Counting in everyday life is a relatively straightforward affair; one, two, three, and on and on. Less simple is the process of reliably counting the number of sunspots on the surface of the sun. Sunspots are darkened areas on the solar surface. In Europe, people knew of their existence at least since the early 17th century, and some of the larger sunspots were probably noted long before Galileo. Elsewhere, sunspot counts were maintained for much longer. Counting these darkened areas is one of the most effective ways to establish a record of the evolution in solar behavior. Not only do sunspot observations provide crucial information about changes in the sun’s magnetic field, they strongly correlate with long-term fluctuations in the amount of energy released by the sun – the so-called solar cycle.

Yet, in the 1970s, counting sunspots signified something much more dramatic and nefarious about the history of science itself. In these years, John “Jack” Eddy, an astrophysicist with the National Center for Atmospheric Research, began to scour old, dusty books in library basements to resuscitate a long-forgotten event in the history of solar behavior, behavior that seemed completely at odds with the prevailing orthodox understanding of the sun. Despite what appeared to be the historic and predictable vacillation in the number of sunspots every eleven years, a regularity known to exist since the mid-19th century, Eddy noticed in his records what appeared to be the virtual absence of sunspots between 1645 and 1715.

This curious blemish in the solar record was no small discovery. “If it really happened,” Eddy noted in one of his earliest talks on the matter, “we should recognize it as perhaps the most drastic thing that has ever happened to the sun since we began observing it and start including it in our work on the solar cycle." (Eddy, 1974) The implication was obvious: if the sun acted regularly and predictably every eleven years or so, how does one explain the disappearance of sunspots for almost a century?

The Maunder Minimum and the Dalton Minimum, another low in sunspot activity named after a nineteenth-century astronomer. Source: Robert A. Rohde, Global Warming Art project.

The lack of sunspots was not Eddy’s discovery, at least not in the purest sense. What he called the Maunder Minimum had been observed almost a century earlier by British astronomer Edward Walter Maunder, who began to publish his findings during the 1890s. To Eddy’s consternation, however, Maunder’s discovery appeared to have been forgotten by the astrophysics community. How could this be? Scientific observations and facts don’t just disappear, do they? To Eddy, the answer was yes. A cursory glance at the matter yielded at least one possible reason why: Maunder was not vocal enough about his discovery. But further research yielded a much richer narrative, one that compelled Eddy to examine the deeply held assumptions of his own profession.

Eddy’s investigation, as it turned out, showed that Maunder was not forgotten merely because of his inability to properly disseminate his finding about sunspots, but rather because the astrophysical community had – for almost a century – allowed their preexisting assumptions to blind them to new ideas. A conspiracy had taken place, Eddy argued, one based in what appeared to be a universal belief that the sun acted regularly and predictably according to the solar cycle – what he called the principle of solar uniformitarianism.

The strength of Maunder’s observations was insufficient to break the universally-accepted canon of solar regularity. Instead of acknowledging and understanding an anomaly in solar behavior, “solar physicists have largely continued to ignore or forget the anomaly, if real,” Eddy insisted in the spring of 1976. “Some have institutionalized the solar cycle and made a profession of extending it into the past and predicting in the future; ignoring, doubting, or intentionally diluting the claims of Maunder of this skeleton in the closet of solar physics." (Eddy, 1976)

John A. Eddy. Source: Barbara Eddy via Wikimedia Commons.

This was a dramatic claim, but one that became inextricably interwoven with Eddy’s public admonishment – if not condemnation – of professional orthodoxy within science itself. Eddy wrote about the topic, gave interviews, and addressed scientific and popular audiences – all in the hope that his tempest of activity would lead to Maunder’s long-overdue recognition. But perhaps more poignantly, Eddy portrayed himself as the detective who pulled back the curtain to reveal the biases and prejudices that prevented what he considered to be genuine scientific progress. For him, contemporary astrophysics was a stale and unstable artifice, and only through the work of pioneers like himself – and the forgotten Maunder – could one dispel the fashionable tropes that dictated popular understanding of scientific progress. As he described to an audience within the Boston Museum of Science in May 1978, “In fact, much of what we know, or think we know is not that way at all. And if we have the heart and stomach to look down at it closely, is based upon a shaky and often overextended framework of assumptions – cantilevered scaffolds of bamboo poles and weathered twine.” (Eddy, 1978)

This is an important story in part because it helps to explain why Eddy spoke about sunspots with what historian Kark Hufbauer referred to as “a missionary’s zeal.” (Hufbauer, 1991) But what else does the story show? It certainly does not mean that Eddy’s pioneering work led to a wholesale abandonment of the idea that the sun (for the most part) behaves in a regular, cyclical fashion. That interpretation would be too extreme. However, it would not be too extreme to argue that he used what he considered a crime against Maunder to justify his own predilections as a scientist. Throughout his professional life, he harbored a deep skepticism toward what he saw as scientists’ proclivity for unoriginality and challenged others’ apparent unwillingness to probe the very depths of their own professional, and sometimes erroneous, assumptions. Eddy was comfortable opening the closet.

~Gabriel Henderson

Sources:

Eddy, John, "The Long Solar Winter," 1974 December 5, Box 2, John Eddy Papers, National Center for Atmospheric Research.

Eddy, John, ”Maunder Minimum,” 15 April 1976, Box 3, JEP

Eddy, John, ”The Changing Sun,” 28 May 1978, Box 3, JEP

Hufbauer, Karl. Exploring the Sun: Solar Science Since Galileo. Baltimore: Johns Hopkins University Press, 1991.

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It's Maunder Minimum Month at HistoricalClimatology.com. This is our first of two feature articles on the Maunder Minimum. The second, by Gabriel Henderson of Aarhus University, will examine how astronomer John Eddy developed and defended the concept.

The 11-year solar cycle, imaged by NASA's SOHO spacecraft in extreme ultraviolet light. Source: NASA.

Although it may seem like the sun is one of the few constants in Earth’s climate system, it is not. Our star undergoes both an 11-year cycle of waning and waxing activity, and a much longer seesaw in which “grand solar minima” give way to “grand solar maxima.” During the minima, which set in approximately once per century, solar radiation declines, sunspots vanish, and solar flares are rare. During the maxima, by contrast, the sun crackles with energy, and sunspots riddle its surface.

The most famous grand solar minimum of all is undoubtedly the Maunder Minimum, which endured from approximately 1645 until 1720. It was named after Edward Maunder, a nineteenth-century astronomer who painstakingly reconstructed European sunspot observations. The Maunder Minimum has become synonymous with the Little Ice Age, a period of climatic cooling that, according to some definitions, endured from around 1300 to 1850, but reached its chilliest point in the seventeenth century.

During the Maunder Minimum, temperatures across the Northern Hemisphere declined, relative to twentieth-century averages, by about one degree Celsius. That may not sound like much – especially in a year that is, globally, still more than one degree Celsius hotter than those same averages – but consider: seventeenth-century cooling was sufficient to contribute to a global crisis that destabilized one society after another. As growing seasons shortened, food shortages spread, economies unraveled, and rebellions and revolutions were quick to follow. Cooling was not always the primary cause for contemporary disasters, but it often played an important role in exacerbating them.

Life on the ice in Amsterdam, during a typically frigid winter in the Maunder Minimum. Source: Jan Abrahamsz. Beerstraten, "Het Paalhuis en de Nieuwe Brug te Amsterdam in de Winter," 1640-1666.

Many people – scholars and journalists included – have therefore assumed that any fall in solar activity must lead to chillier temperatures. When solar modelling recently predicted that a grand solar minimum would set in soon, some took it as evidence of an impending reversal of global warming. I even received an email from a heating appliance company that encouraged me to hawk their products on this website, so our readers could prepare for the cooler climate to come! Of course, the warming influence of anthropogenic greenhouse gases will overwhelm any cooling brought about by declining solar activity.

In fact, scientists still dispute the extent to which grand solar minima or maxima actually triggered past climate changes. What seems certain is that especially warm and cool periods in the past overlapped with more than just variations in solar activity. Granted, many of the coldest decades of the Little Ice Age coincided with periods of reduced solar activity: the Spörer Minimum, from around 1450 to 1530; the Maunder Minimum, from 1645 to 1720; and the Dalton Minimum, from 1790 to 1820. However, one of the chilliest periods of all – the Grindelwald Fluctuation, from 1560 to 1630 – actually unfolded during a modest rise in solar activity. Volcanic eruptions, it seems, also played an important role in bringing about cooler decades, as did the natural internal variability of the climate system. Both the absence of eruptions and a grand solar maximum likely set the stage for the Medieval Warm Period, which is now more commonly called the Medieval Climate Anomaly.

This gets to the heart of what we actually mean when we use a term like “Maunder Minimum” to refer to a period in Earth’s climate history. Are we talking about a period of low solar activity? Or are we referring to an especially cold climatic regime? Or are we talking about chilly temperatures and the changes in atmospheric circulation that cooling set in motion? In other words: what do we really mean when we say that the Maunder Minimum endured from 1645 to 1720? How does our choice of dates affect our understanding of relationships between climate change and human history in this period?

To find an answer to these questions, we can start by considering the North Sea region. This area has yielded some of the best documentary sources for climate reconstructions. They allow environmental historians like me to dig into exactly the kinds of weather that grew more common with the onset of the Maunder Minimum. In Dutch documentary evidence, for example, we see a noticeable cooling trend in average seasonal temperatures that begins around 1645. On the surface of things, it seems like declining solar activity and climate change are very strongly correlated.

And yet, other weather patterns seem to change later, one or two decades after the onset of regional cooling. Weather variability from year to year, for example, becomes much more pronounced after around 1660, and that erraticism is often associated with the Maunder Minimum. Severe storms were more frequent only by the 1650s or perhaps the 1660s, and again, such storms are also linked to the Maunder Minimum climate. In the autumn, winter, and spring, easterly winds – a consequence, perhaps, of a switch in the setting of the North Atlantic Oscillation – increased at the expense of westerly winds in the 1660s, not twenty years earlier.

A depiction of William III boarding his flagship prior to the Glorious Revolution of 1688. Persistent easterly, "Protestant" winds brought William's fleet quickly across the Channel, and thereby made possible the Dutch invasion of England. For more, read my forthcoming book, "The Frigid Golden Age." Source: Ludolf Bakhuizen, "Het oorlogsschip 'Brielle' op de Maas voor Rotterdam," 1688.

All of these weather conditions mattered profoundly for the inhabitants of England and the Dutch Republic: maritime societies that depended on waterborne transportation. Rising weather variability made it harder for farmers to adapt to changing climates, but often made it more profitable for Dutch merchants to trade grain. More frequent storms sank all manner of vessels but sometimes quickened journeys, too. Easterly winds gave advantages to Dutch fleets sailing into battle from the Dutch coast, but westerly winds benefitted English armadas. If we define the Maunder Minimum as a climatic regime, not (just) a period of reduced sunspots, and if we care about its human consequences, what should we conclude? Did the Maunder Minimum reach the North Sea region in 1645, or 1660?

These problems grow deeper when we turn to the rest of the world. Across much of North America, temperature fluctuations in the seventeenth century did not closely mirror those in Europe. There was considerable diversity from one North American region to another. Tree ring data suggests that northern Canada appears to have experienced the cooling of the Maunder Minimum. Western North America also seems to have been relatively chilly in the seventeenth century, although there chillier temperatures probably did not set in during the 1640s.

By contrast, cooling was moderate or even non-existent across the northeastern United States. Chesapeake Bay, for instance, was warm for most of the seventeenth century, and only cooled in the eighteenth century. Glaciers advanced in the Canadian Rockies not in the seventeenth century, but rather during the early eighteenth century. Their expansion was likely caused by an increase in regional precipitation, not a decrease in average temperatures.

Still, the seventeenth century was overall chillier in North America than the preceding or subsequent centuries, and landmark cold seasons affected both shores of the Atlantic. The consequences of such frigid weather could be devastating. The first settlers to Jamestown, Virginia had the misfortune of arriving during some of the chilliest and driest weather of the Little Ice Age in that region. Crop failures contributed to the dreadful mortality rates endured by the colonists, and to the brief abandonment of their settlement in 1610.

An early seventeenth-century map of New France. Just look at all those trees! Source: Samuel de Champlain, "Map of New France," 1612.

Moreover, many parts of North America do seem to have warmed in the wake of the Maunder Minimum, in the eighteenth century. This too could have profound consequences. In the seventeenth century, settlers to New France had been surprised to discover that their new colony was far colder than Europe at similar latitudes. They concluded that its heavy forest cover was to blame, and with good reason: forests do create cooler, cloudier microclimates. Just as the deforestation of New France started transforming, on a huge scale, the landscape of present-day Quebec, the Maunder Minimum ended. Settlers in New France concluded that they had civilized the climate of their colony, and they used this as part of their attempts to justify their dispossession of indigenous communities.

Despite eighteenth-century warming in parts of North America, the dates we assign to the Maunder Minimum do look increasingly problematic when we look beyond Europe. If we turn to China, we encounter a similar story. Much of China was actually bitterly cold in the 1630s and early 1640s, before the onset of the Maunder Minimum elsewhere. This, too, had important consequences for Chinese history. Cold weather and precipitation extremes ruined crops on a vast scale, contributing to crushing famines that caused particular distress in overpopulated regions. The ruling Ming Dynasty seemed to have lost the “mandate of heaven,” the divine sanction that, according to Confucian doctrine, kept the weather in check. Deeply corrupt, riven by factional politics, undermined by an obsolete examination system for aspiring bureaucrats, and scornful of martial culture, the regime could adequately address neither widespread starvation, nor the banditry it encouraged.

Climatic cooling caused even more severe deprivations in neighboring, militaristic Manchuria. There, the solution was clear: to invade China and plunder its wealth. The first Manchurian raid broke through the Great Wall in 1629, a warm year in other parts of the Northern Hemisphere. Ultimately, the Manchus capitalized on the struggle between Ming and bandit armies by seizing China and founding the Qing (or "Pure") Dynasty in 1644.

China under the Ming Dynasty was arguably the most powerful empire of its time. Even as it unravelled in the early seventeenth century, its cultural achievements were impressive, as this painting of fog makes clear. Source: Anonymous, "Peach Festival of the Queen Mother of the West," early 17th century.

This entire history of cooling and crisis predates the accepted starting date of the Maunder Minimum. Yet, the fall of the Ming Dynasty unfolded in one relatively small part of present-day China. Average temperatures in that region reached their lowest point in the 1640s. By contrast, average temperatures in the Northeast warmed by the middle of the seventeenth century. Average temperatures in the Northwest also warmed slightly during the mid-seventeenth century, and then cooled during the late Maunder Minimum.

Smoothed graphs that show fluctuations in average temperature across centuries or millennia give the impression that dating decade-scale warm or cold climatic regimes is an easy matter. Actually, attempts to precisely date the beginning and end of just about any recent climatic regime are sure to set off controversy. This is not only because global climate changes have different manifestations from region to region, but also because climate changes, as we have seen, involve much more than shifts in average annual temperature. Did the Maunder Minimum reach northern Europe, for instance, when average annual temperatures declined, when storminess increased, when annual precipitation rose or fell, or when weather became less predictable?

Historians such as Wolfgang Behringer have argued that, when dating climatic regimes, we should also consider the “subjective factor” of human reactions to weather. For historians, it makes little sense to date historical periods according to wholly natural developments that had little impact on human beings. Maybe historians of the Maunder Minimum should consider not when temperatures started declining, but rather when that decline was, for the first time, deep enough to trigger weather that profoundly altered human lives. When we consider climate changes in this way, we may be more inclined to subjectively date climatic regimes using extreme events, such as especially cold years, or particularly catastrophic storms. Dating climate changes with an eye to human consequences does take historians away from the statistical methods and conclusions pioneered by scientists, but it also draws them closer to the subjects of historical research.

In my work, I do my best to combine all of these definitions, and incorporate many of these complexities. I date climatic regimes by considering their cause – solar, volcanic, or perhaps human – and by working with statisticians who can tell me when a trend becomes significant. However, I also try to consider the many different kinds of weather associated with a climatic shift, and the consequences that extremes in such weather could have for human beings.

As you might expect, this is not always easy. I have long held that the Maunder Minimum, in the North Sea region, began around 1660. Increasingly, I find it easier to begin with the broadly accepted date of 1645, but distinguish between different phases of the Maunder Minimum. An earlier phase marked by cooling might have started in 1645, but a later phase marked by much more than cooling took hold around 1660.

These are messy issues that yield messy answers. Yet we must think deeply about these problems. Not only can such thinking affect how we make sense of the deep past, but it can also provide new perspectives on modern climate change. When did our current climate of anthropogenic warming really start? At what point did it start influencing human history, and where? What can that tell us about our future? These questions can yield insights on everything from the contribution of climate change to present-day conflicts, to the timing of our transition to a thoroughly unprecedented global climate, to the urgency of mitigating greenhouse gas emissions.

~Dagomar Degroot

Further Reading:

Behringer, Wolfgang. A Cultural History of Climate. Cambridge: Polity Press, 2010.

Brooke, John. Climate Change and the Course of Global History: A Rough Journey. Cambridge: Cambridge University Press, 2014.

Coates, Colin and Dagomar Degroot, “‘Les bois engendrent les frimas et les gelées:’ comprendre le climat en Nouvelle-France." Revue d'histoire de l'Amérique française 68:3-4 (2015): 197-219.

Dagomar Degroot, “‘Never such weather known in these seas:’ Climatic Fluctuations and the Anglo-Dutch Wars of the Seventeenth Century, 1652–1674.” Environment and History 20.2 (May 2014): 239-273.

Eddy, John A. “The Maunder Minimum.” Science 192:4245 (1976): 1189-1202.

Parker, Geoffrey. Global Crisis: War, Climate Change and Catastrophe in the Seventeenth Century. London: Yale University Press, 2013.

White, Sam. “Unpuzzling American Climate: New World Experience and the Foundations of a New Science.” Isis 106:3 (2015): 544-566.

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Dr. Alan MacEachern, University of Western Ontario.

Western's Archives and Research Collections Centre (ARCC) storage room. Photo by Gabrielle Bossy.

In 2008, I had a meeting at the Environment Canada headquarters in Downsview, Ontario, and afterward staff gave me a tour. Since I’m a historian, they showed me the old stuff. Down in the basement – not quite the warehouse scene at the end of Raiders of the Lost Ark, but close enough – they led me along row after row of weather observations: all of the original paper forms and registers that since 1840 had been filled out by what would eventually be thousands of observers at thousands of weather stations across Canada. Environment Canada had long ago squeezed the quantitative data they wanted from the observations, and from it created an online National Climate Data and Information Archive. That may have actually put the physical collection more at risk; a teary librarian told of worrying she would return from vacation someday and find it had been thrown out. Staff were maintaining the collection as best they could, but they knew the facility was not up to archival standards – a massive steam pipe loomed menacingly nearby – and they were concerned about the lack of a long-term plan for it. The collection should rightly have gone to Library and Archives Canada (LAC), but in earlier decades the archives had expressed no interest in it and more recently had experienced an acquisitions freeze.

So without any real plan, let alone authorization, I offered to take the collection off Environment Canada’s hands.

Environment Canada weather stations, 1840-1960. Visualization by Josh MacFadyen, Arizona State University.

At the time, I was a dyed-in-the-wool environmental historian increasingly feeling that I had somehow neglected the most pressing environmental issue of our time, climate change. Helping protect a nationally-significant climate history collection seemed like good karma.

I went straight from Environment Canada to my university archives. Thankfully, a few years earlier the archives had moved into a new building containing a high density module capable of holding one million volumes. Thankfully, too, University Archivist Robin Keirstead was excited by the idea of having the collection come to Western University, so it could be better preserved, more accessible to researchers, and made available for teaching purposes. Robin and I formally contacted Environment Canada and LAC, expressing Western’s interest in receiving the collection.

It took years of negotiation, but what ultimately made the transfer happen was that some folks at Environment Canada thought these old records were priceless and others thought they were worthless, so both concluded it would be great if they were at Western.

In 2014, the collection arrived at Western on long-term loan – here is a full listing of it. There are several hundred volumes of correspondence, letterbooks, and journals related to Canadian meteorological and climatological history between 1828 and 1967. But the real jewels of the collection are the almost 900 archival boxes (an estimated 1.6 million pages) containing all of Environment Canada’s extant daily weather observations between 1840 and 1960. From what we could determine, this was the largest archival arrangement ever made between a Canadian university and the federal government.

Mission accomplished. …But now what?

“Super salubrious.” Howard D. Sloat, Jarvis, Ontario, August 1954, EC151, Environment Canada collection.

This was already a good news story as far as I was concerned, because the Environment Canada collection will be protected at archival standards indefinitely (presumably, until LAC is in a position to take it). But now that it was at my university, I wanted to see it used. I advertised its availability to researchers across Canada. I developed a climate history course that utilized it. And I considered what contributions neophyte climate history researchers – like my students, like me – could make with it.

To begin, we are focusing on the qualitative remarks that observers included alongside their quantitative data. Although Environment Canada long encouraged (or, in some eras, tolerated) observers’ remarks on such matters as extreme weather, farming conditions, and changing seasons, it had never figured out a way to utilize these remarks, including in its climate archive. This qualitative data remained untapped.

Students and I are working to change that. In the past year, we have begun creating a database of remarks from the collection. We are transcribing everything the observers thought worth observing (with the important exception that we are ignoring the hundreds of thousands of entries such as “Clear,” “Fair,” or “Rain”). There are many entries on crop conditions and the status of harvests, on smoke from forest fires, on Northern lights, on matters of local political or social interest. There are also many entries that offer insights into the history of the meteorological service itself.

“Hard maple in blossom. Oriole return. Swallows return. English Cherry blossom. Canaries return. Ice 3/16 inches ground. Orchards in blossom. Forest well leaved out. Fire flies seen. Crops all look well except corn it is yellow with the cold and wet.” Malcolm McDonald, Lucknow, Ontario, May 1902, EC172, Environment Canada collection.

But of special interest – both to the observers and to us – is phenological information. Phenology is the study of cyclical natural phenomena, and weather observers documented, often over the course of decades, the dates of ice break-up and freeze-up on rivers and lakes, when the first of various bird species appeared, when wildflowers bloomed, when spring peepers emerged. The observers were especially vigilant during what might be called the “phenological moment” of the late 19th and early 20th century, when Canadian individuals and learned societies became intent in gathering such information as a means of gaining biological and meteorological knowledge about their nation. With historians and climate scientists today seeking to verify older meteorological observations and to understand other ways of knowing climate, these observations assume new significance.

The database that Western History students and I are creating already has tens of thousands of tagged entries. In the near future, we will shift to the creation of a website that allows for geographical, temporal, and thematic searching of these observations, at micro- to macro- scales. Interested in Ajax, Ontario or in all of Canada? In your birthday or in a fifty-year timespan? In reports on earthquakes, orioles, or lilacs, or on all extreme weather, all fauna, all flora? We certainly hope to use this for research purposes, but our project’s ultimate goal is to make these observations available to climate researchers, and to the public, so that they make findings of their own. More good karma – climate research requires it.

Contact me at amaceach@uwo.ca if you have questions about the Environment Canada collection or research access to it.

~Alan MacEachern

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Dr. Tim Newfield, Princeton University.

The sun, dimmed by fog. Source: 0xefbeadde.wordpress.com

The June 1991 Pinatubo eruption in the Philippines was one of the largest volcanic eruptions of the twentieth century. It is well documented. There are living witnesses, newspaper articles, detailed surveys of the mountain before and after it blew its top, and satellite maps of the ejecta. The eruption was photographed from the ground and the air, and today you can even YouTube it.

Pinatubo released up to 20 megatons of sulphur dioxide as many as 35 kilometers into the sky. It turned into fine sulphuric acid aerosol, and, within weeks, enveloped much of the Earth. The aerosols were suspended in the atmosphere for around two years. While there, they "veiled" the sun by absorbing or "backscattering" solar radiation. That heated the stratosphere but cooled Earth's surface. The volcano caused a sudden (but non-uniform) fall in average global temperatures of at least .5 degrees Celsius that was still in effect as late as late 1992. In the Northern Hemisphere, temperatures in summer 1992 fell by about 2 degrees Celsius.

Pinatubo on 12 June 1991, a few days before the big eruption. The mountain shrunk 300 meters in the 15 June explosion. Lonely Planet’s Philippines describes a hike up the mountain as ‘most accessible’, but warns not to attempt it in ‘dodgy weather’. Source: USGS.

Earlier and much larger volcanic eruptions in the late Holocene are more obscure. Take Tambora, which erupted in April 1815 and pumped 60 to 110 megatons of sulphur dioxide into the air, leading to one of the most infamous ‘Years Without a Summer’. No volcanologist or climate scientist doubts it dwarfed Pinatubo, but far less is known about the earlier eruption. There are fewer firsthand accounts, and no films or photos (though some argue Joseph Turner and other artists captured its far-reaching atmospheric effects). While the available instrumental data are useful, they are limited and local. Nevertheless, scientists have determined that it was one of the biggest volcanic episodes of the last several thousand years. A recent study estimated that it resulted, in some regions, in 2 to 4 degrees Celsius of cooling from June to August, 1816.

There were other large events, deeper in the historical past. Yet these episodes are far more mysterious. Often the culpable volcano (or volcanoes) is not known, and firsthand accounts (if any) are more than vague: they are cryptic.

For example, something traumatic appears to have affected the world in around the year 536 CE. The five reports that survive for this "536 event" say nothing of an eruption. They merely describe in vague terms a sort of unusual sun dimming or atmospheric veiling. The Roman statesman Cassiodorus, for example, describes a dim moon, and a sun that lost its "wonted light" and appeared "bluish," as if in "transitory eclipse throughout the whole year."

These reports leave room to doubt that the phenomenon they describe was really volcanic in origin. Their mysteriousness, however, has spurred intense interest from scholars and enthusiasts since the phenomenon first appeared in the pages of the Journal of Geophysical Research, in 1983. NASA geoscientists Richard Stothers and Michael Rampino discovered a stratosphere-clouding volcanic episode tucked away in four (but, by 1988, five) late antique texts. They also found it in sulphate in Greenlandic ice, and they discovered pumice-lodged wood they date to 540 ±90 CE (meaning give or take 90 years), on Rabaul, a volcano in Papua New Guinea.

Since 1983, much has changed. Rabaul is long gone. Even before it seemed the dust veil witnessed (inconsistently) over the Mediterranean was not a volcanic dust veil, but instead some sort of "damp fog," the mountain was considered an unlikely source. In the 1980s, assessments of Antarctic ice did not turn up major mid sixth-century volcanism, but rather a signal from about 505 CE. That exonerated all Southern Hemispheric volcanoes from causing the 536 event. Rabual’s eruption chronology was re-dated with greater precision at least twice within eleven years, and it was determined that the 540±90 date was, in fact, an uncalibrated mix-up of the ages originally returned for the pumiceous wood. Rabaul actually exploded sometime in the interval of 633-670 CE, or (as of 2015) 667-699 CE.

Other volcanoes got their share of attention too. Before Rabaul, the Greenlandic sulphates were associated with the great ‘White River Ash’ eruption of Alaska’s Mount Churchill, which was dated roughly in 1975 to 700 ±100 CE, but in 2014 to 833-850 CE. They were also loosely associated with Iceland’s Eldgjá, which is well-known for erupting in the 930s. After, they were tied to the Chiapanecan El Chichón, Indonesia’s infamous Krakatoa, the now-dormant stratovolcano Haruna, and the El Savadorian Ilopango. The latter received considerable press in 2010, when palaeoecologist Robert Dull asserted its ‘paroxysmal’ Tierra Blanca Joven event, considered the largest Central American eruption of the last 84,000 years, and previously given third- and fifth- century dates, actually caused global cooling in 536 CE.

El Salvador’s largest and deepest (crater) lake, Lago de Ilopango. A survey of archaeological excavations suggested a 100-kilometre radius around the site was little- or un-inhabitable for a century after the eruption (whether that happened in 535/536 CE or not). A recent edition of Frommer’s Central America describes a visit to the (always) warm-water caldera as "overrated." Lago de Coatepeque, another volcanic lake 50 kilometres to west, is preferable. Source: NASA Earth Observatory

Yet for a while after 1983, scientists could find no eruptions in 536 CE. The original ice dates of 540 ±10 and c. 535 CE that Stothers and Rampino used to explain the abnormal Byzantine veiling were adjusted in 1984, at around the same time that Stother’s second, more influential article on a volcanic 536 event appeared in Science. This does not now seem surprising. The dates that scientists have given for most first-millennium eruptions have shifted back or forward in time at some point or another. Analyses of the remnants of eruptions in eruption-site sediments often produce ages that disagree by a half century or more. Studies of sulphate layers in ice cores also vary: a couple years in some cases, a decade or five in others.

For more than a decade after 1983, it seemed that the 536 event had other causes. Explanations were diverse. Some held that the clouding Procopius and his peers had witnessed was tropospheric and regional, not a stratospheric phenomenon of hemispheric or global proportions. Volcanism that was local and remarkable, but globally inconsequential, was the cause of some kind of low-hanging ‘damp fog’.

Others held firm: volcano or no volcano, the event was global. Oceanic outgassing, an interstellar cloud, and an asteroid or comet impact event were proposed. The latter, advanced in the early ‘90s, was not immediately popular. Some scholars considered an impactor a "much less likely" explanation for the 536 event than a major volcanic eruption, despite the then-complete lack of evidence for such an eruption. Yet the impact theory eventually gained some credibility. Different types of rocks and impacts were envisioned. A comet might have "air-bursted"’ in the upper atmosphere and ignited one or more vast forest fires, or alternatively a "medium-sized asteroid" struck an ocean and threw marine aerosols into the stratosphere. The impact of a comet less than one kilometer in diameter could have loaded the sky with enough debris to generate multiple successive years of cooling. Even after volcanic eruptions could again be convincingly tied to 536 CE cooling, some scientists argued that an asteroid 640 metres in diameter crashed into Australia, compounding the chilling effect of volcanic eruptions and carving out the Gulf of Carpentaria.

The impactor theory failed to convince many for long. Michael Baillie, a tree ring expert (or "Dendrochronologist") who first advocated the theory in a 1994 article, sided with volcanic explanations after glaciologist Lars Larsen and his team found evidence for a major eruption in multiple ice cores at both poles. This big, low-latitude, Tropical event was affixed a date of 533/534 ±2 CE. It seemed to explain why the "sun’s rays," according to John of Ephesus, "were visible for only two or three hours a day" in 536/37 CE. Larsen also drew attention to "an even larger" Northern Hemisphere deposit, which he dated to 529 ±2 CE. This may not have seemed important at the time, since there are no written sources that suggest anything strange about 529 CE. Yet, only months later, Baillie drew on a growing quantity of tree ring data to suggest that both newly discovered eruptions be moved forward by six or seven years. This adjustment offered an explanation for the unusual tree-ring signals he had highlighted in the early 1990s.

Tree ring data significantly altered scientific understandings of what happened in the sixth century. Independently of texts and ice, tree rings suggest a major disturbance in 536 CE. Tree ring data, unknown to Stothers and Rampino in the 1980s, give perhaps the best record of the sixth-century event. They give annual information with an objectivity that sixth-century historians cannot match. Together, they have a temporal and spatial "awareness" no written source can rival.

Mediterranean texts describe the 536 event as 12 or perhaps 18 months long, but Baillie surveyed trees from Ireland, Germany, Scandinavia and the U.S.A. that clearly show that the event lasted for roughly a decade. Tree rings also demonstrate that the 536 event was not a Byzantine oddity. Rather, it was vast: hemispheric or even global. Trees also reveal not one steady stretch of poor growth but a marked departure from normal growing conditions, with acute troughs and peaks. Some scholars therefore believed that a cluster of stratosphere-clouding phenomena were to blame, not a single cataclysm. The first nadir was in 536-537 CE, while the second, and more pronounced, was in 540-541 CE. More recent tree ring studies have highlighted a third low in 546-547 CE. This one, and another in the early 550s, were already visible in Baillie’s original work, but they were not much discussed.

Over the last twenty years, tree ring studies have confirmed that the 536 event was hemispheric, and at a point global, and that it lasted for more than a decade. Multiple tree ring temperature reconstructions have found several of the coldest growing seasons (typically June-August) of the last two (or, in some cases, seven-and-a-half) thousand years fall within the sixth-century downturn.

A few examples: a 1993 paper identified 536, 535, and 541 CE as the second, third, and fourth-coldest growing seasons in a 2,000-year-long chronology from Sierra Nevada. A 2001 paper used a Mongolian tree ring series that was nearly as long, and found unusually chilly temperatures from 536 to 545 CE, with low points in 536 and 543 CE. A 2015 study used a composite northern hemisphere chronology stretching back to 500 BCE, and established the successive decades of 536-545 and 546-555 as the coldest and tenth-coldest decades in the series. According to the same series, six of the thirteen coldest years between 500 BCE to 1250 CE happened during the sixth-century climatic downturn.

The "Baillie bump," the forward-pushing of Larsen's eruptions (and now most first millennium eruptions detected in ice), placed major volcanism at each of the cooling episodes identified in tree ring data. Michael Sigl and a team of scientists recently included these results within an important synthesis of glacial volcanic eruption chronologies. It is still not clear which volcanoes erupted in 535/536 and 539/540 CE, but a cluster of volcanoes seem to have caused the downturn.

Still, there may be room to doubt whether Cassidorus and company took in a hemispheric event in 536 CE. They may well have witnessed a local disturbance. Procopius has Vesuvius bubbling, but not erupting, in 536 CE. Whether this ‘extinguisher or all things green’ erupted around then - or perhaps another nearby mountain - we do not know. Minor, nearby volcanism may have coincided with a much larger, distant eruption. One would have veiled Mediterranean skies, while the other marked the world’s trees. Tree rings from Constantinople’s hinterland may support this theory, since they have failed to reflect a major change in growth from 536 to 550 CE.

Of course, it may still be that an impactor near-simultaneously fell to Earth from space. Dallas Abbott and her team have recently found iron oxide, silicate spherules, and other ejecta indicators in the melt-water of a portion of a sixth-century Greenlandic ice core. They interpreted a high concentration of calcium as calcium carbonate, a main component in seashells, and detected tropical aquatic microfossils: a first for Greenlandic ice. It is evidence for an impact at sea, which then sent marine aerosols into the stratosphere.

For years, the 536 event or 536-550 CE downturn figured as a particularly cold stretch (in fact the coldest) in a long cool phase that set in more than a century before 536 CE and has many names: The "Vandal Minimum," the "Early Medieval Cold Period," or the "Migration Period Pessimum." Very recently, a multidisciplinary study concluded that that the 536-550 event triggered a longer cold period within this Minimum. They call it the "Late Antique Little Ice Age," and argue that it was possibly even chillier and more unstable than the better-known early modern Little Ice Age.

Did this cooling have profound consequences for sixth-century societies? Maybe, yet historians came to the 536 event rather late. In 2005, historian Antti Arjava wrote an interdisciplinary appraisal of the evidence for a sixth-century cooling event. Aside from Arjava, the few historians who have wrestled with the clouding have not attempted a complete or current synthesis of the written and scientific evidence. Arjava's paper has therefore served as the main conduit for historians and archaeologists for the science surrounding the 536 event. However, Arjava wrote his paper in the years when scientists could not match the event with a volcanic eruption. The paper plays up the cloud’s mysteriousness, and diminishes its extent and impact. A reading of John the Lydian’s account, one fuller and closer than that offered by Stothers, led to the conclusion the event was Mediterranean specific, more of a fog than a veil, and damp, not dry. That and the lack of consistent evidence for poor harvests and food shortage in the 530s suggested the cloud had little effect on contemporary societies.

Much has changed since 2005. It is more difficult now to diminish the downturn or doubt that it triggered a marked, though temporary, demographic contraction in many regions of the world through its effects on plants. However, minimalist readings remain popular. They are still, if mostly through Arjava, a reaction to a pair of catastrophist books on 536 published in 1999 by Keys (Catastrophe) and Baillie (Catastrophic Encounters with Comets). The books argued for far-reaching and at times unfathomable historical consequences from mystery clouding, from Teotihaucan’s fall to China’s reunification, from Islam’s emergence and Charlemagne’s birth to England’s colonization of North America and Japan’s modern nation state. A reluctance to engage with the palaeoclimate sciences and a willingness to write nature out of history have allowed historians to dismiss the significance of the 536 event for contemporary peoples.

Recently, more scientifically-minded historians, such as Michael McCormick, have offered more appropriate (if maximalist-leaning) narratives, in which cooling had moderate implications for sixth-century peoples. A vast, near-unparalleled environmental event need not have cataclysmic consequences to warrant study. Histories of resilience and adaptation to sudden and dramatic climate change should be as important and intriguing as histories of failure and collapse. This is clear in new work on the effects of the downturn, from the Yucatán to Fennoscandia, which emphasizes coping strategies and a certain hardiness in those that lived beneath the veils.

Mayan Calakmul’s largest structure, Structure II. With roughly 6,200 constructions spread out over about 30 square kilometres in the late Classic period, the city of Calakmul (now in Mexico’s Campeche State) experienced rapid growth during the sixth-century "hiatus." This interval of debated tumultuousness between the early and late Classic phases saw a leveling off (or decline) in stelae and monumental building at several Mayan locales as well as (perhaps dramatic) population contraction. Richardson Gill (in his The Great Mayan Droughts) argued the downturn caused this break in activity and drawing on palaeoclimatology (from other world regions) assigned the hiatus a firm start date of 536 CE. Built atop a preclassical stucco-decorated plaza, Structure II was an important building throughout the Classic period. Fodor’s Cancún, Cozumel, Yucatán Peninsula recommends a stop at the ‘vast’ and ‘lovely’ but little-visited Calakmul, which in its "heyday" (between 542 and 695 CE) numbered at least 50,000 people. A climb up the pictured pyramid allows for a "soaring vista."

Although not everyone would have come out from under the dust worse off, it is important to not let the pendulum swing back too far. After all, there are indications from across Eurasia of subsistence crises. Read together, these reports suggest a rather uneven occurrence of downturn-triggered crop failure and genuine famine. That clouding density and duration undoubtedly varied, and people were not everywhere equally vulnerable, might account for this patchiness. So too the concurrence of other natural and cultural pressures in some areas.

It should be emphasized that large eruptions do not simply chill the world. The effects on weather and climate are non-uniform. They are regional and can differ markedly, as Pinatubo and Tambora have shown. Tropical eruptions, such as the 539/540 event, also exercise a different force on climate than high latitude Northern Hemispheric ones, like 535/536. For instance, major near-equatorial volcanism is known to cause winter warming in North America, Europe, and Russia, but winter cooling in Western and Eastern Asia. Extratropical Northern Hemispheric volcanism cools hot and cold seasons alike. Seasonality matters too. That high latitude eruptions seem to be more impactful if they occur in summer could indicate that the 535/536 eruption happened in that season.

A few contemporary reports of despair and devastation seem hyperbolic. Did Italian mothers really eat their daughters? Did three quarters of the population north of the Yellow river really die off? Yet neither they, nor less-sensational descriptions, should be written off as lacking any grounding in the immediate post-eruption reality. Most sixth-century societies were able to absorb one bad year, but very few were able to absorb two or three. Back-to-back(-to-back) years of poor growing conditions, caused by a sharp cooling of average temperatures, were certain to take a toll.

An eruption cluster - multiple Tambora-like events within a few years of each other - caused the mid sixth-century downturn. Whether an impactor was roughly coincident is uncertain. The variability of the effects of both eruptions on climate and the extent and regionality of the loss of life are uncertain as well. Sixth-century cooling may well have helped cause the outbreak of the "Plague of Justinian" - the so-called "First Bubonic Plague Pandemic" - with profound demographic consequences. This link, and other enduring mysteries of the sixth-century downturn, will be the subject of a future article on this site.

~Tim Newfield

Dr. Newfield will write a synthesis of the scholarship on sixth-century cooling, like this but more complete, in the The Palgrave Handbook of Climate History, edited by Franz Mauelshagen, Christian Pfister and Sam White.

Select Reading

D. Abbott et al, ‘What Caused Terrestrial Dust Loading and Climate Downturns between A.D. 533 and 540?’ Geological Society of America Special Papers 505 (2014).

A. Arjava, ‘The Mystery Cloud of 536 CE in the Mediterranean Sources’ Dumbarton Oaks Papers 59 (2005).

M. Baillie, ‘Dendrochronolgy Raises Questions About the Nature of the AD 536 Dust Veil Event’ The Holocene 4 (1994).

M. Baillie, ‘Proposed Re-Dating of the European Ice Core Chronology by Seven Years Prior to the 7th Century AD” Geophysical Research Letters 35 (2008).

U. Büntgen et al, ‘2500 Years of European Climate Variability and Human Susceptibility’ Science 331 (2011).

U. Büntgen et al, ‘Cooling and Societal Change during the Late Antique Little Ice Age from 536 to around 660AD’ Nature Geoscience 9 (2016).

B. Dahlin and A. Chase, ‘A Tale of Three Cities: Effects of the AD 536 Event in the Lowland Maya Heartland’ in G. Iannone ed., The Great Maya Droughts in Cultural Context: Case Studies in Resilience and Vulnerability (University of Colorado Press, 2014).

R. Dull et al., ‘Did the Ilopango TBJ Eruption Cause the 536 Event?’ American Geophysical Union Fall Meeting 2010 Abstract V13C-2370.

C. Hammer et al, ‘Greenland Ice Sheet Evidence of Post-Glacial Volcanism and its Climatic Impact’ Nature 288 (1980).

C. McKee et al, ‘A Revised Age of AD 667-699 for the Latest Major Eruption at Rabaul’ Bulletin of Volcanology 77 (2015).

L. Larsen et al, ‘New Ice Core Evidence for a Volcanic Cause of the A.D. 536 Dust Veil Event’ Geophysical Research Letters 35 (2008).

J. Luterbacher and C. Pfister, ‘The Year Without a Summer’ Nature Geoscience 8 (2015).

M. McCormick et al, ‘Climate Change During and After the Roman Empire: Reconstructing the Past from Scientific and Historical Evidence’ Journal of Interdisciplinary History 43 (2012).

E. Rigby et al, ‘A Comet Impact in AD 536?’ Astronomy and Geophysics 45 (2004).

A. Robock, 'Perspectives, Pinatubo Eruption: The Climatic Aftermath' Science 295 (2002).

A. Robock, ‘Volcanic Eruptions and Climate’ Reviews of Geophysics 38 (2000).

M. Sigl et al, ‘Timing and Climate Forcing of Volcanic Eruptions for the Past 2,500 Years’ Nature 523 (2015).

R.B. Stothers and M.R. Rampino, ‘Volcanic Eruptions in the Mediterranean before A.D. 630 from Written and Archaeological Sources’ Journal of Geophysical Research 88 (1983).

R.B. Stothers, ‘Mystery Cloud of AD 536’ Nature 307 (1984).

49:T3c8a,

Dr. Ruth Morgan, National Centre for Australian Studies, Monash University

Empty irrigation pipes along a dried irrigation canal near Stockton, California. Source: ProPublica, 25 June 2015.

At the 2016 American Society of Environmental History conference in Seattle, I joined Linda Nash (University of Washington), Char Miller (Pomona College), and Libby Robin (The Australian National University) to contextualize Western drought in environmental, historical and cultural terms. ‘Western drought’ in this instance referred to the region that the US Drought Monitor classifies as ‘West’, where some areas are still experiencing ‘exceptional’ drought conditions. Our discussion drew this Western experience into transnational conversation with histories of drought in Australia, further west across the Pacific. By providing a humanistic perspective of drought, the lens of environmental history complements the scientific study of climate conditions and offers valuable insights into how droughts have been understood and experienced over time.

The US Drought Monitor produces a weekly map of drought conditions based on measurements of climatic, hydrologic and soil conditions as well as reported impacts and observations drawn from around the United States. The US Drought Monitor is a joint initiative of the National Oceanic and Atmospheric Administration, the US Department of Agriculture, and the National Drought Mitigation Center at the University of Nebraska-Lincoln. Regional conditions as of April 12, 2016.

In late 2015, meteorologists watching the Pacific Ocean saw the signs of what the media described as the ‘Godzilla El Niño’. Ocean waters in the equatorial Pacific were unusually warm, one of the tell-tale signs that a very strong El Niño was brewing – stronger even than the catastrophic event of 1997-98. For the drought-stricken west coast of the United States, this forecast promised storms and heavy rains in California, while Australians feared the onset of worsening drought conditions over the inland areas of Queensland and northern New South Wales. Although this El Niño has yet to live up to the hype, with the Washington Post recently declaring it ‘dead’, its onset highlighted the climate connections between Australia and the American West and their shared experience of extreme weather events.

In August 2015, the Los Angeles Times compared the prevailing strength of the ‘Godzilla El Nino’ to the same time of year in 1997. The red and white patches depict the highest sea-surface heights above average, which indicate how warm sea-surface temperatures are above the average. Graphic: Bill Patzert, Climatologist, NASA Jet Propulsion Laboratory.

Prolonged dry spells lay the ecological and hydrological foundations for fires and floods. In the aftermath of the catastrophic Black Saturday bushfires of 2009, which claimed the lives of 173 Victorians, environmental historian Tom Griffiths explained, ‘These are wet mountain forests that burn on rare days at the end of long droughts, after prolonged heatwaves, and when the flume is in full gear. And when they do burn, they do so with atomic power’. Last year, wildfires burned across a bone dry American West and authorities fear what the 2016 fire season might have in store. Alternatively, in the boom and bust climate of the Murray-Darling Basin, historian Emily O’Gorman has shown how a downpour can turn into a flood if it is ‘not “cushioned” by already full rivers’, while historian Jared Orsi explores flood control in the ‘hazardous metropolis’ of Los Angeles.

Despite significant differences in population, economy and geography, both political and lay responses to drought over the past two decades reveal settler cultures that are at odds with the highly variable climates in which they live. In both Australia and the United States, drought has been a constant since English settlement: archaeologist Dennis Blanton has argued that Jamestown was founded at the height of an unprecedented dry spell, while environmental historian Richard Grove has shown that the arrival of the First Fleet in New South Wales in 1788 coincided with one of the strongest El Niño events in recorded history. Reconstructions of the pre-instrumental climate in southeastern Australia and California suggest the extent to which climate variability was a feature of colonial life.

Derived from qualitative sources, this table shows drought conditions in southeastern Australia between 1838 and 1860. Column R shows the number of regions affected by drought as a fraction of regions colonized by Europeans. Column M shows the number of months in a year that drought was reported. Source: Claire Fenby and Joëlle Gergis, 2012.

Although some part of Australia and the United States is almost always in drought, the visitation of such dry conditions continues to be framed as abnormal, rather than the expression of a variable climate. This water culture, as I and others have argued, is the product of the rise of large-scale public water infrastructure. By separating the means of water production and consumption, this mode of water management helped render invisible the processes of water delivery, thus allowing the illusion of endless water supplies to develop. Our responses to drought continue to favor restoring the illusion of endless water supplies, instead of addressing the cultures that perpetuate this unsustainable vision. Droughts, like all disasters, invite historians to peel away this veneer, laying bare deep-seated tensions relating to land, race, class, and politics that water scarcity only serves to heighten.

Like the Millennium Drought (1996-2010) in eastern Australia, the intensity of the recent drought in California (2011-) has been attributed to anthropogenic climate change. The IPCC warns that climate change will increase the likelihood and severity of such events in the future. In the southwest of Australia, meanwhile, climate change is also contributing to the regional drying trend that has been challenging local land and water managers since the 1960s. This drying trend is the result of the westerly winds, which are responsible for winter rains across southern Australia, inching south across the Southern Ocean and leading to greater snowfall in eastern Antarctica.

Australian rainfall projections under low, medium and high emission scenarios for different seasons, modelled by CSIRO and the Commonwealth Bureau of Meteorology based on IPCC scenarios. Source: The Guardian, 18 February 2014.

In light of these changing climates, an audience member asked us, what then are the role and value of climate and environmental histories? I argue that in these uncertain times, climate and environmental histories are more important than ever. Our research reveals the histories of past weather and climate events, how they were experienced, and how the experience and interpretation of such events has changed over time. We can also map the connections between climate events; historical patterns of vulnerability; and technological and cultural path dependencies. Environmental historians William Cronon and Tom Griffiths have long counselled their colleagues to tell stories about the past, for narratives have the power to inform and most importantly, engage.

Engagement is crucial for historians, not just through our stories but also through our research. Close collaborations with researchers and policymakers can reveal the historical thinking inherent to environmental management, while informing analyses of the present and plans for the future.

~Ruth Morgan

Bibliography

Australian Context

Deb Anderson, Endurance: Australian Stories of Drought, CSIRO, 2014.

Michael Cathcart, The Water Dreamers: The Remarkable History of Our Dry Continent, Text Publishing, 2010.

Tim Flannery, The Weather Makers: the History and Future Impact of Climate Change, Text Publishing, 2008.

Bill Gammage, The Biggest Estate on Earth: How Aborigines Made Australia, Allen & Unwin, 2011.

Don Garden, Droughts, Floods and Cyclones: El Niños that Shaped Our Colonial Past, Australian Scholarly Publishing, 2009.

Joëlle Gergis, Don Garden and Claire Fenby, ‘The Influence of Climate on the First European Settlement of Australia: a Comparison of Weather Journals, Documentary Data and Palaeoclimate Records, 1788-1793’, Environmental History, 15 (3), 2010: 1-23.

Tom Griffiths, ‘We Have Still Not Lived Long Enough’, Inside Story, 16 February 2009.

Robert Kenny, Gardens of Fire: an Investigative Memoir, UWA Publishing, 2013.

Ruth A. Morgan, Running Out? Water in Western Australia, UWAP, 2015.

Emily O’Gorman, Flood Country: an Environmental History of the Murray-Darling Basin, CSIRO Publishing, 2012.

Stephen J. Pyne, Burning Bush: a Fire History of Australia, University of Washington Press, 1998.

Comparative and Global Studies

Mike Davis, Late Victorian Holocausts: El Niño Famines and the Making of the Third World, Verso, 2001.

Henry F. Diaz and Vera Markgraf (eds), El Niño and Paleoclimatic Aspects of the Southern Oscillation, Cambridge, 1992.

Michael H. Glantz, Currents of Change: Impacts of El Niño and La Niña on Climate and Society, 2nd ed., Cambridge, 2000.

Richard H. Grove, ‘The Great El Niño of 1789-93 and its Global Consequences: Reconstructing an Extreme Climate Event in World Environmental History’, Medieval History Journal, vol. 10, 2007, pp. 75-98.

Richard H. Grove and John Chappell (eds), El Niño – History and Crisis: Studies from the Asia-Pacific Region, White Horse Press, 2000.

Ian Tyrrell, True Gardens of the Gods: Californian-Australian Environmental Reform, 1860-1930, University of California Press, 1999.

US Context

Dennis Blanton, ‘Drought as a Factor in the Jamestown Colony, 1607-1612’, Historical Archaeology, 34 (4), 2000: 74-81.

Mike Davis, Ecology of Fear: Los Angeles and the Imagination of Disaster, Metropolitan Books, 1998.

William DeBuys, The Great Aridness: Climate Change and the Future of the American Southwest, Oxford, 2011.

Norris Hundley Jr, The Great Thirst: Californians and Water, revised ed., University of California Press, 2001.

B. Lynn Ingram and Frances Malamud-Roam, The West Without Water: What Past Floods, Droughts and Other Climatic Clues Tell Us About Tomorrow, University of California Press, 2013.

Jared Orsi, Hazardous Metropolis: Flooding and Urban Ecology in Los Angeles, University of California Press, 2004.

Stephen J. Pyne, California: a Fire Survey, University of Arizona Press, 2016.

Marc Reisner, Cadillac Desert: the American West and its Disappearing Water, Penguin, 1993.

Marsha Weisiger, Dreaming of Sheep in Navajo Country, University of Washington Press, 2011.

Donald Worster, Dust Bowl: The Southern Plains in the 1930s, Oxford, 1979.

Donald Worster, Rivers of Empire: Water, Aridity and the Growth of the American West, Oxford, 1992.

4a:T442f,

Ask most people about climate change, and you will soon find that even the relatively informed make two big assumptions. First: the world’s climate was more or less stable until recently, and second: human actions started changing our climate with the advent of industrialization. If you have spent any time reading through this website, you will know that the first assumption is false. For millions of years, changes in Earth’s climate, driven by natural forces, have radically transformed the conditions for life on Earth. Admittedly, the most recent geological epoch – the Holocene – is defined, in part, by its relatively stable climate. Nevertheless, regional and even global climates have still changed quickly, and often dramatically, in ways that influenced societies long before the recent onset of global warming.

Take, for example, the sixteenth century. Relative to early twentieth-century averages, the decades between 1530 and 1560 were relatively mild in much of the northern hemisphere. Yet, after 1565, average annual temperatures in the northern hemisphere fell to at least one degree Celsius below their early twentieth-century norms. Despite substantial interannual variations, temperatures remained generally cool until the aftermath of a bitterly cold “year without summer,” in 1628. Since the expansion of the glacier near Grindelwald, a Swiss town, was among the clearest signs of a chillier climate, these decades are collectively called the “Grindelwald Fluctuation.” It was one of the coldest periods in a generally cool climatic regime that is today known as the “Little Ice Age.”

Length changes of four well-documented Alpine glaciers, based on historical sources.

Volcanic eruptions undoubtedly caused some of the cooling. In 1595, the eruption of Nevado del Ruiz released sulphur aerosols into the atmosphere, scattering sunlight and thereby cooling the planet. Just five years later, Huaynaputina exploded in one of the most powerful volcanic explosions of the past 2,500 years. Major volcanic eruptions following in close proximity to one another can trigger long-term cooling by activating "positive feedbacks" in different parts of Earth’s climate system. In the Arctic, for example, volcanic dust veils lead to chillier temperatures, which can increase the extent of Arctic ice that, through its high albedo, reflects more sunlight into space than the water or land it replaces. That in turn leads to even cooler temperatures, more ice, and so on.

However, the onset of the Grindelwald Fluctuation preceded the eruption of Nevado del Ruiz by some thirty years. Clearly, volcanoes were not the only culprits for the colder climate. Some scientists believe that low solar activity also played a role. Yet, although the sun was less active during the Grindelwald Fluctuation than it is today, it will still more active than it was in most other decades of the Little Ice Age.

Solar minima and maxima over the past 2,000 years. The Grindelwald Fluctuation divides the Spörer Minimum from the Maunder Minimum.

That leads us to our second assumption: the idea that anthropogenic climate change began with industrialization. Most scholars of past climate change would still agree, but that might be changing. Recently, a growing body of evidence has started to suggest that humanity’s impact on Earth’s climate might be much older. Human depravity, it seems, might have been to blame for the cooling of the sixteenth century.

Back in 2003, palaeoclimatologist William Ruddiman proposed that humans were to blame for preindustrial climate change, in a groundbreaking article that shocked the scientific community. Two years later, he thoroughly explained and defended his conclusions in book called Plows, Plagues, and Petroleum: How Humans Took Control of Climate. Ruddiman argued that humanity had slowly but progressively altered Earth’s atmosphere since the widespread adoption of agriculture. Some 8,000 years ago, communities in China, Europe, and India made room for agricultural monocultures by burning away forests. According to Ruddiman, the scale of deforestation was enough to steadily increase the concentration of atmospheric carbon dioxide. Then, from around 5,000 years ago, rice farming and, to a lesser extent, livestock cultivation slowly raised atmospheric methane concentrations. Ruddiman concluded that the cumulative effect of these anthropogenic greenhouse gas emissions was to gradually increase average global temperatures, and perhaps ward off another ice age.

Ruddiman also argued that, since the adoption of agriculture, temporary fluctuations in atmospheric carbon dioxide concentrations followed from dramatic changes in human populations. During major disease outbreaks, Ruddiman insisted, populations declined to such an extent that agricultural land went untilled on a vast scale. Woodlands expanded, pulling more carbon dioxide out of the atmosphere than the agricultural crops they replaced, and thereby cooling the planet. When populations recovered, farmers burned down forests and planted their monocultures, warming the Earth.

Mesoamerican infected with smallpox, from the Florentine Codex by Bernardino de Sahagún.

During the sixteenth century, Spanish soldiers and settlers established a vast empire by waging environmentally destructive wars on the indigenous peoples of central and southern America. They forced many of the survivors into new settlement patterns and gruelling forced labour. They also disrupted indigenous ways of life by appropriating, and often transforming, regional environments. Their animals, plants, and pathogens encountered virgin populations and spread rapidly. Indigenous communities in hot, humid climates were especially vulnerable to outbreaks of Eurasian crowd diseases, which included smallpox, measles, influenza, mumps, diphtheria, typhus, and pulmonary plague. Recent population modelling suggests that the population of the Americas declined from approximately 61 million in 1492 to six million in 1650.

By the late sixteenth century, this holocaust was well underway. Land previously colonized by indigenous communities through controlled burning or the planting of agricultural monocultures gradually reverted to woodlands. While all plants inhale carbon dioxide and exhale oxygen, tropical rainforests are much more effective carbon sinks than human crops. In the Americas, reforestation on a vast scale probably lowered atmospheric concentrations of carbon dioxide by 7 to 10 parts per million between 1570 and 1620. Human cruelty may therefore have contributed to the climatic cooling also caused by volcanic eruptions and, maybe, a decline in solar radiation relative to modern or medieval norms.

A Spanish depiction of Tenochtitlan, the Aztec capitol, 1524.

A growing body of scholarship now provides evidence for these relationships. However, there are many questions that must be answered before we can confidently conclude that depopulation helped trigger the Grindelwald Fluctuation, let alone other episodes of climatic cooling. For instance: did the cooling effect of sixteenth-century reforestation in the Americas overwhelm the warming influence of contemporaneous deforestation in China and India? Were invasive species introduced by Europeans into the Americas incapable of preventing reforestation? Was the pace of depopulation, and in turn reforestation, really so fast and so universal that it could substantially reduce atmospheric carbon dioxide concentrations over the course of a few decades?

It will take a while to answer these questions, but some scholars are already drawing big conclusions. Earlier this year, geographers Simon Lewis and Mark Maslin argued that the cooling set in motion by the depopulation of the Americas could be considered the beginning of the “Anthropocene,” the proposed geological epoch dominated by human transformations of the world’s environment. Dating big changes in geological time is tricky business. The changes must be visible in the global stratigraphic record – that is, in rock layers – and they must be traceable to a specific date. Lewis and Maslin lean on earlier environmental histories of the “Columbian Exchange,” the European transfer of plants, animals, and pathogens between the New and Old Worlds. The impact was a global biotic homogenization that, according to Lewis and Maslin, should be visible in the stratigraphic record. That still leaves them without a specific date, however. They settle on 1610, because that was when atmospheric carbon dioxide levels reached a minimum caused, they say, by European depopulation of the Americas.

Warships, stuck in the ice during the Dutch Revolt.

There may be one more wrinkle to this sad story. In a forthcoming book, I argue that the Dutch revolt against the Spanish empire was provoked, in part, by high food prices that followed from harvest failures during the chilly onset of the Grindelwald Fluctuation. Then, until the early seventeenth century, the Dutch rebellion benefitted from a chilly climate. Dutch fortifications routinely forced Spanish armies to stay in the field during the frigid winters of the Grindelwald Fluctuation. The effect on Spanish soldiers could be disastrous. It is possible, therefore, that Spanish conquests in one part of the world contributed to climate changes that benefitted a rebellion against Spanish rule in another.

If so, the Eighty Years’ War may provide one of the first examples of such a self-defeating climate history of violence. It was certainly not the last. Recently, interdisciplinary researchers have found similar connections at work in the Syrian civil war. In a poorly governed society already destabilized by migrants fleeing the American invasion of Iraq, a severe drought caused, in part, by anthropogenic warming created fertile conditions for rebellion. The countries now at war in Syria and Iraq include those most responsible for the climate change that helped set the conflict in motion. Studying the Grindelwald Fluctuation may provide deep context for these relationships, by rooting them in a long history of violence and environmental transformation. It may also show that both assumptions commonly held about climate change are wrong.

~Dagomar Degroot

My thanks to professors John McNeill, Richard Hoffmann, and Sam White for suggesting sources and helping me think through these relationships.

Graph Source:

Nussbaumer, Samuel U. and Heinz J. Zumbühl, "The Little Ice Age history of the Glacier des Bossons (Mont Blanc massif, France): a new high-resolution glacier length curve based on historical documents." Climatic Change 111 (2012): 301-334.

On Volcanic Cooling:

Sigl, Michael, M. Winstrup, J. R. McConnell, K. C. Welten, G. Plunkett, F. Ludlow, U. Büntgen, M. Caffee, et al., “Timing and Climate Forcing of Volcanic Eruptions for the Past 2,500 Years,” Nature 523 (2015): 543–49.

On Anthropogenic Cooling:

Dull, Robert A., Richard J. Nevle, William I. Woods, Dennis K. Bird, Shiri Avnery, and William M. Denevan. “The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing.” Annals of the Association of American Geographers 100 (2010): 755–71. doi:10.1080/00045608.2010.502432.

Etheridge, D. M., L. P. Steele, R. L. Langenfelds, R. J. Francey, J.-M. Barnola, and V. I. Morgan. “Natural and Anthropogenic Changes in Atmospheric CO2 over the Last 1000 Years from Air in Antarctic Ice and Firn.” Journal of Geophysical Research: Atmospheres 101, no. D2 (1996): 4115–28. doi:10.1029/95JD03410.

Ganopolski, A., R. Winkelmann, and H. J. Schellnhuber. “Critical insolation–CO2 Relation for Diagnosing Past and Future Glacial Inception.” Nature529 (2016): 200–203. doi:10.1038/nature16494.

Hunter, Richard, and Andrew Sluyter. “Sixteenth-Century Soil Carbon Sequestration Rates Based on Mexican Land-Grant Documents.” Holocene 25 (2015): 880–85. doi:10.1177/0959683615569323.

Kaplan, Jed O. “Holocene Carbon Cycle: Climate or Humans?” Nature Geoscience 8 (2015): 335–36. doi:10.1038/ngeo2432.

Lewis, Simon L. and Mark A. Maslin. “Defining the Anthropocene.” Nature 519 (2015): 171-180.

Mitchell, Logan, Ed Brook, James E. Lee, Christo Buizert, and Todd Sowers. “Constraints on the Late Holocene Anthropogenic Contribution to the Atmospheric Methane Budget.” Science 342 (2013): 964–66. doi:10.1126/science.1238920.

Nevle, R.J., D.K. Bird, W.F. Ruddiman, and R.A. Dull. “Neotropical Human–Landscape Interactions, Fire, and Atmospheric CO2 during European Conquest.” The Holocene 21 (2011): 853–64. doi:10.1177/0959683611404578.

Pasteris, Daniel, Joseph R. McConnell, Ross Edwards, Elizabeth Isaksson, and Mary R. Albert. “Acidity Decline in Antarctic Ice Cores during the Little Ice Age Linked to Changes in Atmospheric Nitrate and Sea Salt Concentrations.” Journal of Geophysical Research: Atmospheres 119 (2014): 5640–52. doi:10.1002/2013JD020377.

Ruddiman, William. “The Anthropogenic Greenhouse Era Began Thousands of Years Ago.” Climatic Change 61 (2003): 261–93.

Ruddiman, William. Plows, Plagues, and Petroleum: How Humans Took Control of Climate. Princeton, NJ: Princeton University Press, 2005.

Ruddiman, William, Steve Vavrus, John Kutzbach, and Feng He. “Does Pre-Industrial Warming Double the Anthropogenic Total?” The Anthropocene Review 1 (2014): 147–53. doi:10.1177/2053019614529263.

Wang, Z., J. Chappellaz, K. Park, and J.E. Mark. “Large Variations in Southern Hemisphere Biomass Burning During the Last 650 Years.” Science330 (2010): 1663–66.

4b:T490f,

This semester, I taught my first course devoted exclusively to the environmental history of climate change. The course was, as one of my senior auditors pointed out, unusually ambitious. Luckily, I had a group of brilliant, hard-working students who embraced its challenges. Their coursework included a fifteen-page essay that connected a change in past global or regional climates to an episode in human history. They had to find a topic and then use a primary source to make an argument about that topic. They needed to support their argument using a blend of scientific and humanistic scholarship. The results were impressive, and you can read some of the abstracts here.

As my course reached its conclusion, I started thinking about how it could be improved for my next group of passionate Georgetown undergraduates. Courses dedicated largely or exclusively to climate history are only now becoming possible, so teaching guides are difficult to come by. With that in mind, I reached out to some of the environmental historians I respect most. I asked them some questions about teaching climate history to students, and I have copied their responses below. I have included my own reflections.

1. What is the biggest difference between teaching climate history and teaching other kinds of history?

Professor Richard Hoffmann, York University:

I have always taught climate history in the context of broader environmental history or even general survey courses. The introduction to history students of a new ‘historical agent’ and unfamiliar methodologies distinguishes climate history and several other aspects of environmental history (disease, agroecosystems). Perhaps oddly, undergraduates seem to me to take to the notion of climate having impact (but also assume a lot of determinism) much more readily than they grasp the need to understand palaeoscience.

Professor Alan MacEachern, Western University:

There are more graphs, I would say only somewhat facetiously. Keeling curve, pie charts, carbon cycle, etc. -- some History students struggled early on with the tables, graphs, & illustrations that a course in climate history requires. And we jumped right in, with a first class entitled “The Earth’s Climate Made Easy (I hope).” But students got a lot out of learning to read them – reading them for the narratives & for the limitations of those narratives. For example, to see how much the graphic representation of the Medieval Warm Period and Little Ice Age had changed from the 1990 IPCC to the 2007 IPCC is to see what’s gained and lost in a simplified narrative.

Professor John McNeill, Georgetown University:

In my case the biggest differences were that I team-taught with an earth scientist. He handled all lecturing on the physics of the climate system, and some of the changes in paleoclimate. I handled some of the latter, and all the impacts of climate shifts and shocks on human affairs. That made it a lot easier for me, because I did not have to answer questions about atmospheric Rossby waves. However, it also made for some discontinuity in the class, as we shifted back and forth from climatology to climate history.

I also felt the course was spottier, more episodic than my usual undergraduate classes. We began the chronological sequence 7 million years ago, with occasional backward glances to deeper time, and touched down at about two dozen moments between then and now. We employed a strong bias in favor of moments of climate change or extreme climate shocks and ignored almost everything in between. And I felt the course was more constrained by paucity of data from some parts of the world. Historians collectively have done a great job in the past 50 years of attending to the history of formerly neglected parts of the world. Climate history data are still rather thin for some regions, and it will take time, and possibly new forms of proxy evidence, to remedy that.

Professor Dagomar Degroot, Georgetown University:

For me, the immense temporal and geographic scales that climate history invites us to explore. My course began by showing why and how global climates fluctuated across tens and even hundreds of millions of years. It then connected climate changes to human evolution on 100,000-year scales. On the one hand, climate history provides a rare opportunity to introduce history students to the really deep past, and to explain why that past matters. On the other, that opportunity comes with risks. For example, we can easily fall into the deterministic trap of reducing human history to climate. Our courses can also lack coherence when we get into the most recent past. Because we suddenly have far more primary source accounts of human thoughts and actions, our temporal scale of analysis can abruptly narrow. We start to cover different topics: ideas of climate change, for example, that are simply impossible to reconstruct in any detail before the medieval period. Climate history, therefore, comes with unusual challenges, both for students (see below) and instructors.

2. What about climate history most challenges your students?

Hoffmann:

Accepting the need to cope critically with non-traditional source materials and evidence. Quantitative evidence, use of models, and theory are unfamiliar, even alien, to the mindset of many history students. In this, I’ll point out, climate history differs little from my early career experience trying to teach economic history and quantitative social history. Students will read right past graphs and tables, having learned in high school this method of avoidance. If you really wish to overcome this for at least the better students, you need to spend small group classroom time working laboriously through some such graphic presentations to force students to see how to draw conclusions. They then need to be walked through as small and clear a piece of palaeoscientific scholarship as we can find, so they see what the strengths and the limits of that data might be.

My best students in environmental history have either come from scientific backgrounds or realized early on the need to gain the expertise to be solid critical consumers of science to use it to help them understand the past.

MacEachern:

Perhaps the matter of scale – both spatial & temporal scale. How worthwhile is a micro study if it’s an outlier in terms of what’s happening on most of the planet or across a longer period of time? Conversely, how worthwhile is a macro study if sociocultural specificity is lost? Of course, those are questions for all students of history: even if we assume the usefulness of the past, what / whose specific pasts should we be sure to know, and what lessons can we take from those pasts?

…I’d add a second challenge: The disconnect between how long we’ve known about climate change and how little we’ve done with that knowledge. A student mentioned being blown away by Kenneth Hare’s pronouncement at the 1988 Toronto climate conference, that climate change is “the central environmental problem of our times” – emphasis in original. And it’s been a generation since then.

A climate reconstruction of the past two millennia, used in Degroot's climate history course. Source: IPCC 2014.

McNeill:

In our class I would guess the toughest challenge was handling two disparate sorts of data. While my colleague and I lectured on (and graded) only what we knew best, the students had no such luxury. So they had to master some technical and quantitative aspects of the climate system and atmospheric physics, but they also had to master the complexities of social change in wildly diverse cultural and political settings on which they had little background beyond what I was able to provide.

Degroot:

When my students signed up for my course, many did not know what to expect. Most thought they were taking a more traditional, narrowly focused history course, with a little bit of science thrown in. However, the first month of my course was all about Earth science and the distant, prehistorical past. We read some difficult articles and books that introduced my students to interdisciplinary methodologies and concepts. We interpreted graphs, graphs, and more graphs, with the occasional map thrown in. Some of my students acknowledged that they were much more at ease when we arrived at the more recent past, and human voices started appearing in course readings and lectures.

When I next teach my course, I must now decide whether to narrow its focus. It would, of course, be easier for me to teach a course on the last millennium of climate history. Doing that would let me devote much more time on some fascinating issues and concepts, including: how we reconstruct climate changes, what people might have thought about them, and how global warming was first discovered. However, students in other courses are rarely introduced to the perspective of the really deep past. Without the first month of my course, they might never come to understand how profoundly environmental changes have shaped humanity, and for how long humanity has transformed global environments. Climate history, therefore, forces us to make some hard pedagogical choices.

3. After your students leave your course, what concept pertaining to climate history do you most want them to remember?

Hoffmann:

Understanding climate as patterns and trends in the atmosphere which are manifest both in specific kinds of events (catastrophes and ‘sunny days’) and slow onset movements (changes in winter severity, precipitation totals, etc) visible only in retrospect and at different spatial scales. Learn why we would now rather refer, for example, to the “Medieval Climatic Anomaly’ instead of the “Medieval Warm Period” – and thus be open to different consequences for different human societies at the same time.

MacEachern:

Again, it’s a concept that pertains not just to climate history, but to all history: determinism. Mike Hulme has a nice line about climate history too often making the past seem “climate-shaped.” Coming in, some of the students believed that, since this was a climate history course, we would find everything in history to be attributable to climate. Instead, we repeatedly discussed what would be the appropriate description of climate’s role in history, and how that role changed from case by case, place by place, time by time.

McNeill:

I’d like to think they can remember more than one concept from our class! I’d like them to remember that climate has been changing, faster or slower, for time out of mind. I’d like them to remember that climate changes and shocks ripple through natural and human systems, affecting a wide range of things, beginning with agriculture but extending to less obvious areas, such as disease regimes, I’d like them to remember that human societies have responded and adjusted to climate change, although at times only at great cost. I’d like them to remember that most responses in times past involved migration.

Record-shattering global temperatures last month. Source: NASA GISS

Degroot:

I asked my students what they would take away from my climate history course. Here are some of their responses:

Climate change affected the global history of humanity, even in the deep past!
Climate change did not directly determine human history, and it will not directly determine our future. Climate change is one influence among the many that shape human action.
Relationships between climate changes and human histories were complex and sometimes counterintuitive. Sometimes they unfolded gradually, and other times they followed from extreme events.
Scholars should work with colleagues in other disciplines when reconstructing past environmental changes and their human consequences.
Primary sources must be read carefully, with an eye to who, why, and for whom they were written.
Anthropogenic climate change is already transforming our world. Without drastic action to reduce greenhouse gas emissions, our planet will look very different by the end of the century. The consequences will be especially devastating for already marginalized communities.

All of these lessons are important, but the last one is closest to my heart. As an environmental historian, I love teaching about the past in ways that change how students understand the present and the future.

4. In your opinion, how will the teaching of climate history change over the coming decade?

Hoffmann:

I’d like to hope you will be able to find more students in history classes better prepared to handle scientific and quantitative information and arguments . . . and not only because more students from science drop into your courses. It is also plain to me that you will have ever-increasing capabilities for interactive visual displays in the classroom setting, which you will need to employ as more than just eye candy and without letting such overwhelm critical thinking about how past people responded to and changed their experiences of climate events and trends.

MacEachern:

As with environmental history, there’ll be growing acceptance within the history field that this is history: that historians have a role to play in understanding past climates and humans’ relationships to climate, and that this is history that students – Arts, Science, and Environmental Science students – should know.

And there’ll be more & better potential textbooks. Perhaps not surprisingly, I struggled to find a book that mixed a global history of climate with a history of meteorology with a history of our understanding of climate change. Instead, I cobbled from Behringer’s Cultural History of Climate, Weart’s Discovery of Global Warming, Zeller’s Inventing Canada, & a wide range of essays.

McNeill:

That’s a tough one. I imagine there are 50 ways to teach climate history now and as more people get into it that number will climb. So there will be many simultaneous but not necessarily parallel directions of change. That said, I hope we can look forward to more data from the neglected parts of the world; finer resolution for some of the data we think we have; more careful correlation of textual and natural archives on the part of practitioners in the field; and greater rigor in the assertions about climate’s impact on societies. If we get some of these things, the teaching of climate history will become more compelling for students. Something also depends on what climate change and extreme climate events the next ten years bring. In this respect, the past we teach will depend on the future we await.

Degroot:

There will be ten more years of climate history. Many of my students were fascinated by the histories of the Syrian and Sudanese civil wars, which may have been provoked, in part, by climate change. Other students wanted to explore the probable relationship between anthropogenic warming and hurricanes Katrina and Sandy. Most of my students were concerned by the ongoing transformation of the Arctic. All of these changes – and many others – have unfolded in the last decade. I fear that, in the next decade, we will have many more examples of climate history to capture the attention of our students.

Many thanks to Professors Hoffmann, MacEachern, and McNeill for taking part in this interview during one of the busiest times of the year. The interview will be permanently featured on the redesigned website of the Climate History Network.

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Global temperatures in 2090-99, relative to 1990-99. Source: IPCC 2014

This week, roughly 40,000 delegates from 147 nations gather in Paris for the twenty-first annual "Conference of Parties" (COP21) in the fight against climate change. For the first time, participating governments will seek a legally binding agreement on mitigating and adapting to climate change. Their ambition will be to ensure that average global temperatures do not rise more than two degrees Celsius above their preindustrial averages. However, this goal now faces at least four serious challenges.

First, the governments of some developing countries, led by India, have insisted that relatively poor countries should not have to reduce their greenhouse gas emissions. They maintain that developed nations long exploited cheap energy to build their present wealth. These countries should therefore pay the price for global warming. Such thinking is not without merit, but it ignores the political challenges faced by governments in developed nations. It is also disingenuous: developing countries now account for such a large share of the world's carbon emissions that no cuts made by wealthy nations alone could sufficiently mitigate climate change.

Second, pledges currently made by participating governments would still lead to warming of nearly three degrees Celsius, well beyond the two degree limit suggested by scientists. Third, while that limit is the most ambitious goal we can now hope to achieve, it may not be enough to avoid catastrophic and irreversible changes in regional environments. Studies of past climates - many described on this site - have revealed the disturbing vulnerability of ecosystems and civilizations to even minor fluctuations in average global temperatures.

Finally, fourth, a poll recently carried out in twenty countries has revealed sharply declining popular support for ambitious climate change targets at COP21. This disheartening shift in public opinion may reflect new fears about terrorist attacks launched by ISIS, which appears to be the more pressing problem. Yet some recent scientific articles conclude that the Syrian civil war, and in turn the rise of ISIS, may have been partially enabled by climate change.

Nevertheless, the urgency of action has never been more clear. This year will be, by far, the warmest ever recorded, and October was an especially hot month even in that context. This is a map of global temperatures in October, relative to worldwide averages between 1951 and 1980:

Source: NASA GISSTEMP

The following graph compares average global temperatures this year with some other years of record-breaking month. It shows what can happen when an extreme El Niño compounds the warming influence of greenhouse gas emissions:

Source: NOAA NCEI

Just before the students of my climate history course left for their Thanksgiving holidays, they had to endure one of my gloomier lectures. I gave them a vision of how Earth's climate will change in the coming century. In the United States, the act of giving thanks for what we have is quickly followed by a mad drive to have even more, on "Black Friday" and "Cyber Monday." Yet, the science on climate change shows that, on a societal scale, our drive to consume is devouring our future.

After I gave my lecture, it occurred to me that, during COP21, this vision of the coming century should be widely shared by climate change researchers. It may be our best response to the headwinds that now challenge a comprehensive climate agreement.

I began my lecture by explaining that, according to model simulations in the latest IPCC Assessment Report, this is how global temperatures and precipitation patterns will likely change by 2081-2100, relative to averages in 1986-2005:

Source: IPCC 2014

That's according to middle-of-the road greenhouse gas emission scenarios (in other words, if we take only moderate action to reduce our carbon emissions). These maps reveal that regional differences in the scale of warming will dramatically increase the overall impact, for human beings, of even modest global increases in average annual temperatures. The Arctic will likely be much warmer and wetter in 2100 than it is today, for example, while Europe will probably be far drier and hotter.

The impact of these changes will be further exacerbated by an increase in the regional frequency of weather extremes. Hurricanes, typhoons, and cyclones may well become more severe, if not necessarily more common, and heatwaves will be far more frequent. The following maps demonstrate that, in many places, both droughts and floods will also be much more common in 2080-2099 than they were in 1986-2005. They depict changes according to very high warming scenarios.

Source: Royal Society, 2014

The warming of the Arctic climate is already transforming the "cryosphere," the part of the Earth where water remains frozen. Melting ice is contributing to sea levels that are already rising because water expands when it gets warmer. These changes will continue in the decades ahead. A recent study concluded that sea levels could rise by nearly seven feet by 2100. That would be enough to swamp many of the world's coastal cities.

However, this prediction may be underselling the threat, because it does not account for the catastrophic ice loss in Greenland and Antarctica. Scientists have recently discovered that Greenland is melting more quickly and more thoroughly than they had expected. The complete melting of the Greenland ice sheet will probably take thousands of years, but it will eventually raise sea levels by some 23 feet.

The story in Antarctica is far more complex. Scientists recently announced that the West Antarctic Ice Sheet has started an irreversible but relatively slow-moving collapse. This conclusion was not included in the fifth IPCC assessment report, but it will eventually raise global sea levels by a further 12 feet. Nevertheless, a new NASA study has found that an increase in Antarctic snow accumulation that began 10,000 years ago is adding enough ice to the continent to more than outweigh losses from the West Antarctic Ice Sheet. Within 20 to 30 years, however, Antarctic ice losses should start exceeding accumulation.

Even the IPCC's conservative sea level predictions are concerning. These maps compare sea levels in 1986-2005 to their projected averages in 2081-2100. Atmospheric and oceanic circulation ensure that sea levels are not uniform, and some of the most severe changes will affect the coasts of Africa.

Source: IPCC 2014

This widely shared highlight from the documentary Chasing Ice provides a dramatic example of the changes underway in Greenland:

Some of the most troubling manifestations of climate change are unfolding in the world's oceans. Approximately 30 to 40% of human carbon emissions dissolve into water. Some of these emissions react with water to form carbonic acid, which ultimately increases ocean acidity through additional chemical reactions. Oceans will probably become 170% more acidic by 2100. The current rate of acidification is 100 times faster than any other changes in ocean acidity over the last 20 million years.

Ocean acidification will have catastrophic consequences for many (but not all) kinds of marine life. It will depresses metabolic rates for animals such as jumbo squid, and dampen immune responses in animals such as blue mussel. By killing algae, it will threaten reef ecosystems by bleaching coral and reducing oxygen levels. The following maps show oceanic pH levels in 1850 (top) and, according to forecasts, 2100 (bottom). The lower the number (and warmer the colour), the higher the pH level (and more acidic the water).

Source: Ocean Acidification Summary for Policymakers, International Geosphere-Biosphere Programme

All of these forecasts assume that anthropogenic greenhouse gas emissions will keep the world's climate below so-called "tipping points" or "threshold values" that could set in motion some truly dramatic, planet-altering changes. However, these tipping points are poorly understood, and our emissions may well exceed them.

One of these tipping points would lead to the breakdown of the vast ocean current called the Atlantic Meridional Overturning Circulation (AMOC), which helps govern the world’s climate. When ice forms in the Arctic and northern Atlantic Oceans, water around it gets saltier and therefore heavier. When it sinks, water from farther south moves north to replace it. This brings heat far into the northern hemisphere. When ice melts on a huge scale, cold freshwater drains into the northern Atlantic and slows down the current.

Take a look at the map of October temperatures, at the top of this article. That cold spot near Greenland reflects meltwater from the Greenland ice sheet. The AMOC is already slowing down. Could the collapse of the Greenland ice sheet shut it down completely, and, ironically, bring bitter cold to Europe and North America?

More worrisome still is the risk of widespread melting of the permafrost, which currently stores some 1.4 trillion tons of methane. As a greenhouse gas, methane is 84 times more potent than Carbon Dioxide. The permafrost is already starting to melt on a large scale. In 2006, melting Siberian permafrost released 3.8 million tons of methane into atmosphere, but in 2013, that number increased to 17 million tons.

There is a feedback loop at work here, because melting permafrost warms the atmosphere, especially in the far north, which then leads to more melting. More dramatic melting of the world's permafrost would lead to more warming than is predicted by even the IPCC's worst-case scenarios. The map below depicts the global distribution of permafrost, and shows the scale of the potential problem:

Some the changes I've described will happen, no matter what we do. The complicated graph below depicts the predicted extent of global warming, according to different emissions scenarios. It demonstrates that, even if we dramatically and immediately slash our emissions, the globe will still warm by nearly two degrees Celsius, relative to twentieth-century averages. Yet it also shows that, by acting now, governments can avoid truly catastrophic warming. The world's future is in the hands of the delegates in Paris.

Source: IPCC 2014

In the coming century, even relatively modest global warming may well have devastating consequences for human beings and the species on which we depend. Climate historians have shown that the precise impacts will undoubtedly vary from society to society, and depend much on socioeconomic and technological changes that are, at present, difficult to predict. Predicted advances in biotechnology, artificial intelligence, and energy production, for example, may well transform human vulnerability to climate change. Nevertheless, a warmer world will be a planet less hospitable to human life.

The IPCC has published the following map of the ongoing environmental and social consequences of climate change today. If warming temperatures have already had profound global consequences, what will our future have in store?

Source: IPCC 2014

At COP21, international delegates have a chance to take the tough action that will let us avoid a future of climate change catastrophe. However, they will be under enormous pressure to avoid politically damaging agreements now. The warmer future, after all, still feels far off. Yet, in many respects, it is here already. In a year of wildfires, heat waves, catastrophic storms, and drought-fuelled conflict, the need to combat climate change should never feel more urgent.

~Dagomar Degroot

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Hurricane Joaquin on October 1st, 2015. NOAA.

Last week, millions of people across the eastern coasts of the United States and Canada faced a frightening prospect: landfall of a major hurricane to rival Sandy, or perhaps even Katrina. At noon on October 1st, Hurricane Joaquin churned over Samana Cay, the largest uninhabited island in the Bahamas, and perhaps the first land glimpsed by Columbus in 1492. Maximum sustained winds of 205 kilometres/hour made the storm a category three on the five-category Saffir–Simpson Hurricane Wind Scale. Just over an hour later, it had strengthened to a category four. At the time, every major American “model” that simulated the storm’s trajectory predicted that it would make landfall anywhere between South Carolina and New York.

Not two months earlier, I had moved to Washington, D. C., to take up a position as professor of environmental history at Georgetown University. I designed and currently teach a course that explores connections between climate change and our species, from the beginnings of human evolution to the looming catastrophes of the future. On the morning of October 1st, I prepared to lead my students through a discussion about the collapse of Mayan civilization, which coincided with a series of severe droughts around the year 900 AD. At the same time, I obsessively searched for the latest updates on the trajectory and growing power of Joaquin.

I concluded - very unscientifically - that there was about a one in two chance that the storm would hit Washington directly. Given the near record heat of the waters fuelling Joaquin’s rise, I guessed that there was a smaller, but still substantial, possibility that the storm would make landfall as a major hurricane. Georgetown rests on a hill, and my home does, too. Yet most of Washington was built across the low-lying terrain of a former swamp. The storm surge that would accompany a hurricane would probably cause widespread flooding, power outages, and loss of life. Scholars have long predicted that such a flood will happen in Washington, sooner or later.

Areas at risk in a storm surge, Washington D. C.

It was a surreal experience: buying survival supplies while planning a lesson on a disaster that afflicted another society, long ago, during another period of dramatic climate change. On this site, I have described the jarring psychological impact of the storm-shattered landscape, and reflected on the teachable moments that hurricanes can give us. Until October 1st, I had not grasped that moving to Washington might, sooner or later, give me an entirely new perspective on these issues. Perhaps I should have: I just reviewed Stuart Schwartz’s Sea of Storms: A History of Hurricanes in the Greater Caribbean from Columbus to Katrina. It’s a compelling book, and one that explores the environmental history of hurricanes that occasionally tear into the American coast.

That afternoon, I devoted the first half of my class to the teachable moment provided by Joaquin’s pending arrival. My students are a bright and diverse bunch, and there isn’t a history major among them. They had a great deal to say, from many fascinating perspectives, but our conversation was tinged with anxiety. Would we be back next week?

Of course, by October 2nd it was clear that Joaquin would veer east, into the Atlantic. In the great cities of the American Northeast, the threat passed with a whimper. Not so in South Carolina, which is still struggling with catastrophic floods that were fed by rain driven north by the hurricane. The people of the Bahamas suffered, too, as did the crew of the giant cargo ship, El Faro, which succumbed to winds, waves, and faulty engineering.

Hurricane Joaquin on October 1st. GOES West satellite image, NOAA.

Even for the millions who were more fortunate, there are lessons to be learned from the storm that didn’t come.

First, it is increasingly clear that cities previously at little risk from hurricanes now face the possibility of enormous destruction from storms fuelled by unusually warm water. Such storms can happen even in climates cooler than our own, but they are certainly more likely now. Scientists have reached that conclusion by modelling relationships between oceanic warming and hurricane frequency and severity. These connections are very complex, and some scholars have argued that hurricanes, cyclones, and typhoons might actually moderate warming at tropical latitudes, while accelerating it elsewhere. Others maintain that records of hurricane landfalls do not go far enough back in time for scientists to reliably find connections between warming and the storms.

However, two recent studies successfully reconstruct the deep history of hurricane frequency using “proxy” sources that have responded to changes in hurricane activity. In August, Michael Burn and Suzanne Palmer published an article in the journal Scientific Reports that reconstructs a millennium of hurricane landfalls using lake sediments. More recently still, lead author Christian Ercolani has published an article in the journal Quaternary Science Reviews that uses overwash deposits from Naples, Florida, also across a thousand years. Burn, Palmer, Ercolani, and their colleagues all find that hurricane landfalls were significantly more common in warm climates than in chillier regimes. Scientists are still debating whether modern warming is raising the frequency of all hurricanes, or “merely” severe hurricanes. Nevertheless, it seems clear that warmer waters are raising the chances of a catastrophic storm in the Caribbean, and the likelihood that northbound storms will remain hurricanes even in high latitudes.

More than 160 years of Atlantic hurricane trajectories, in a warming world.

Second, the National Hurricane Center needs a better supercomputer, and fast. Even on October 1st, the European Centre for Medium-Range Weather Forecasts predicted that Joaquin would veer out to sea. Its forecast provided some comfort for me on October 1st. I knew that the European supercomputer behind the forecast was more powerful than the one responsible for the National Hurricane Center’s Global Forecast System model, the best available in the United States. Because the European computer is more powerful, it can predict weather with a greater geospatial resolution – or precision – than its American counterparts. This means that the Europeans are often much better at predicting even severe weather that affects the United States. It’s been that way for a while. In 2012, the European model was days ahead of its American competitors in forecasting Hurricane Sandy’s disastrous turn west. A year later, American models predicted a giant blizzard in Washington that never hit, but the European model was right.

The European Center for Medium-Range Weather Forecasts supercomputer.

In fact, both continental European and British models are better than their U.S. equivalents. Yet European meteorological technology and knowhow are not somehow superior. The National Hurricane Center could simply replace its current supercomputer with one more powerful than its European rivals. More importantly, American researchers could work to improve how their computers gather and assimilate meteorological data to build an accurate model of changes in the atmosphere over time.

But that would require money, and here the problem will be familiar to scholars of American disasters. It is relatively inexpensive to fund preventative or predictive programs before a disaster, which greatly diminish the costs of that disaster. It is outrageously expensive to finance recovery after a disaster, especially when that disaster was not adequately predicted or prepared for. However, in just about every society, it is politically dangerous to oppose recovery funding – as Senator Lindsey Graham is now discovering – yet politically simple to reject funding for science that superficially has no acute need.

Here on the East Coast, we were lucky to avoid another hurricane Sandy last week. Yet we received yet another reminder that a warming climate is placing us at risk, and that we need better ways of predicting that risk. Hopefully, this time we’ll listen.

~Dagomar Degroot

Web Links:

Harry Enten, "Why Hurricane Joaquin Is So Hard To Forecast." FiveThirtyEight, September 30, 2015.

Jason Samenow, "What the European model ‘win’ over the American model in Joaquin means for weather forecasting." The Washington Post, October 6, 2015.

Marshall Shepherd, "Some Perspective On European Vs American Weather Models After Hurricane Joaquin." Forbes, October 3, 2015.

Nate Cohn, "Hurricane Joaquin Forecast: Why U.S. Weather Model Has Fallen Behind." The New York Times, October 2, 2015.

Scholarly Sources:

Christian Ercolani et al., "Intense Southwest Florida hurricane landfalls over the past 1000 years." Quaternary Science Reviews 126 (29015): 17-25.

Kerry Emanuel "The Hurricane—Climate Connection." Bulletin of the American Meteorological Society 89: ES10-ES20.

Margaret C. Stewart, "The dynamic role of social media during Hurricane #Sandy: An introduction of the STREMII model to weather the storm of the crisis lifecycle." Computers in Human Behavior, 22 July 2015.

Michael Berlemann, "Hurricane Risk, Happiness and Life Satisfaction. Some Empirical Evidence on the Indirect Effects of Natural Disasters." Jahrestagung des Vereins für Socialpolitik 2015: Ökonomische Entwicklung - Theorie und Politik, 2015.

Michael J. Burn and Suzanne E. Palmer, "Atlantic hurricane activity during the last millennium." Nature 5 (2015).

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It is only September, but, absent a massive volcanic eruption or asteroid impact, 2015 will be, by far, the hottest year on the instrumental record. The culprit is a massive El Niño that is compounding the warming effects of rising greenhouse gas emissions. This year’s scorching heat will mean that the three hottest years on record will have occurred within the same five-year stretch: in 2010, 2014, and 2015.

In June, scientists with the National Oceanographic and Atmospheric Administration (NOAA) published a major article that measures the rate of global warming in light of this recent heat. The article uses a suite of new sources on land and across the oceans to provide a comprehensive temperature reconstruction from 1880 to the present. Many of these sources provide meteorological data of unprecedented accuracy. The new temperature reconstruction includes especially substantial corrections to previous global sea surface temperature statistics from the years 1880 to 1940. It also makes minor adjustments to temperature reconstructions of the last twenty years. In fact, using their new data, the NOAA scientists conclude that global temperatures have increased steadily since 1950. This is a major finding that contradicts the popular idea of a “pause” or “hiatus” in recent warming.

According to climatologist Gavin Schmidt, director of the Goddard Institute for Space Studies, “the fact that such small changes to the analysis make the difference between a hiatus or not . . . underlines how fragile a concept [the pause] was in the first place.” So how did that pause become such an influential idea? Given the forces behind record-setting temperatures this year, it is not surprising that the answer must begin with another major El Niño, eighteen years ago.

El Ninos compared. Source: NASA JPL, Bay Area News Group

From 1997 to 1998, that record-breaking El Niño slowly uncoiled across the tropical Pacific. In an El Niño, trade winds that normally blow from east to west slow down, lowering the layer of water that divides the upper from the lower ocean. That, in turn, reduces the efficiency of cool, deep-water upwelling. Warmer sea surface temperatures in the equatorial Pacific extend far to the east, and reshape atmospheric circulation around the world. In 1998, global temperatures rose sharply. Temperature records are usually set by a hundredth of a degree Celsius, but temperatures in 1998 exceeded the previous high-water mark by a tenth of a degree. It was the meteorological equivalent of Usain Bolt’s performance at the 2008 Olympics.

The mechanism by which El Nino affects the world's climate. "Atmospheric bridge" by Giorgiogp2 - Own work. Licensed under CC BY-SA 3.0 via Commons. https://goo.gl/EMTxYU

Looking back in 2001, the Intergovernmental Panel on Climate Change (IPCC) concluded that the 1998 spike in Earth’s temperature was an “extreme event,” even in the context of human-caused climate change. Inevitably, global temperatures cooled in the immediate wake of the great El Niño, although they remained much higher than the twentieth-century average. Still, to some, the warnings of climate scientists had suddenly become incompatible with the recent instrumental record. The idea of the “pause” was born.

Global warming sceptics quickly sought to popularize the concept. Naomi Oreskes and Eric Conway recently chronicled how some activist scientists have, for decades, derailed the public discourse on science that appears to challenge the unfettered workings of the free market. They tried to undermine, for example, science that links cigarette smoke to lung cancer, and chlorofluorocarbons to the Ozone Hole. They lost those battles, but found greater success in their fight against climate science. At every step, they have deployed the weapon of doubt. If the science that supports regulation can be made to sound uncertain, it can hardly serve as a foundation for government policy.

Already in 2006, palaeontologist Robert Carter, for instance, insisted that temperatures had remained steady for eight years, since 1998. In his telling, the science behind global warming appeared anything but settled. Carter, a well-known denier of anthropogenic warming, co-authored a notorious paper in 2009, which argued that El Niño events account for most of the changes in global temperature over the past fifty years. Three years later, Carter admitted that he received a monthly salary from the Heartland Institute, an influential organization committed to denying global warming. Regardless, Carter made an error that is also committed by better-intentioned sceptics of anthropogenic climate change. He identified a climatic trend by cherry picking a past date - an abnormally warm year - that allowed him to argue for recent cooling.

Even many scientists who agree with the scholarly consensus on global warming believed that the steady rise in Earth’s temperature had slowed - but not stopped - since 1998. As reported on this website, most of their research tied this supposed slowdown to one of two sets of variables. Some scientists argued that entirely natural causes had temporarily reduced the amount of solar radiation reaching the Earth. For example, as I reported on this website, one influential article blamed a recent spate of small volcanic eruptions. Other scientists more persuasively concluded that different parts of the climate system appeared to absorb more heat than had been thought possible. The oceans were widely cited as the destination for warmth that might otherwise have reached our atmosphere.

Nevertheless, the so-called “pause” in global warming barely registered in the public consciousness until early 2013. In January of that year, an article by lead author James Hansen – perhaps the most responsible and vocal voice in global warming scholarship – began with alarming news. In 2012, it announced, temperatures the world over had been 0.56 degrees Celsius warmer than the 1951-1980 base average. This was in spite of a La Niña that had chilled the waters of the equatorial Pacific, and therefore had the opposite effect on global temperatures of an El Niño.

Unfortunately, Hansen’s report contained a misleading and ultimately disastrous headline. Under “Global Warming Standstill,” the report noted that the five-year running mean of global temperature “has been flat for the past decade,” despite a steady (if slowing) increase in greenhouse gas emissions. The report speculated about possible reasons, but concluded that the most likely culprit was probably El Niño conditions early in the period, followed by La Niña episodes in more recent years. In years less troubled by these conditions, temperatures continued to rise at the rate they had in the previous three decades.

Google searches for "Global Warming Pause," as of September 30th, 2013. Source: Google Trends/Maggie Severns.

In March, an influential piece in The Economist misinterpreted this part of Hansen’s article. It began by declaring that, “over the past 15 years, air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar.” The article did not deny the existence of warming, and concluded that the recent pause was “hardly reassuring.” Nevertheless, it suggested that Earth might be less sensitive to our carbon emissions than scientists had previously believed. The Hansen article, remember, had reached entirely different conclusions.

The Economist article provided an opening for sceptics of climate change to push the narrative of the unexplained pause. Meanwhile, as chronicled by Chris Mooney, the IPCC prepared to release its fifth assessment report. In August, a leaked draft was released to the press. It contained descriptions of the pause that, when read in isolation, appeared to confirm the Economist article. According to one of the report’s lead authors, Dennis Hartmann of the University of Washington, public pressure convinced the scientists that they “had to say something” about the pause. They were hesitant, because the fifteen years between 1998 and 2013 were too short to reliably reflect a climatic trend. Yet before they had finalized their interpretation of the pause, it reached journalists who were only too eager to sacrifice scientific accuracy for sensationalistic headlines.

Not all proponents of the pause were scientifically illiterate, or associated with global warming denial. For example, in September 2013, Berkeley physicist and converted climate sceptic Richard Muller announced that the “global warming crowd has a problem,” because, “despite a steady escalation of greenhouse gas emissions into the atmosphere, the planet’s average surface temperature has remained pretty much the same for the last 15 years.” Muller argued that he had more or less predicated this pause back in 2004. It was in a critique of the so-called “hockey stick” graph that famously illustrated global warming (and has been recently vindicated). In 2004, Muller warned that, were the graph taken seriously, many would see inevitable, natural variations in temperature as undermining the case for anthropogenic climate change. In 2013, it seemed that Muller might be right.

Then, in late September, the IPCC finally released its completed fifth assessment report. As I described on this website, the report acknowledged a slight slowdown in the rate of global warming from 1998 to 2012. However, it weakened the previous draft’s description of a “pause” or “hiatus.” It confirmed that every decade in the past thirty years had been successively warmer than any previously recorded decade. As I wrote in 2013, it also explained that “the presence of short-term fluctuations in climate does not throw into doubt the existence of long-term climatic trends.” As one might expect, many sceptics met the final report with derision.

Previous NOAA temperature reconstructions in red (for land surface temperatures) and blue (for sea surface temperatures). Corrections in the new article are in black.

Fast forward to the present, and 2015 is set to be another meteorological equivalent of Usain Bolt's Olympic run. As in 1998, it looks like the previous record temperature will be broken by a tenth of a degree Celsius. Perhaps the narrative of the pause is now on its deathbed. Yet the idea of a recent slowdown in warming persists in very informed circles. In an elegant article published in the journal Science, climatologist Kevin Trenberth responds to the NOAA paper by taking issue with any warming trend that starts in 1950. After all, this was at the beginning of a so-called “big hiatus” in warming that chilled the world between 1943 and 1975. If sceptics should not cherry pick the start date of their temperature series by choosing an abnormally warm year, climatologists should not do the same by selecting a very cold year.

Interestingly, the big hiatus, which is well supported by robust science, was probably also caused by human activity. Aerosols released into the atmosphere by human pollution probably cooled the world, until clean air acts were passed in the 1970s. In the past, anthropogenic climate change could warm or cool the globe, and involve many kinds of human activity.

Overall, Trenberth supports the major findings of the NOAA scientists. He argues that there may have been a slight slowdown – not a pause – in the rate of global warming, driven at least partially by natural variation in, for example, the Pacific Decadal Oscillation (which includes El Niño and La El Niña). Yet he agrees that temperatures are rising quickly once again, and that the slowdown has probably ended.

Earlier this year, record-breaking wildfires spread across North America, while heat waves killed thousands in Europe and India. Sea levels, it seems, are warming and rising much faster than even the IPCC had predicated. The costs of climate change inaction have become increasingly clear. Carbon emissions have stagnated or declined in many developed countries, yet it is far from enough. Without drastic action, the weather of 2015 is only a precursor of things to come.

~Dagomar Degroot

Sources:

Hansen, J., M. Sato, and R. Ruedy. "Global Temperature Update Through 2015." 15 January, 2013. Available at: http://www.columbia.edu/~jeh1/mailings/2013/20130115_Temperature2012.pdf

Karl, Thomas R. et al. "Possible artifacts of data biases in the recent global surface warming hiatus." Science 348: 6242 (2015): 1469-1472.

Trenberth, Kevin E. "Has there been a hiatus?." Science 349: 6249 (2015): 691-692.

Trenberth, Kevin E. "The definition of El Nino." Bulletin of the American Meteorological Society 78: 12 (1997): 2771-2777.

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A Syrian refugee camp near Turkey. Source: Gregorio Borgia, Associated Press.

Across much of the world, climate change is making, or will soon make, environments less capable of supporting human life. Anyone who has seen the movie Mad Max will be familiar with the assumption that a hotter, and, in some places, drier climate will drive people to greater competition. When that competition is for the essentials of life, and there is not enough to go round, people resort to violence. In short: global warming could make war even more common than it is today.

In Syria and Iraq, we may be getting a glimpse of what such a future might look like. Earlier this year, a team led by climatologist Colin Kelley of the University of California published an article in Proceedings of the National Academy of Sciences that connected climate change to the ongoing civil war in Syria. Between 2006 and 2009, the people of Syria suffered during the most severe drought that country has experienced since the beginning of its instrumental record. As water became scarce, crops failed, and cattle died on a huge scale. As many as 1.5 million Syrians, out of a population of just over 20 million, moved from the countryside to the outskirts of already overflowing cities (Kelley et al., 3242).

Out of work, desperate, and living in poorly planned, crime-ridden neighbourhoods, many refugees were quick to revolt against a brutal regime that had long avoided such challenges. There is a mountainous literature that supports the idea that rapid and unexpected population growth can destabilize a society (or indeed, any population of living beings). Certainly, the population of Syrian cities surged. A Syrian farmer quoted by Kelley and his coauthors confirmed that “of course” drought, migration, and unemployment had pushed many toward rebellion. According to the farmer, “when the drought happened, we could handle it for two years, and then we said, ‘It’s enough’” (Kelley et al., 3245).

A Syrian refugee near Azaz, Syria, on February 17th, 2013. Source: Manu Brabo, Associated Press.

In Syria, connections between drought, dearth, and rebellion therefore seem clear. But did global warming play a role by starting the Syrian drought? Kelley and his coauthors think so. In order to find out, they needed to separate the influence of anthropogenic climate change from the natural variability of the Syrian climate. In the past, that variability has been sufficient to stimulate droughts across Syria, most recently in the 1950s, 1980s, and 1990s. However, precipitation in the country has been declining steadily for at least 80 years. According to computer simulations, westerly winds carrying moist airs from the Mediterranean have weakened, while warmer temperatures have increased rates of evaporation. In other words: less water arrives in Syria from elsewhere, and the water that does appear is vaporized more quickly than before (Kelley et al., 3245).

According to Kelley and his coauthors, the global climate models used by the IPCC approximately match the observational record of Syria’s climate over the last century. They reveal that the warming, drying trend in Syria is almost certainly caused by carbon released into the air by human beings. Computer simulations used by Kelley and his coauthors ultimately show that the 2006-2009 drought was two to three times more likely to occur in today’s climate than the one that preceded it. That still does not “prove” that climate change caused the Syrian drought, but demands for proof usually come from those who do not understand how research works. Scientists and other scholars uncover probable relationships, because we can never be absolutely certain about anything. Kelley and his colleagues have shown that we can be quite sure that catastrophic drought in Syria was related to a warmer, drier climate (Kelley et al., 3245).

Changes in the humidity of airflow around Syria, where red = drier, and blue = wetter. Source: Kelley et al., 3245.

Nevertheless, the authors acknowledge that climate change did not simplistically “cause” drought and civil war in Syria. They cite the destabilizing corruption of the Assad regime, and the extreme social inequality it fostered. They could have also mentioned that secular, despotic regimes, like the one led by Bashar al-Assad, were threatened by both liberal and fundamentalist resistance movements during the “Arab Spring.”

Moreover, Kelley and his coauthors find that, in 2006, Syria was unusually vulnerable to drought and its consequences. Bashar’s father, Hafez al-Assad, unsustainably intensified agricultural production in ways that strained already precarious water resources. In particular, irrigation farming severely depleted groundwater, drying the Khabur River and removing an essential buffer between dryness and agricultural collapse. Drought in the 1990s had also undermined the agricultural sector in Syria, which could not recover fully before 2006. Finally, the 1.5 million refugees who fled the effects of drought joined an existing refugee crisis caused by the American invasion of Iraq (Kelley et al., 3241).

Some scholars, like political scientist Thomas Bernauer of the Swiss Federal Institute of Technology, have even cast doubt on the connection between drought and the Syrian civil war. Indeed, we have a tendency to assume that resource shortages lead to conflict, but research in environmental history has shown that this view can be ahistorical. Take rivers that are split between different communities, or “users.” Actions by upstream users can have severe consequences for downstream users. In periods of scarcity, attempts by upstream users to irrigate arid environments with river water, for example, may convince downstream users that violence is the only way out. Yet there is ample evidence to suggest that initial competition for river resources can lead to cooperation. When lives and livelihoods are all tied to the same precious water supply, competition is likely to be counterproductive in the long run. Severe storms provide further examples. Much was made of so-called “looting” in the wake of hurricane Katrina. In fact, disaster relief in the wake of major hurricanes and cyclones has repeatedly linked communities to networks of national, or even global, cooperation.

Philippine survivors gather around a U.S. Navy helicopter in the wake of Typhoon Haiyan. Source: defenseimagery.mil.

Nevertheless, outside observers and Syrians themselves have made a convincing case that, in Syria, a severe drought caused profound socioeconomic disruptions, which in turn contributed to rebellion and civil war. Kelley and his coauthors have shown that climate change played a significant role in making that drought more likely. Ultimately, their research raises some important lessons for our understanding of relationships between climate change and conflict. It seems that global climate change can act as a catalyst for violence when it causes disruptions in regional weather that happen suddenly, provoke shortages of food and employment, and occur in an unstable socioeconomic context.

Even then, studies in climate history demonstrate that links between moderate climate change and war are never straightforward. Let us hope that this does not change in a much warmer future.

~Dagomar Degroot

Source: Colin P. Kelley, Shahrzad Mohtadi, Mark A. Cane, Richard Seager, and Yochanan Kushnir, "Climate change in the Fertile Crescent and implications of the recent Syrian drought." PNAS 112:11 (2015): 3241-3246

Read an interview with Colin Kelley.

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An artist imagines what Mars once looked like. Credit: ESO/M. Kornmesser/N. Risinger (skysurvey.org)

Climate historians explore how climate change influenced human history. Until now, their research has investigated environmental changes on Earth, and with good reason. Many examine how climate change affected human beings in centuries when space travel could scarcely be imagined. Others are too concerned with contextualizing global warming to consider environments beyond Earth. However, recent breakthroughs in scientific understandings of Mars’s watery past suggest that climate history can, and should, expand into the Solar System.

For more than two decades, the presence of an ancient Martian ocean has been a source of academic controversy. In recent years, radar and visual maps provided by orbiting space probes have strongly supported the existence of an ocean, billions of years ago. The European Space Agency’s “Mars Express” orbiter, for instance, detected probable ocean floor sediments in regions ringed by ancient Martian shorelines. Scientists at the University of Colorado at Boulder also mapped river deltas on the Martian service that apparently fed into vanished oceans. Now, planetary scientist Geronimo Villanueva and a team of researchers have published an article in the journal Science that provides compelling new evidence for a vast, long-lived Martian ocean. Their article has received major media attention, and, as of this writing, is on the front page of CNN.

The Martian atmosphere, spotted by the Viking 1 Orbiter.

The sad history of the Martian environment has consequences for humans today. Water is an essential ingredient for life as we know it. Such life had plenty of time to evolve in the Martian ocean, as it developed in ours. Moreover, the vast Martian water reserves could not disappear entirely. The planet's southern ice cap alone contains enough frozen water to cover the entire surface of Mars. Every cubic foot of Martian soil contains two pints of water, and groundwater may still flow deep underground. In coming decades, we will probably discover the remnants, and perhaps the continued existence, of microbial life on Mars. That discovery will transform how we understand our place in the universe.

Even without that breakthrough, human exploration and colonization of Mars will be influenced by the history of the planet’s atmosphere, hydrosphere, cryosphere, and perhaps biosphere. The presence of water on Mars will be essential for the survival of future colonists. The historical transformation of Mars from habitable world to frozen wasteland provides a window into what might have been on Earth, and that will encourage scientific missions. The Martian past might even provide a romantic stimulus for a terraforming project that aims to restore the planet to the liveable world it once was.

Hydrocarbon lakes on Saturn's moon Titan, in this false-color image by the Cassini space probe.

New revelations about Mars make clear that relationships between climate change and human activity are no longer be confined to Earth. Other worlds offer additional examples. Venus, the hottest planet in our solar system, provides an instance of a runaway greenhouse effect, a warning for our future that is often cited by advocates for action on climate change. Titan’s complex atmosphere and hydrosphere have yielded seas rich in the building blocks of potentially very alien life. Past, present, and future environmental change on these and other worlds is shaping, and will shape, how we see ourselves. Climate change is influencing our history across the void of space.

~Dagomar Degroot

Author's note: I explore these ideas in greater detail in a journal article that I am preparing for submission.

Source:

Villanueva, G. L., M. J. Mumma, R. E. Novak, H. U. Käufl, P. Hartogh, T. Encrenaz, A. Tokunaga, A. Khayat, and M. D. Smith. "Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs." Science, 2015. DOI: 10.1126/science.aaa3630

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This site explores interdisciplinary research into climate changes past, present, and future. Its articles express my conviction that diverse approaches, methodologies, and findings can yield the most accurate perspectives on complex problems. To contextualize modern warming, for example, we can reconstruct past climate change using models developed by computer scientists; tree rings or ice cores examined by climatologists; and documents interpreted by historians. We gain far more by using these sources in concert than we would by examining each in isolation. Yet we must approach such interdisciplinarity with caution. The problems presented by climate change scepticism provide lessons for academics crossing disciplinary boundaries, and for policymakers, journalists, and laypeople interpreting interdisciplinary findings.

In academia, climate change scepticism is usually interdisciplinary. To attack climate change research, academic sceptics use credibility and, occasionally, scholarly methods accrued in relevant disciplines but often unrelated fields. For example, in the late 1980s and 1990s, eminent physicists William Nierenberg and Fred Seitz were among the most outspoken critics of the global warming hypothesis. According to historians of science Naomi Oreskes and Erik Conway, the scepticism expressed by Nierenberg and Seitz grew, in part, from their belief that the ends of supporting unfettered capitalism justified the means of deliberately distorting scientific evidence (Oreskes and Conway, 190). However, another part – perhaps the most damaging – emerged from the conviction that their disciplinary backgrounds gave them special insight into climate change research

Physicists – including one of our own editors – play a crucial role in modelling and interpreting climate change. Yet not all physicists are alike. Nierenberg was a renowned nuclear physicist who oversaw the development of military and industrial technologies for exploiting the sea. Seitz developed one of the first quantum theories of crystals, and contributed to major innovations in solid-state physics. Owing to their similar academic backgrounds, both Nierenberg and Seitz distrusted the lack of certainty in climate modelling, and both would have despised the occasionally fuzzy probabilities that must accompany climate history. Their scepticism effectively takes the most tenuous elements of climate science and argues that they are not science, because “real scientists” know better.

These attitudes highlight one of the most important but least appreciated aspects of interdisciplinary research: humility. When we step into another field, we step into another culture with characteristics that often have sound reasons for existing. Before challenging assumptions that inform a discipline, we should thoroughly learn the language, methods, and concepts of scholars in that discipline. Only then can we appreciate their findings.

Climate scepticism can also reveal that differences between subfields within academic disciplines can be more significant than distinctions between those disciplines. An environmental historian, for instance, can have much more in common with a climatologist than a postmodern cultural historian. Another example: Fred Singer is an atmospheric physicist who played an important role in developing the first weather satellites. However, he has little respect for the methods or conclusions of mainstream climate research.

In 2006, Singer told the CBC’s The Fifth Estate that “it was warmer a thousand years ago than it is today. Vikings settled Greenland. Is that good or bad? I think it's good.” In an interview with The Daily Telegraph three years later, he acknowledged that “we are certainly putting more carbon dioxide in the atmosphere.” However, he argued that “there is no evidence that this high CO2 is making a detectable difference. It should in principle, however the atmosphere is very complicated and one cannot simply argue that just because CO2 is a greenhouse gas it causes warming.”

Vikings did settle in Greenland, and the atmosphere is very complicated. However, global temperatures are warmer now than they were a millennium ago, and we can certainly trace relationships between modern warming and atmospheric concentrations of CO2. Singer may be an atmospheric physicist, but he is hardly qualified to offer any observations on the state of climate change research.

Global temperature anomalies (redder is warmer) from 2001-2009, relative to the average from 1951-1980. NASA images by Robert Simmon.

Distinctions between different kinds of scientists – and different agendas among scientists – are always worth remembering when exploring the study of climate change. In a recent article, the popular website Reporting Climate Science described a disagreement between physical oceanographer Jochem Marotzke and meteorologist Piers Forster on the one hand, and “climate scientist” Nic Lewis on the other. Marotzke and Forster recently published an article in the journal Nature that confirmed the reliability of climate models for predicting climate change. Lewis accused them of circular reasoning and basic mathematical and statistical errors.

Lewis is, in fact, a retired financier with a degree in mathematics, and a minor in physics, from Cambridge University. Does that make him a climate scientist? He is certainly qualified to challenge mathematical approaches, and he does not deny the basic physics of anthropogenic climate change. For policymakers, journalists, and even scholars in different disciplines, it can be difficult to discern with what authority he speaks.

Similar problems are at work in another recent academic debate. This one unfolded in the pages of the Journal of Interdisciplinary History. As described on this website, two economists took issue with the notion of a “Little Ice Age” between the fourteenth and nineteenth centuries. They waded into an established field – climate history – and assailed one of its most important themes – the existence of a Little Ice Age – without appreciating the methods and findings of recent scholarship.

For example, they used a graph of early modern British grain prices as a direct proxy for contemporary changes in temperature. But those grain prices were influenced by so many human variables that, for modern scholars, they can, at best, suggest only how one society responded to climate change. While attacking the rigour of climate reconstructions, the economists actually introduced data that is far less rigorous than climate historians use today.

Within academia, most instances of climate change scepticism are case studies of interdisciplinary approaches gone wrong. Interdisciplinarity can help us approach thorny issues in new ways, but such work should be collaborative. When adherents of one discipline or field dictate to those in another, the results are usually destructive.

~Dagomar Degroot

Note: the cover photo was taken by our editor, Benoit Lecavalier, during a recent trip to Greenland.

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Last year might have been the hottest year ever recorded by our instruments. Average global temperatures were at least 0.27° C warmer than the average between 1981 and 2010, which was in turn up from the preindustrial norm. Overall, the past 17 years have been very warm, and since 2002 temperatures have been consistently well above the 1981-2010 average. However, that consistency is not clearly reflected in Arctic sea ice trends. In fact, the winter extent of Arctic sea ice has expanded in the last two years, seemingly defying projections of its imminent collapse.

Arctic sea ice is extremely complex and comes in many forms that respond more or less aggressively to seasonal changes and temperature anomalies. Currents, wind patterns, and even subtle differences in Earth’s gravitation also influence sea ice extent, although temperature usually plays a dominant role. As a result, Arctic sea ice coverage rises in winter and falls in summer. Its minimum and maximum yearly extent reflect shifts in average annual temperature, and in turn climate change.

Maximum Arctic sea ice extent in 2010/11. The pink outline denotes the median ice edge between 1979 and 2000.

In the winter of 2010/11, Arctic sea ice reached its lowest-recorded extent (above). Satellite data reveals that, in December 2010, average Arctic sea ice covered just 12 million square kilometers. While that may sound like a lot, it is some 1.35 million square kilometers below the 1979-2000 average, and 270,000 square kilometers below the previous record low (set in 2006).

The sharp decline in Arctic sea ice coincided with very high global temperatures. In fact, scientists are still determining whether 2014 was actually warmer than 2010. In the wake of the winter of 2010/11, it seemed as though even the direst projections of Arctic sea ice decline had been too optimistic. Perhaps a threshold had been crossed, a tipping point had been reached, and Arctic sea ice would soon vanish.

Arctic sea ice extent for December 2014.

However, since the winter 2010/11 Arctic sea ice extent has haltingly recovered. Satellite maps demonstrate that Arctic sea ice currently covers 12.52 million square kilometers, about 520,000 square kilometers more than the 2010/11 maximum (above). The greatest change relative to 2010/11 is in the Canadian Arctic and Subarctic, where the Hudson and Baffin Bays are now completely covered with ice.

If Arctic warming has persisted since 2010, why has Arctic sea ice recovered? One possible explanation lies in the recent history of the Arctic Oscillation (AO), a band of winds that circle the Arctic in a counter clockwise direction. When the AO is in a positive phase, its winds move quickly, tightly sealing frigid air in the Arctic. When it is in a negative phase, its winds move more slowly and the band is distorted, allowing Arctic air to descend towards lower latitudes. There appears to be a correlation between a negative AO and reductions in Arctic sea ice extent. The AO, which was in a strongly negative phase in 2010, is now apparently in a weakly positive setting.

Recent research also suggests that Arctic sea ice has a very low “memory” of previous trends. If, for example, Arctic sea ice extent is very low in September, winter heat loss is high, encouraging the formation of more sea ice. Such processes explain high year-to-year fluctuations in sea ice, yet they do not preclude long-term trends.

Historical sea ice trends (black), model simulations of different emissions reductions (coloured lines). Shaded areas account for error.

The apparent recovery of Arctic Sea Ice therefore does not counter long-term developments in either regional sea ice decline or global warming. Sea ice extent in December was still 540,000 kilometers below the 1981-2010 average, which means that sea ice coverage in the Arctic is still declining by 3.4%/decade. Most model simulations still project an accelerating decline in Arctic sea ice extent, even in optimistic scenarios in which our civilizations sharply reduce their greenhouse gas emissions (above).

Model simulations, scientific proxy data, and documentary evidence assessed by interdisciplinary scholars can contextualize sea ice in the modern Arctic in light of the distant past. My own recent research suggests that sea ice extent in the Arctic north of Europe during December 2014 is not dissimilar to what was encountered by European polar explorers during summer expeditions at the height of the Little Ice Age. This reflects climate change on a remarkable scale, given the vast annual difference between summer and winter sea ice coverage in the Far North.

From: Dagomar Degroot, “Exploring the North in a Changing Climate: The Little Ice Age and the Journals of Henry Hudson, 1607-1611.” Journal of Northern Studies (2015, forthcoming).

For example, I traced sea ice recorded by Henry Hudson and his crew, during their first Arctic expedition. In the above map, the outbound journey is depicted with a black solid line, while the return journey portrayed in a blue, dashed line. The part of the voyage in which ice was sighted is in white; a solid white line for the outbound journey, and a dashed line for the return. Compare the summer sea ice sighted in the Hudson journey with the edge of winter sea ice today (the second map provided in this article).

Ultimately, Arctic sea ice fluctuates from year to year in ways that can temporarily mask gradual climate change. The world is warming, and the Arctic is warming faster than anywhere else. It is important to keep an eye on the recent recovery in Arctic sea ice, but all indications are that it is just a momentary reprieve in a very worrisome trend.

~Dagomar Degroot

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In Europe, the “Bronze Age” lasted nearly 2,000 years, from approximately 3200 BCE to roughly 600 BCE. In this period, bronze tools were forged for the first time, revolutionizing how Europeans manipulated their world and competed for resources. The first trading networks connected the continent, as navigational knowledge reached heights that Europeans would not exceed until the fifteenth century.

Centralized “palace economies” flourished throughout Europe and the Middle East, in ancient civilizations we remember today: on Minoan Crete, in Mycenaean Greece, in the Mesopotamian conquests of the Hittites and Akkadians, and of course in Egypt. Then, in the centuries around 1000 BCE, populations collapsed across Europe and the Middle East, sometimes in remarkably sudden events that must have been even more traumatic than the fall of the Roman Empire. In many regions, small, scattered villages were all that remained of the great Bronze Age civilizations. In Europe, it would be centuries before societies of similar complexity would rise again.

Those who study past climates are drawn to disaster, and not without reason. If we can establish that social crises coincided with periods of abrupt climate change, we can be pretty sure that further investigation will turn up connections between climate and human history. Historians, archaeologists, anthropologists, and scientists often find that connections between climate and human activity are particularly clear, and especially well-documented, in times of crisis. It is no surprise, then, that scholars have sought to link the Bronze Age collapse to climate change.

For example, while surveying 250,000 years of climate history, historian John Brooke of Ohio State University argues in an ambitious new book that the onset of a “cold, dry climate has to be a fundamental explanation of the demise of the Bronze Age of the greater Mediterranean.” (Brooke, 2014) Harvests failed in a changing climate, and subsequent food shortages undermined palace economies while provoking mass migration. Civilizations clashed, populations mingled and therefore spread disease, and piracy spread across the Mediterranean. Other scholars have tied roughly synchronous collapse in Northwestern Europe to changing climatic conditions. (Raftery, 1994; Tipping et al., 2008)

It is a compelling story, especially because it appears to offer a vivid warning for us today. However, like many straightforward narratives that tie climate change to historical collapse, that story is being revised by cutting-edge, interdisciplinary scholarship. In a paper recently published in Proceedings of the National Academy of Sciences, a team of scientists under lead author Ian Armit of the University of Bradford set out to reconstruct the late Bronze Age climate with unprecedented precision. Archaeological activity has surged across Ireland, offering abundant new sources for radiocarbon dating. Altogether, the researchers analyzed 2,023 radiocarbon dates in data from peat bogs and archaeological sites to build their new climate record.

An Irish "crannog" - a defensive structure - from the late Bronze Age. Photo by Christine Westerback.

They found that, in Northwestern Europe, populations began to decline more than a century before the late Bronze Age climate started to cool. Collapse in this part of Europe therefore cannot be tied to climate change. In fact, the authors argue that, all along, social and economic shifts were more than sufficient to explain the fall of regional Bronze Age civilizations. Trading networks and, in turn, stratified civilizations based around bronze production could not survive the advent of the Iron Age, when metals stronger than bronze were suddenly widely accessible.

Not surprisingly, this thesis is not quite as straightforward as the scientists suggest, because in many places people only gradually transitioned from bronze to iron. Nor does the climatic history of Northwestern Europe necessarily translate to southern Europe and the Middle East. Moreover, historians like Brooke have long acknowledged that climate change is but one possible explanation among many for the late Bronze Age collapse.

Ian Armit and his coauthors conclude that, in an age of global warming, “it is easy to view climate as the primary driver of past cultural change,” but “such assumptions need to be critically assessed using high-precision chronologies” that “guard against misleading correlations.” Sometimes historical work could use a little more methodological rigour, and certainly scientists, archaeologists, and historians should be prepared to work together in uncovering the climate history of the distant past.

However, at other times excellent historical work is grounded on cutting-edge scientific data that is revised by later studies. That can undermine some compelling narratives, but that does mean those narratives were never worth telling. Scholarship is a conversation, and that conversation gains depth through daring, provocative stories.

~Dagomar Degroot

Sources:

Armit, Ian et al., “Rapid climate change did not cause population collapse at the end of the European Bronze Age.” PNAS 111:48 (2014): 17045–17049.

Brooke, John L. Climate Change and the Course of Global History: A Rough Journey. Cambridge: Cambridge University Press, 2014.

Raftery, Barry. Pagan Celtic Ireland. The Enigma of the Irish Iron Age. London: Thames and Hudson, 1994.

Tipping, Richard et al., “Response to late Bronze Age climate change of farming communities in north-east Scotland.” Journal of Archaeological Science 35 (2008): 2379–2386.

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Last month, world leaders met at UN Headquarters in New York City for Climate Summit 2014. As protests raged across the globe, diplomats established the framework for a major climate change agreement next year. The aim will be to limit anthropogenic warming to no more than 2 °C, a threshold established by scientists and policymakers, beyond which climate change is increasingly dangerous and unpredictable.

Just days after the 2014 summit, policy expert David Victor and influential astrophysicist Charles Kennel published an article in Nature that called on governments to “ditch the 2 °C warming goal.” Kennel and Victor argue that the rise in average global temperatures has stalled since 1998, as warming is increasingly absorbed by the world’s oceans. Variations in global temperature therefore do not directly reflect climate change, and governments should adopt other benchmarks for action. Atmospheric concentrations of carbon dioxide, they contend, more accurately reveal the relentless advance of climate change. In any case, limiting the rise in global temperatures to just 2 °C would impose unrealistic costs on national economies.

Not surprisingly, responses to Victor and Kennel have been swift and comprehensive. For example, physicist and oceanographer Stefan Rahmstorf argues that short-term temperature variability does not undermine the case for a 2 °C limit, especially when there is little evidence for a “pause” in global warming. He explains how scientists and policymakers selected the limit, and cites studies synthesized by the IPCC, which conclude that holding the rise in planetary temperatures to 2 °C would cost no more than 0.06% of the world’s annual GDP. Kevin Anderson, Deputy Director of the Tyndall Centre for Climate Change Research, claims that Victor and Kennel have confused the roles that should be pursued by scientists in international climate change negotiations. Like Rahmstorf, he maintains that the 2 °C limit is neither misplaced nor unachievable. As a climate change advisor to the British government, he explains that, “the UK, almost overnight, conjured up over £350b to bail out the banks and stimulate the economy – but it has earmarked just £3.8b for its Green investment bank!” Physicist Joe Romm argues that a new study, which finds that scientists may have underestimated the extent of global warming, only strengthens the case for a 2 °C limit. To their credit, Victor and Kennel wrote a lengthy response in the New York Times to these and other critiques.

Global mean surface temperatures creep higher, 1880-2013 (NASA GISS). The mean temperature from 1880-1900 was chosen as the Preindustrial Level. For more, see: http://goo.gl/Z59FH1.

Missing from this debate are perspectives from those who study the past: the ways in which natural climate change has actually influenced human history. This is unfortunate, because historical relationships between climate and society can yield important insights on the usefulness of a 2 °C limit.

Take, for example, the sixteenth and seventeenth centuries, when Europeans entered the Arctic and Subarctic as never before. Journeys of exploration gradually transformed scholarly understandings of the Far North and shaped popular attitudes towards nature and empire. They paved the way for new settlements and laid the groundwork for the exploitation of marine resources that would alter European diets, stimulate the continent’s northern economies, and transform Arctic environments. All this during an early modern “Little Ice Age” that cooled temperatures across the Arctic and Subarctic by at least 0.5 °C, relative to the twentieth-century norm.

This apparent paradox is a focus of my recent research. I have learned that it can be tempting to assume that global cooling or warming will have straightforward impacts at the regional or local level, but such assumptions are often wrong. It often feels as though climate history is the study of bewildering, sometimes infuriating complexity. I frequently find myself using eclectic sources to trace, for example, how changes in solar radiation altered global temperatures, regional cyclonic activity, a series of storms above a town, damage sustained in that town, and how people understood what was going on. This is a part of what makes climate historians so useful to the broader historical discipline: we are always coming up with new ways of understanding how the local reflects the global, of discerning how – and why - things change over time.

Lately, I have used cutting-edge scientific data to reinterpret journals written by Arctic and Subarctic explorers in the sixteenth and seventeenth centuries. I discovered that some expeditions to the Far North benefitted from unusually warm ocean currents and hot summers that actually reflected counter-intuitive links between local environments and the globally cool Little Ice Age.

I have also started to investigate the seventeenth-century rise of the Dutch and English whaling industry around the island of Spitsbergen in the seas north of Norway. It might seem obvious that Arctic whaling expeditions would suffer in colder decades, and indeed the pack ice between Spitsbergen and Greenland would expand as regional temperatures cooled. However, at the same time bowhead whales prized by hunters would congregate near the pack ice, which made them much easier to hunt. The whaling industry therefore enjoyed its best years during the coldest phases of the Little Ice Age.

In other words, my research has revealed that when our focus is strictly on warming or cooling trends, we can lose sight of how climatic shifts actually affect people.

Dutch whalers at Spitsbergen in the seventeenth century. Bowhead whales were actually easier to kill in cold years, when they would congregate near the pack ice.

Still, interdisciplinary scholars of past climates trace climate change by reconstructing variations in average temperature. We classify our climatic past according to these swings in average temperature, and how they influenced the advance and retreat of glaciers. Hence our (little) ice ages and warm periods, our minima, maxima, and anomalies. Archeologists, historians, and scientists of many stripes then investigate how humans and animals responded to particularly warm or cold periods. Of course, many continue to dig deeper, considering diverse weather patterns and reaching sometimes-surprising conclusions. Nevertheless, our initial focus on average temperatures usually shapes the kinds of questions we can ask.

Does that mean we miss the mark? Should we stop assuming that climate change and average temperature change are one and the same?

Perhaps not. In reconstructing past climates, scholars of past climates often find that while changes in average temperature do not tell the whole story, they can and should tell us where to start looking. Average temperatures are closely linked to changes in the solar energy earth receives and absorbs, which ultimately drives the environmental changes that reflect climate change. Shifts in regional precipitation, wind dynamics, or ice cover therefore usually respond to shifts in average regional temperature, which are closely correlated to fluctuations in average global temperature.

In that light, the 2 °C limit makes a lot of sense. A focus on average temperature might miss some of the complexity of climate change and its possible ramifications for our future, but changes in temperature are closely linked to the kinds of environmental conditions that Victor and Kennel would rather track separately.

Moreover, nuance is less important in climate change mitigation than it is for climate change adaptation. Greenhouse gas emissions need to decrease because temperatures can only increase so much before they imperil our civilization. The mechanisms and technologies for limiting emissions exist today; now is the time to implement them, rather than adjust our acceptable thresholds.

After all, the human history of past climate change also provides a warning. During the Little Ice Age, a moderate decline in average temperatures profoundly and often disastrously affected societies around the world. What will unprecedented warming do to us?

~Dagomar Degroot

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Contributing Author: Benoit S. Lecavalier

Permanent twilight and the northern lights during a night watch.

The Greenland ice sheet is melting fast, and it contains enough water to raise global sea levels by over seven meters if it were to disappear entirely. However, thousands of years ago the ice sheet was much larger, with a total of 12 metres ice-equivalent sea-level. There are many questions that remain unanswered about how Greenland lost all this ice from past to present. For example: how and where did the Greenland ice sheet lose mass? What climate history resulted in such a drastic change in the ice sheet? This summer, these were the questions that led a multidisciplinary team of geologists, geophysicists, biologists, and biogeologists to Southeast Greenland. We were embarking on an expedition to better understand its climate history, and so resolve part of a much bigger story.

We were going to the Arctic by ship to take advantage of the best weather it had to offer for the summer 2014 field season. As we waited in Reykjavik with our equipment, our ship - the last sailing vessel built of wood with ice plating for navigating Arctic waters - was traveling from Denmark to Iceland. It was called the Activ, and it was an old-fashioned schooner with three masts and fourteen sails. On the way to its destination, the ship had to cross the rough waters of the Denmark Strait, where we had to endure three days of seasickness.

The Activ.

Fog descended upon the ship as we approached the Greenlandic coast. The ship navigated carefully past icebergs in search of shallow water to anchor for the evening. There was little room for error: in emergencies we depended entirely on satellite phones, and even by helicopter we were hours from the nearest town. Finally, we sailed into a fjord and found a proper place to anchor, before preparing the inflatable motor boats that would ferry us to and from our research sites.

The fjords along the coast were carved over thousands of years by the expansion and retreat of the ice sheet. Because they were flooded by the sea when the ice retreated, for us they were a valuable inlet to the Greenlandic interior. We got there by motor boat, hoping to collect rock samples for cosmogenic dating. As the ice sheet receded, boulders were no longer covered by ice that had shielded them from bombardment by cosmic rays. When these particles from space blasted into the rock, specific isotopes were produced in the minerals (Beryllium-10; 10Be), and as time passed they accumulated. Today, scientists can determine how long the rock has been ice-free by measuring the quantity of Beryllium in a sample. In that way, they can infer the position of the ice sheet at a given time.

Helicopter ride over the ice sheet.

At the end of the day, the motorboat was always weighed down by numerous samples, and the commute back to the ship was always long. On our return, we would weave between newly calved icebergs, often passing seals and birds, before finally arriving back home to the ship, with warm food waiting for us. After dinner, decisions were made on where to head next. With the anchor raised, the goal was usually to sail southward through the night. Night shifts were assigned so that there were always two iceberg watchers at the bow of the ship and two people on the bridge concerned with steering. At this latitude and time of year the sun barely dips below the horizon, resulting in a state of permanent twilight. On a foggy night we had to be ready in a moment’s notice to call out an iceberg, while on a clear night we could enjoy the peaceful tranquility of water and wind flowing past the ship.

Collecting cosmogenic samples.

By early August we anchored in a bay within a major fjord in southern Greenland, with the intention of collecting samples for several days. Using the motorboat we traveled near an isolation basin, a lake that had once been connected to the ocean. Thousands of years ago, the ice sheet extended farther at the margins. The weight of the ice deformed the Earth, depressing the crust lower than it presently lies. As the ice receded, the crust rebounded, which disconnected some basins at the coast from the ocean and created new lakes. We collected cores of the sediments at the bottom of these lakes, since they document the microfossil remains of organisms (foraminifera) that inhabited the area. By dating the transition from saltwater to freshwater organisms, we discovered when the basin was separated from the ocean. Given the current elevation of the lake and time of isolation, we acquired an inference for past sea level.

One morning, at the break of dawn, the water was calm yet we heard splashing by the side of the boat. A few minutes later, we left the galley and went up on deck for a day’s work. Suddenly, we noticed that the motor craft was torn and deflated with the emergency kit missing (it had included flares and chocolate, among other things). A polar bear was on the coast tearing through the kit. As we watched, the bear decided he wanted more. He dove back into the frigid water and swam towards us. In a panic we lifted the motor boats, loaded some rifles and carefully watched the bear try to get on board. The bear circled the boat again and again, like a shark. He was attempting to grab on a ridge along the boat when we decided to fire some warning shots. The polar bear quickly fled to the coast where he would remain all day, preventing us from going out and taking more samples.

Polar bear looking for a meal.

The days passed, we collected more samples, and we continued southward into Prince Christian Sound – a fjord complex that separates the mainland from the southernmost tip of Greenland. As we neared the end of our expedition, we finally began to encounter small isolated coastal communities. We sailed from village to village, from Augpilagtoq to Nanortalik, and then to Qaqortoq, where we officially disembarked. We helicoptered to Narsarsuaq where we said goodbye to Greenland, its vast, pristine landscape, its mountains and wildlife, and its ice. We disbanded and flew our separate ways, where new challenges awaited us. Only upon returning to our respective institutions could we begin to interpret the samples we had collected.

The samples will become data, and the data will implemented in models. It is a long process which will ultimately improve how ice sheet models behave. The models must accurately simulate ice retreat to remain consistent with cosmogenic dates. They must unload adequate amounts of ice for the Earth to deform and sea level to change, to coincide with the observations from isolation basins. This procedure will retune and calibrate Greenland ice sheet models, revise their simulations of climate forcing, and increase our level of confidence in our model predictions. It began on a ship navigating never-before sampled areas of Greenland, and it ends as ones and zeros on a super computer. The aim: to better understand how the Greenland ice sheet responded to past climate change, to better predict how it might respond to a warmer future.

More photographs from the Arctic:

The team:

Scientists:

Nicolaj Larsen
Kurt Kjær
Antony Long
Svend Funder
Benoit Lecavalier
Anders Bjørk
Kristian Kjeldsen
Peter Ilsøe
Laura Levy
Anne-Katrine Faber
Sarah Woodroffe
Willi Winrebe
Johan Spens
Micaela Hellstrom

Crew:

Jonas Bergsøe (Captain)
Jeppe Møhl
Gonzalo Guarda
Birk Jessing
Aase Huggler
Fram
Arwyn P.

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One of those brilliant Toronto sunsets

Note: originally posted on The Otter, blog of the Network in Canadian History and Environment.

Like the research that inspired it, this article is a cultural consequence of climate change.

Seven years ago, I was on a bus, reading a book about ancient climates. I looked out the window at a sunset so brilliant, it seemed to ignite Toronto's skyscrapers. I thought of global warming, and wondered: had anyone searched for connections between human history and climate change? Over the next seven years I found out that they had, but that there was still plenty of room for a new perspective.

The book I was reading was the product of an academic culture increasingly affected by the growing manifestations of global warming. Years ago, its importance to me was shaped by my place among a tangle of different cultures that all included discourses about climate change. The sunset that helped me imagine new connections between ideas triggered by these cultures led to a dissertation, which explored the climate history of the Dutch Golden Age. Now completed, the dissertation reveals, in part, that culture is inextricable from the material influence of climate change.

Simply put: we cannot comprehend the human consequences of climate change, past, present, and future, without understanding culture.

That insight was central to the papers of my panel at the World Congress of Environmental History, which recently concluded in beautiful Guimarães, Portugal. Panelists discussed how climate change can upend delicate relationships between humans and local environments, in ways that ultimately influence culture.

Thanks to funding generously provided by the Network in Canadian History and Environment, I was there to chart the ways in which a cooler early modern climate, known as the “Little Ice Age,” influenced the famous Dutch culture of the seventeenth century. My paper drew both from the last chapter of my dissertation, and from my more recent articles on Arctic environmental history.

Moonrise over Guimarães, Portugal, site of the 2014 WCEH.

Strangely, projected relationships between climate and culture rarely feature in the reports regularly published by the Intergovernmental Panel on Climate Change or the World Meteorological Organization. Moreover, scholars of past climates who consider cultural consequences have too often assumed that a worsening climate inspired melancholic cultural responses. Those narratives are easily dismissed by cultural historians who can readily find alternative explanations for changing artistic tastes, or shifting patterns of gendered persecution, during even the coldest decades of the Little Ice Age.

Because the Dutch Republic flourished during the nadir of the Little Ice Age, examining its richly documented culture provides a rare opportunity to refine narratives that connect climate change to culture. My paper argued that literate Dutch observers, writing within a maritime culture that produced detailed records of daily weather, discerned changes in prevailing patterns of extreme weather in the seventeenth century. This partial understanding of climate change might have informed cultural responses, but I believe that we must be careful in making these connections.

Arguably the most famous Dutch “winter landscape.” Pieter Bruegel, the Elder, “Hunters in the Snow,” 1565.

Take the famous Dutch “winter landscapes” of the sixteenth and seventeenth centuries. The rise of these paintings during the onset of a particularly cold phase of the Little Ice Age appears, at first, like an especially direct cultural consequence of climate change. Certainly many scholars of past climates have argued as much. However, on closer inspection, connections between climate and culture are not so straightforward. The painters of winter landscapes often painted indoors, during years that were not especially cold, and their paintings were often heavy with mythology and allegory. Certainly they did not directly reflect contemporary weather or climate. Moreover, winter landscapes were often part of a series, which included depictions of other seasons. Finally, they were attuned to a market that had dried up by the late seventeenth century, another period of extreme cold that was nevertheless not accompanied by paintings of winter landscapes.

The Dutch example therefore reveals that, in order to link climate change to cultural responses, we must carefully establish relationships between climate, weather, individuals, markets, and more. Scholars who examine the human consequences of climate change must range across so many disciplines that making assumptions can be very tempting. However, too easily connecting climate to culture can undermine other conclusions founded on more sturdy ground.

Ultimately, there were some elements of Dutch Golden Age culture that probably reflected the influence of climate change. Among them: poems and illustrations that responded to distinct weather events rendered more frequent during the coldest (or warmest) decades of the Little Ice Age. Technologies like new heating devices and “ice wagons” that travelled speedily across the ice likely also reflected the cultural influence of a cooler climate. So too did the uniquely egalitarian cultures that emerged from winter carnivals, which were held on ice that was more extensive and lasted longer in the chilliest phases of the Little Ice Age.

Overall, concrete cultural responses to climate change in the Dutch Republic were consequences of, or contributed to, the broader societal resilience of the Dutch to the Little Ice Age. At the WCEH, my paper and panel demonstrated once again that relationships between climate change and humanity are inexplicable without a rigorous analysis of culture.

~Dagomar Degroot

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In order to keep global warming below 2° C, there is desperate need for urgency in curbing greenhouse gas emissions. However, national and international policymakers have yet to take action on the scale that would prevent catastrophe. In the most recent issue of Nature Climate Change, Cambridge University geographer David Christian Rose explains why even the governments that have publicly acknowledged the threat of climate change have been so slow to address it. He then introduces practical ways for researchers to communicate more effectively to policymakers.

Most scholars understandably assume that policy should respond to the weight of evidence. To them, influencing policy is simply a matter of articulating abundant evidence with clarity. However, Rose argues that evidence derived from “scientific rationality” is just one factor among the many that influence policy. Rose draws on principles developed by political scientist John Kingdon, who holds that even ideas backed by the best scientific evidence do not become policy unless they fit prevailing political conditions.

To Rose, nothing is more misguided than the continued focus on producing better evidence, undertaken most famously by the Intergovernmental Panel on Climate Change (IPCC). Increasing the certainly of anthropogenic change from 90% (in the IPCC’s fourth report), to 95% (in its fifth), does not account for the ways in which policy is actually formulated.

Rose argues that, in climate change negotiations, progress is rarely impeded by a lack of sufficiently reliable evidence. Instead, Rose claims that talks break down because of questions such as: “Who wins? Who loses? Who decides?” Scientists and other scholars should therefore figure out how their evidence can be presented to policymakers in ways that give it maximum leverage alongside other influences.

Scientists and other climate researchers have a tendency to advertise the peril of inaction. Their frequently apocalyptic narratives are both evidence-based, and intended to galvanize policymakers and the public into action. However, Rose finds that telling “good news stories” can be much more effective, because policy is rarely agreed upon without concrete evidence that it will work. By better communicating these stories, academics and activists alike can demonstrate that adaptation is both possible, and applicable in policy.

Finally, Rose argues that climate change policy recommendations presented by scientists should be attached to issues that are political winners. As an example, he explains that European researchers campaigning against the trade in wild birds were only able to influence policy when they tied the issue to the spread of bird flu. Given the other political influences faced by policymakers, animal welfare was a political non-starter, but public health was not.

Ultimately, the guidelines presented by Rose will strike many academics as cynical recommendations that threaten to turn scientists into lobbyists. Academics, they might claim, should have an unimpeachable voice precisely because they do not employ the tactics used, for example, by big oil lobbyists. Some activists may hold that the inability of political systems to respond directly to evidence is, if left unaltered, a long-term threat to meaningful environmentalism.

However, we do not live in a world where these lofty ideals can always yield practical, short-term solutions of the kind necessary to mitigate, and adapt to, global warming. Rose therefore presents a convincing case: if researchers want policymakers to take action, they should start thinking like policymakers.

~Dagomar Degroot

David Christian Rose, "Five ways to enhance the impact of climate science." Nature Climate CHange 4 (2014): 522-524.

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Many articles on this site outline the indispensable role of documentary evidence for testing, refining, and expanding reconstructions of past climates developed using scientific “proxy” sources and computer simulations. Documents that record past weather were written in literate societies, and are only useful in bulk. Hence, reconstructions of ancient climates cannot benefit from documentary refinement, and the same holds true for reconstructions of regions settled by non-literate societies. Nor are all documents equal: written sources that describe processes that respond to weather are useful, but only those are directly refer to weather can be reliably used to reconstruct past climate change and its influence on human activity.

Unfortunately, the importance of documentary evidence for climate change research can politicize its preservation. This website has conveyed the warnings of government scientists in Canada, who, while muzzled by new government regulations, nevertheless communicated the destruction of essential weather records. Even documentary collections that appear secure are not always adequately categorized, or easily accessible, in government archives.

Recent developments have shown that institutions and scholars are not powerless in the face of these developments. Environmental historian Alan MacEachern of the University of Western Ontario has been instrumental in negotiating a long-term loan in which documentary sources from Library and Archives Canada will be housed at Western Archives. The loan includes some 1,000 boxes containing priceless weather observations, and a further 250 volumes of correspondence, journals, and observations, all written across Canada from 1840 to 1960.

In the 120 years covered by these sources, the world emerged from the Little Ice Age and experienced the first onset of anthropogenic warming. Meanwhile, the Canadian government established what is today known as the Meteorological Service of Canada. This essential social and environmental history will now be preserved, digitized, and widely shared from the security of Western University.

Western University will benefit significantly by housing this collection. The university’s history department is already the home of NiCHE, the influential Network in Canadian History and Environment, and these documents will further establish Western as a hub for environmental history in North America. In particular, they are contributing to the rise of Western as a leading centre for the cutting-edge study of interactions between past climates and peoples. Western recently supported a climate history workshop dedicated to the analysis of these documents, and this autumn it will offer one of the only climate history courses available in Canada. According to MacEachern, who also serves as director of NiCHE, “the arrival of this collection will not only be a great boon to climatologists and historians at Western but it will also make Western a destination for climate history researchers from across Canada and beyond.”

A page from one of the daily observation records now housed at Western.

Can the Western loan serve as a template for the preservation by universities of government records relevant to past climate change? Admittedly, the circumstances surrounding this loan may be unique. However, the scholars and archivists who made it possible have demonstrated that researchers can do more than simply lament the plight of the sources that enable our work.

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Photo Credit: David Cheskin/PA

According to the most recent summary for policymakers published by the Intergovernmental Panel on Climate Change (IPCC), “climate change can indirectly increase risks of violent conflicts” by exacerbating the socially destabilizing influence of poverty and economic shocks. While the IPCC attaches “medium confidence” to this claim, it is hardly controversial. Similar conclusions were made in the IPCC’s 2007 assessment reports. Since then, several studies have established that warfare is correlated to climatic stress, although their methods ignore social and cultural contexts. Many of the world’s most advanced militaries are now at the forefront of state adaptation to global warming. The American military, for example, is not only curbing its greenhouse emissions, but is also actively preparing for conflict stimulated by future climate change.

But how is the conduct of war – not just its origins – actually influenced by climate change? In the latest issue of the journal Environment and History, I published an article that explores this question. In the seventeenth century, three wars between England and the Dutch Republic – then the leading maritime powers of their day – were fought during the onset of an especially chilly stretch of the Little Ice Age in Europe. In my article, I argue that the weather that accompanied the coming of this “Maunder Minimum” affected military operations during the wars in complex and often counter-intuitive ways.

Dutch and English fleets clash in the final battle of the First Anglo-Dutch War. Jan Abrahamszoon Beerstraten, “Slag bij Ter Heijde,” 1653-1666,

The First Anglo-Dutch War, contested between 1652 and 1654, actually preceded the cooling of the Maunder Minimum. I used ship logbooks, correspondence, intelligence reports, and diary entries written during the war to demonstrate that frequent westerly winds can be associated with warmer temperatures during the early 1650s. That usually allowed English fleets sailing from the west to claim the “weather gage,” the windward position from the enemy that, in naval combat, granted initiative in attack and, occasionally, retreat.

The English navy had developed revolutionary tactics in which ships of great size would bombard enemy hulls while sailing past them in line formation. By contrast, Dutch tactics still mandated grappling, boarding, and firing at enemy rigging (ironic, since a Dutch admiral had first debuted “line of battle” tactics some 15 years earlier). English tactics required favourable winds, and English fleets got them in the first Anglo-Dutch War. The Dutch Republic was rich enough to survive several naval reversals, and its shipyards productive enough to stave off defeat. However, on the balance the First Anglo-Dutch War was far more costly for the Dutch than it was for the English.

Human and environmental structures had shifted by the onset of the Second Anglo-Dutch War in 1664. Seasonal temperatures were more variable but generally cooler, storms had become more frequent and more severe, and easterly winds had grown more common. Meanwhile, the Dutch had adopted many of the most effective elements of the English naval system. Dutch fleets sailing to battle from the east now did so with the weather gage, and they were often victorious. Moreover, because English vessels had three tiers of guns while the Dutch only had two, many English guns were located near the water, and had to be retracted in high winds that were more common in a cooler climate. Easterly winds also allowed the Dutch fleet to raid up the Medway River in 1667, forcing the English crown into a peace that clearly benefitted the Dutch.

Dutch ships capture an English flagship during the Second Anglo-Dutch War. Willem van de Velde the Younger, “The Capture of the Royal Prince,” 1666.

In the Third Anglo-Dutch War, the climate of the Maunder Minimum manifested in weather that was defined less by easterly winds than incessant storminess. This time, the Dutch Republic was invaded by French and German armies while besieged at sea by a united Anglo-French fleet. However, in the summer of 1672 relentless gales kept the allied fleet from supporting a naval invasion, just as the Dutch fleet was partially disbanded so its soldiers and artillery could defend against invasion on land. Thereafter, Dutch admiral Michiel de Ruyter conducted a remarkably successful guerrilla campaign, aided by frequent easterly winds. The Dutch Republic survived its greatest crisis of the seventeenth century, and England signed another concessionary peace in 1674.

So, what does this seventeenth-century story tell us about war and climate change today?

First, it demonstrates again that climate change is mediated by human decisions, institutions, and cultures. The Dutch Admiralties might not have prevailed in the second and third wars had they not learned from the success of the English, who might have won the third war were it not for the leadership of De Ruyter. Second, the article reveals that military operations are influenced by short-term weather, which is often but certainly not inevitably affected by long-term climate change. The distinction is important, because the weather that most influences a battle can actually be an exception to the climatic trend.

Ultimately, far more studies are required that explore not only how climate change contributes to the cause of war, but also how it shapes wars once they begin.

~Dagomar Degroot

Note: this article is a greatly condensed version of dissertation chapters that also examine how climate influenced weather that affected shipbuilding, marine intelligence networks, privateering, and warfare on land during the Anglo-Dutch Wars.

Dagomar Degroot, “‘Never such weather known in these seas:’ Climatic Fluctuations and the Anglo-Dutch Wars of the Seventeenth Century, 1652–1674.” Environment and History 20:2 (May 2014): 239-273.

United States Department of Defense, Quadrennial Defense Review Report. February 2010.

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The Little Ice Age (LIA) was a period of generally cooler, and more variable, temperatures that was felt across most of the globe from the thirteenth to the nineteenth centuries. In the wake of a very cold winter in North America, and a very wet winter in Britain, it has been all over the news lately. For example, in the April issue of Foreign Affairs, Deborah Coen evaluates a major new study on the Little Ice Age by fellow historian Geoffrey Parker. In the March 23rd New York Times Sunday Review, Parker presents his “lessons from the Little Ice Age.” Two days earlier, novelist Sarah Dunant offered some of her own lessons from the period for BBC News Magazine.

The focus of each piece is the frigid seventeenth-century nadir of the LIA. For Parker and Dunant, the conclusion is simple: the LIA was disastrous for all who experienced it. Global suffering during a cooler climate foreshadowed what we can expect in a hotter world. If we wish to avoid that fate, we had better act now.

This is an important message, and it comes almost exactly one week before the release of a critical report by the second working group of the Intergovernmental Panel on Climate Change. That already controversial report will outline how projected global warming will influence our societies. Its conclusions are expected to broadly mirror those of an earlier 2007 assessment: massive changes are in store for our species, and we had better prepare for what we can’t avoid. Although compiled with very few contributions by historians, the report will therefore echo the message released by Dunant and Parker.

In its reports, the IPCC is keen to interrogate its results and admit areas of relative uncertainty. Moreover, Parker rightly identifies a “fatal synergy of weather, wars and rebellions” in seventeenth-century Europe. Dunant, relying heavily on Parker’s conclusions, explains that climate did not cause contemporary crisis, but it was “a powerful trigger” (which begs the question: what is the difference between cause and trigger?).

The death of Gustavus Adolphus during the Thirty Years' War, 1632. Carl Wahlbom, The Battle of Lützen, 1855.

However, there is a streak of climate determinism to the warnings framed by the calamity of the LIA. To Parker, climate change exacerbated the catastrophes of the seventeenth century, causing famines and wars so severe that the height of French soldiers, influenced by childhood nutrition, declined by an inch. Dunant similarly explains that, when “life became unbearable” after a few failed harvests, Europe experienced revolts, revolutions, and its infamous early modern witch hunts. Altogether, a third of the world’s population perished. If seventeenth-century cooling killed millions, Parker asks, might global warming kill billions?

Parker is one of the world’s most influential historians. His refinement of the concept of a sixteenth and seventeenth-century “military revolution” was pivotal in the development of modern American military strategy in the Middle East. He is one of the few proponents of huge concepts in history who is also a very fine historian, and accordingly I have taught his ideas to my students. He has become one of the foremost advocates for climate history and indeed for the role of historians in climate research. His attempts to link the influence of the LIA to a global crisis also offer a compelling case for urgent action in the face of anthropogenic climate change.

However, for five years I have conducted research that challenges the idea that simple links connected past climate change and social crisis. By studying the seventeenth-century Golden Age of the Dutch Republic, I have demonstrated that some societies could flourish even during a cold and, in the North Sea region, stormy climate. Paintings by Dutch masters like Rembrandt and Vermeer were the cultural expressions of a capitalist trading economy that prospered during the seventeenth century. The changed wind patterns that accompanied the chilliest years of the LIA actually provided advantages for Dutch war fleets and merchant ships alike. Watery transportation networks froze in cold winters, but Dutch citizens used sleds and skates to maintain their freedom of movement.

Noted climatologist Jean Grove has argued that “the impact of climatic changes on human society depends upon their scale on the one hand and the characteristics and sensitivity of the society concerned on the other.” In other words, during moderate climate change – and the Little Ice Age was not a major glaciation – the actions and social structures of human beings shape the expression of environmental stimulus. That was why the remarkably advanced commercial economy of the Dutch Republic responded differently to climatic stress than agricultural economies elsewhere in Europe.

The Dutch in the Little Ice Age. Hendrick Avercamp, Winterlandschap met ijsvermaak, 1608.

Moreover, even in its nadir the LIA was not universally cold. Interdisciplinary reconstructions of past climates suggest that the middle of the seventeenth century was actually warmer than the beginning or end. Hot summers and mild winters interrupted even some of the chilliest decades of the LIA, and cold conditions were never perfectly synchronized across the globe.

It is dangerous to say that climate change starts wars, causes famines, and ultimately kills people. First, these claims are often inflated. For example, European populations stagnated in the seventeenth century, but they were certainly not slashed by a third (which would be equivalent to the devastation caused by the Black Death). Nor is there any evidence for a global demographic catastrophe on that scale.

Second, such claims rip the agency and, in turn, the culpability from human actors. Historians know better than most that big economic or environmental structures are ultimately leveraged by people making decisions. Resource shortages can cause wars, but can also encourage the development of new, and occasionally more equitable, social structures. There is no inevitable response to environmental crisis, and this is perhaps the most valuable lesson we can learn from the Little Ice Age.

It is therefore better to think of climate change as one influence among the many that stimulate and mitigate societal crises. The influence of climate change becomes more direct as it becomes more severe, but its effect on society is still channeled by human beings. Here, then, is an alternative way of framing today’s climate crisis in light of the past:

Global warming is alarming precisely because humanity has not experienced a climatic transition of this potential magnitude since our ancestors hunted mammoths across the tundra. Our plight is frightening not because it has historical parallels, but because it has none. Our best historical information suggests that the negative effects of moderate climate change will be most felt by those who are already vulnerable. However, the severe climate change we will likely experience will be felt by everyone. The need for a shift away from fossil fuels has never been more urgent.

~Dagomar Degroot

Note: these themes are further discussed in the conclusion of my dissertation, The Frigid Golden Age: Experiencing Climate Change in the Dutch Republic, 1560-1720.

Grove, Jean M. Little Ice Ages: Ancient and Modern. London: Routledge, 2004.

Parker, Geoffrey. Global Crisis: War, Climate Change and Catastrophe in the Seventeenth Century. London: Yale University Press, 2013.

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Last year the World Meteorological Organization released an important summary report on the world’s climate and how we make sense of it. The World’s Climate: 2001-2010 was unfortunately overshadowed by the publication of the Fifth Summary for Policymakers written by the UN’s Intergovernmental Panel on Climate Change. However, its conclusions are continuing to trickle through blogs and media outlets, as they shed new light on the past, present, and future of the world’s climate. Some of these conclusions will be familiar to scientists, but they are worth repeating for scholars of different disciplines, policymakers, and the general public. Among them:

1. There is no “pause” in global warming.

According to the science summarized by the WMO, the decade between 2001 and 2010 was the warmest since the beginning of reliable instrumental measurements (ca. 1850). Average global temperatures in that decade were 0.47° C higher than they were between 1961 and 1990, and 0.88° C higher than they were from 1901 to 1910. Between 2001 and 2010, nine years were among the ten warmest ever recorded. The last year of the decade, 2010, was also the hottest ever recorded, and nowhere was heating more pronounced than in Greenland. Indeed warming was particularly severe across the entire northern hemisphere, especially on land, which was 0.79° C hotter than the 1961-90 average.

Decadal changes in combined average sea and land surface temperatures. World Meteorological Organization, 2013.

2. The world is continuing to warm despite variability in natural climatic trends.

From 2001 to 2010, the world did not experience a major El Niño event, a natural warming of the equatorial Pacific Ocean that raises global temperatures. Instead, strong La Niña events marked by a natural cooling of the same waters prevailed in 2008 and even 2010. Weak La Niña events, or neutral conditions, accompanied most other years. Meanwhile, the North Atlantic Oscillation and the Arctic Oscillation, linked regions of high atmospheric pressure, switched into their “negative” phase in 2009-10. This chilled winter temperatures across northern and central Europe.

However, the steady increase of atmospheric greenhouse gases in this decade overwhelmed the cooling influence of natural climatic signals. Carbon Dioxide, which has now risen by 39% since preindustrial times, increased to 380 parts per million (ppm), from 361.5 ppm in the previous decade. Methane, which has risen by a whopping 158% since the preindustrial era, rose from 1,758 to 1,790 parts per billion (ppb). The wholesale transformation of the world’s atmosphere is well underway, and it is changing weather now. Speaking of which:

3. Linking climate change to extreme weather is difficult, but the evidence is overwhelming.

Historical climatologists struggle with this all the time: how can we link a local weather event that transpires over hours, or days, to a gradual climatic trend? Even when supercomputers are involved, there are no easy answers. Instead, we must rely on probability, and when we do we discover that the evidence can be very persuasive. The same holds true in our study of the present and the future. According to the WMO, 56 countries reported their highest absolute daily maximum temperature record from 1961 to 2010 in the most recent decade. Only 14 countries reported their absolute daily minimum temperature in that period. Dramatic heat waves, like the one in the summer of 2010 that contributed to 55,000 deaths in Russia, were very likely triggered or worsened by the influence of anthropogenic climate change.

Moreover, warm air can hold more moisture, and higher temperatures can speed up the hydrological cycle. Therefore climate change has probably contributed to the higher frequency, and increased severity, of extreme precipitation events. Globally the first decade of the twenty-first century was also among the wettest on record, and 2010 was the wettest year ever recorded. In the decade floods were the extreme weather-related event that was most frequently experienced around the world.

Major tropical storms in the western hemisphere, 2001-2010. World Meteorological Organization, 2013.

Scientists also found that 2001-10 was accompanied by the most tropical cyclones ever recorded in the North Atlantic Basin. The 1981-2010 long-term average of 12 named storms per year was exceeded by three storms. In 2005 there were no fewer than 27 storms – a record – of which seven were classified as major hurricanes (including hurricane Katrina). However, the average or below-average cyclonic activity in other regions reveals that we must be cautious when linking major storms to a hotter climate. The great human and infrastructural damage inflicted by storms can as often reflect intensified human activity as the effect of climate change.

Ultimately:

The WMO study is the latest major report that employs research into past climates to demonstrate the scale of global warming and undermine the “pause” hypothesis. It goes without saying that dramatic action is needed soon, but it should also be noted that further study of the past can contribute to that action. The better we understand our plight, the better we can confront it.

Source: The Global Climate 2001-2010, A Decade of Climate Extremes – Summary Report. Geneva: World Meteorological Organization, 2013.

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Initially published on ActiveHistory.ca

In Toronto, 2013 was a year of storms. The media storm kindled by the mayor’s chicanery was twice interrupted by meteorological storms that threatened lives and property on an unprecedented scale. On July 8th more than 100 mm of rain inundated the city in a matter of hours, triggering flash floods that caused more than $1 billion in property damage. Three days before Christmas, winter storm Gemini unleashed more freezing rain than was ever recorded in Toronto. Some 300,000 customers – representing perhaps one million people – lost power as temperatures plummeted below -10° C. This time the city’s infrastructure succumbed to the force of frozen water, and those desperate for heat too often turned to candles, generators, and other sources of deadly carbon monoxide. I am a climate historian living in Toronto. Experiencing these storms helped me better understand how climate change, weather and society influence each other in the past, present, and future.

Climate historians or “historical climatologists” reconstruct past weather and climate using some combination of computer simulations, evidence from the natural world, and documentary sources. The field is interdisciplinary, and many of its scientists stop at these climate reconstructions. However, most of its historians also explore relationships between climate change, weather, and human history. As I have described in previous Active History articles, I am one of those historians. My research explores the social influence of the “Little Ice Age,” a roughly 1° C cooling of global temperatures between the thirteenth and nineteenth centuries. I hope that such research will give us insight into relationships between climate change and society in a warmer future.

Climate historians and climatologists both wrestle with the complexity of linking weather to climate change. Many days of supercomputer calculations are necessary to trace all the distinct environmental connections that link atmospheric trends to atmospheric events. What we know for sure, however, is that some events grow more common in different climates. In the North Sea region, severe gales were more frequent during the coldest phases of the Little Ice Age. Similarly, storms like those that afflicted Toronto last year will become more common as our climate warms in the coming century.

I was foolish enough to walk through the city in the immediate aftermath of both disasters. On July 8th I embarked on an hour-long walk just after writing a dissertation chapter that investigated heavy rainfall in the seventeenth century. It was time to experience what I studied. As I started my expedition the rain had diminished, yet flooding continued unabated. I waded through bubbling brooks that flowed across what had been concrete hours before. Cars sloshed by, rolling forwards just faster than I could walk, as commuters huddled in subway stations and sirens wailed in the distance.

Far more alarming was the morning of December 23rd. Once again I ventured from my apartment in the final hours of a storm, this time to secure food, warmth, and electricity. A final drizzle of freezing rain added to a ubiquitous layer of ice that already seemed at least two centimeters thick. Above me, trees groaned and creaked under the weight, and power line after power line lay draped across the sidewalk. Suddenly, a colossal crash: I turned to see that a huge tree had fallen nearby. A policeman at another collapsed tree rushed to respond, and I awkwardly staggered in pursuit across the ice. When I approached I saw that a van and a jeep had been torn apart. The rest of my walk was much more cautious.

Destruction in the Annex, December 23rd, 2013. Photo credit: Dagomar Degroot.

For me, both strolls through my storm-altered urban backyard highlighted the complex psychological effects of severe weather. While walking outside during the ice storm was truly dangerous, neither disaster could, of course, compare to the impact of hurricane Sandy in New York, let alone the devastation of typhoon Hainan in the Philippines. Nevertheless, I could, at least, begin to imagine the shock that must accompany the first glimpse of a familiar landscape violently transformed by weather.

If a flood and an ice storm could render me speechless in twenty-first century Toronto, how did more extreme storms in the distant past affect the psychology of those who perceived in them the anger of a displeased god or malevolent spirit? Certainly despair and fear are clearly reflected in, for example, documents written in the immediate aftermath of North Sea gales during the Little Ice Age. Still, environmental historians of past climates have not yet fully interrogated the psychological impact of severe weather that grew more common in different climatic regimes. In part because it stretches the limits of our sources: largely absent from documents that refer to weather during the Little Ice Age are reflections on lingering feelings of displacement, disillusion and loss, but these emotions surely altered the lives of those who survived contemporary storms.

Climate historians often investigate relationships between past climate change, prevailing weather patterns, and agricultural production. However, the storms of last year also reminded me that networks that support transportation, the distribution of energy, and the flow of information are equally affected by severe weather. The consequences of such infrastructural disruption can be immense. In Toronto, thousands of people were left without power for more than a week, and some were poisoned by carbon monoxide as they struggled to heat their homes. Of course, infrastructural destruction is vastly greater in scale and consequence in the wake of hurricanes and typhoons. In the aftermath of Hainan, for example, the first priority of national and regional governments was to re-establish transportation networks so medicine, food and vital knowledge could be delivered to those in need.

Toronto Hydro map of those without power, December 23rd. Thousands are powerless in purple and blue districts.

Transportation systems during the Little Ice Age were far less effective than those we have today. For example, the Dutch Republic was renowned for its remarkably efficient and extensive waterborne transportation infrastructure. Still, for a modern traveller barges and boats moved at no more than a snail’s pace through the Republic’s network of canals. Travel on land through the bewildering web of unpaved roads and paths would be even more daunting. Not surprisingly, severe storms or especially cold winters could wreak havoc on mobility through the Dutch Republic.

On the other hand, the Dutch also demonstrated a remarkable capacity to adapt. When canals froze, they took to the ice in skates. When storm surges and river flooding inundated fields and towns, they used their boats. When some roads were closed by rain, others often connected the same destinations along slightly different routes. The landscape of the Dutch coastal provinces was largely artificial, reclaimed from the sea by a precarious network of dikes and sluices that required constant maintenance. Hence the Dutch, like most early moderns, were intimately connected to the ways in which they changed, and were changed by, their environments. When their environment provided the unexpected – a severe storm, for example – they were prepared to respond, even if those responses were not always effective.

In the winter of 1619/20, travel by boat was impossible. Instead, the Dutch used skates and horse-drawn or even sail-propelled sleds. Hendrick Avercamp, Winter Scene, 1620.

Perhaps it is unfair to compare the impact of storms in early modern Dutch cities to recent disasters like hurricane Katrina in New Orleans. Certainly the Dutch experienced their share of environmental catastrophe in their seventeenth-century Golden Age. Still, it is worth thinking about climate change in a broad context, with an eye to the past, present and future. Centuries of experience tell us that resilience to weather extremes is a matter of mental and material preparation. Systems must have many levels of redundancy, infrastructure must be flexible, worst-case scenarios must be anticipated before they happen. Whether expressed as exposed power lines or vulnerable levees, aged and precarious infrastructure is a recipe for disaster.

Hopefully 2014 is politically and environmentally tranquil in Toronto. Still, it helps to be prepared. For historians, that means knowing that we can - and should - contribute to conversations about the most important issues of our time.

~Dagomar Degroot

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In 2012 the Canadian government infamously announced changes to Library and Archives Canada (LAC) that made it much harder for researchers to access their country’s documentary heritage. The LAC’s mandate was transformed: rather than acquiring and maintaining a “comprehensive” collection, it now aimed merely to gather a “representative” assembly of Canadian documents. Funding was slashed, employees were laid off, new acquisitions were paused, documents were sold to private bidders, and resources were decentralized across Canada.

In the last month, interviews with scientists by The Tyee have revealed how the conservative regime’s attitude towards the environment meant that environmental archives suffered the most. Government scientists, who have asked to remain anonymous, report that the chaotic closure of world-class environmental libraries resulted in the destruction of priceless documents relevant to environmental and climate history. The same scientists allege that the government falsely assured that all documents were preserved through digitalization.

"The cuts were carried out in great haste apparently in order to meet some unknown agenda,” one scientist told The Tyee. “No records have been provided with regard to what material has been dumped or the value of this public property. No formal attempt was made to transfer material to libraries of existing academic institutions."

Painting of the HMS Challenger by William Frederick Mitchell, 1881.

The rich resources for environmental research at the St. Andrews Biological Station in New Brunswick are gone, as is the Freshwater Institute Library in Winnipeg, and the Northwest Atlantic Fisheries Centre in Newfoundland. At a time when historical climatology has increasingly turned to ship logbooks, the 50-volume logbook of the HMS Challenger has been destroyed. In 1876 the Challenger completed the first global marine research expedition, and its logbooks contain priceless data about the contemporary biosphere, hydrosphere and atmosphere. A copy of its logbooks exists outside of Canada, but it is less accessible for Canadian researchers.

The attack on environmental and, in particular, climate history by Canada’s Harper government demonstrates yet again that scientific or historical research into the environment is inherently political. Sadly, Canadian researchers cannot take even their archives for granted. We must do our best to digitalize what we can, ourselves, before it is lost forever.

Note: in coming years, digitalized sources relevant to climate history will appear on this website, where permission is granted.

~Dagomar Degroot

Links:

1. Save Library and Archives Canada.
2. Canadian libricide: Tories torch and dump centuries of priceless, irreplaceable environmental archives.
3. Fisheries and Oceans Library closings called loss to science.

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P. Mapfumo, University of Zimbabwe

This is an educational website. Most of its articles have described the insights and methodologies of scientists, humanists and ordinary people who study climates past, present and future. Many conclude with a simple warning: to effectively address anthropogenic global warming, we need more inclusive ways to transform learning into practice. However, very few of these articles have explored how that can be done. With good reason: interdisciplinary work is never easy, and even harder is research that incorporates diverse perspectives from those closest to the effects of climate change.

A new article in by Patti Kristjanson, Blane Harvey, Marissa van Epp, and Philip Thornton in the journal Nature Climate Change introduces “social learning” approaches as a way of integrating a wide range of perspectives into climate change research. According to the authors, social learning approaches "facilitate knowledge sharing, joint learning and knowledge co-creation between diverse stakeholders around a shared purpose, taking learning and behavioural change beyond the individual to networks and systems." In other words, social learning replaces traditional, linear educational relationships between those who have - or are perceived to have - money and power and those that don't. Many researchers have a vague desire to work with people "on the ground," but the concept of social learning provides a concrete, tested model for integrating diverse local perspectives into both research and subsequent practice.

The following table, taken from the article, provides an example of the social learning approach applied to agricultural practices in Kenya:

While improving agricultural practices was the key emphasis in Kenya, social learning also provides a means for more inclusive research. In doing so, it shortens the bridge between research and application. The first step of the social learning approach always involves gathering new information, and only in the second step are feasible options and solutions jointly identified with "research users:" those who actually apply information to practice. At every step along the way, local individuals - those actually affected by changing techniques and natural systems - are brought into the process. Ultimately all information is archived and made easily accessible for both researchers and local stakeholders.

In that light, it is ironic that those not affiliated with a research institution can access this article only after paying $18. Moreover, there are some limitations to the social learning approach. For example, it is still not easy to identify how diverse kinds of knowing could be incorporated into research into climates past, present and future. The social learning model provides a framework for community engagement, but local circumstances are so different that this framework must necessarily remain vague. The social learning model is also much harder to apply to studies of past climates that go back more than a few decades, especially when research results are not immediately translatable to practice.

Even then, however, community engagement often has value. Scholars should always seek to answer the big questions that matter to lay people. What are we doing, and why? How can those who aren't scientists or historians contribute? Will our results be accessible, and how are they applicable? The social learning approach cannot always be applied wholesale, but the social function and value of climate change research must be better articulated.

Patti Kristjanson, Blane Harvey, Marissa Van Epp & Philip K. Thornton. "Social learning and sustainable development." Nature Climate Change 4, 5–7 (2014): 5-7.

5f:T1b8a,

For nearly a century, interdisciplinary scholars have gradually reconstructed the existence of a so-called “Little Ice Age.” Their research is ongoing, but most now believe that average global temperatures declined by about one degree Celsius between the thirteenth and the twentieth centuries. The extent, meteorological consequences, and timetable of cooling varied from region to region, but sorting through these statistical complexities still yields an unmistakable downward trend in planetary temperatures.

Or does it? Economic historians Morgan Kelly and Cormac Ó Gráda of University College Dublin challenge the existence of a Little Ice Age (LIA) in a special issue of The Journal of Interdisciplinary History (JIH). Kelly and Ó Gráda examine recent reconstructions of European winter and summer temperatures from the medieval period to the twentieth century, but find “no statistical evidence of any major breaks, trends or cycles in European weather of the sort that one could associate with an LIA.” Kelly and Ó Gráda concede the existence of decades marked by extreme cold – the 1690s, for instance, or the 1810s – but to them these are mere blips in the statistical noise. They believe that climate historians have danced around this problem by changing the parameters of the LIA: some have identified its origins in the thirteenth centuries, and others in the sixteenth century, for example.

Kelly and Ó Gráda also challenge the “tenacious” idea that human history is driven by the direct influence of climate change. However, their argument is undermined by their use of long-term indices of wheat prices to supposedly correct the climatic reconstructions compiled by historical climatologists. Food prices are determined by more than the weather, even in preindustrial societies. A historian of past climates would more carefully tease out the complicated relationships between cultural structures, economic trends, environmental conditions and wheat prices, because the determinism dismissed by Kelly and Ó Gráda has all but vanished from serious scholarship on the LIA.

Hendrick Avercamp, Winter Scene on a Canal, ca. 1605.

The article published by Kelly and Ó Gráda fits neatly into a long pattern – a statistical trend! – of scholars in statistically rigorous disciplines challenging the conclusions of (historical) climatologists. In Merchants of Doubt, Naomi Oreskes and Erik Conway reveal how a cabal of right-wing physicists set out to undermine the science of global warming in the 1980s and 90s. Kelly and Ó Gráda certainly do not have such nefarious motivations, and they present some interesting correctives to popular narratives of the LIA. Still, their arguments against reconstructions of past climates are similarly problematic.

Fortunately, in its special issue on the Little Ice Age, the JIH provided space for rebuttals and further analysis. Perhaps the most compelling response was written by environmental historian Sam White, my co-founder at the Climate History Network. His article is well worth reading in its entirety, but its central point is simple: “Kelly and Ó Gráda have not detected a novel snag that somehow evaded hundreds of climate scientists.” Historical climatologists work with more than just records of grain prices. By employing a diverse mix of ice cores, tree ring records, historical sources and many other natural or documentary data that respond to weather, scholars have written thousands of articles that identify the LIA as the most significant climatic event for the 8,000 years prior to the onset of global warming. Of course, many of these articles were written outside of Europe, about regions other than Europe. White goes beyond the Eurocentric focus of Kelly and Ó Gráda to summarize the latest international, interdisciplinary research, which confirms that “the first four centuries of the last millennium (1000 to 1400) were warmer than the following four centuries (1400 to 1800).”

All the same, White concedes that Kelly and Ó Gráda are right to highlight the frequently inconsistent definitions of the Little Ice Age. To answer their objection, White presents three overlapping but compatible definitions of the Little Ice Age. According to the first, the world cooled between approximately 1400 and 1850, when the first influence of human greenhouse gas emissions ushered in the age of anthropogenic global warming. Under the second definition, the LIA was an “age of extremes” that lingered from the 1310s to the 1810s. Fluctuations – not general cooling trends – are paramount in this conception of the period. Finally, the third definition zeroes in on the coldest phase of the LIA, between 1580 and 1710, which coincided with a global socioeconomic “general crisis” in the seventeenth century.

Ultimately, White argues that serious scholars of the Little Ice Age have moved far beyond the straw man arguments that Kelly and Ó Gráda attempt to undermine. All the same, the kinds of objections presented by the economic historians are useful reminders that scholarship of past climates must be clear, consistent, and aware of the many influences that shape human history. The latest issue of The Journal of Interdisciplinary History reveals once again that otherwise problematic articles can be extremely useful for the conversations they inspire.

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Established in 1988 by the UN and the World Meteorological Organization, the Intergovernmental Panel on Climate Change (IPCC) is a scientific body that periodically summarizes the scholarly understanding of the world’s climate. In 2007, the panel’s fourth assessment report outlined in stark terms the likelihood of anthropogenic global warming. Since then, severe storms and drought have ravaged North America, Australia and Africa, yet unusually wet, cold conditions have accompanied some European winters. Through it all carbon emissions have continued to rise, now driven largely by developing nations. Today, the IPCC’s highly anticipated summary for policymakers was finally released, in lieu of its fifth assessment report that will be published later this year. In this article, I explore this landmark report and the responses it has inspired from the perspective of a climate historian.

Initially, the most striking aspect of the IPCC’s new summary for policymakers was not its content but the media reaction. The banner at CNN is currently: “A town that’s melting.” Its subheading: “climate change already happening in Alaska town.” Additional titles announce: “climate change: it’s us,” and “Miama’s rising water,” while an opinion calls for “common sense.” Not surprisingly, among major news networks the BBC has provided the most informative analysis of the IPCC’s report, and its banner, while not as large as CNN’s, nevertheless reads: “UN ‘95% sure’ humans cause warming.” Of course, the Fox News headline is in substantially smaller font, and its conclusion is characteristically fair and balanced: “Hockey Schtick: UN report ignores global warming pause.” Worse still is coverage given by the Times of India, which features only a link in diminutive font buried at the bottom of its website. Meanwhile the homepage for CCTV, a major Chinese broadcaster, contains no reference at all to the report. Taken together, headlines at the big media outlets confirm the enduring importance of partisan divisions in the global warming discussion. They also suggest that scholars, journalists, the IPCC, and indeed the UN must do more to raise awareness of global warming in countries that will be most affected by its consequences. Still, the banner headlines on many centrist news outlets in the West are encouraging.

For those who have paid heed to the relentless debate about global warming, much of the action in the IPCC's fifth summary for policymakers happens in the first few pages. In previous days and weeks, so-called climate “skeptics” flooded the airwaves, encouraging rampant speculation about whether the alleged “pause” in global warming would feature prominently in the IPCC's new report. In fact, in its second page the IPCC's summary actually confirms that:

The IPCC affirmed that average global temperatures at sea and on land have risen by 0.85 degrees Celsius since 1880, although that will come as no surprise. What does impress, however, is the IPCC's explicit repudiation of the false narrative of the "pause." Climate historians know better than most that climatic reconstructions can be manipulated with ease. Start your graph of annual temperatures with a year of anomalous warmth, and you're bound to discover long-term cooling. Begin with an unusually cold year, and you'll find just the opposite. That is precisely why scholars must set their temporal and geographic parameters before reconstructing past climates. What region are we examining? For what time, and why? With what sources? What are the limitations of those sources? These questions are essential for the accurate reconstruction of past climates, and the answer can never be: "because of the expected result." Moreover, to unravel why variations in temperature occur, we must also seek the stimulus - the "forcing" - for cooling or warming. Is a volcanic eruption responsible for a few unusually cold years? Is an intense El Niño to blame for a really hot year? Neither event need contribute to a long-term climatic trend.

Not surprisingly, skeptics eager to discredit the scientific consensus around global warming have ignored these questions. Instead, they have arbitrarily started their climatic reconstructions at 1998, a year of extreme warmth, in order to highlight supposed cooling since then. Unfortunately for them, the scholars of the IPCC have included this paragraph:

In other words, the presence of short-term fluctuations in climate does not throw into doubt the existence of long-term climatic trends. If anything, the impact of strong El Niño in 1998 reveals what can happen when an entirely natural event that stimulates warming compounds the the influence of anthropogenic greenhouse gases. Still, the IPCC's fifth summary did include these passages:

Those paragraphs will probably be manipulated by skeptics and misinterpreted by many journalists. While they seem to suggest that there has been a pause in the warming trend, the context matters. The surrounding passages confirm that model accuracy has improved, further strengthening projections of future warming. However, in 10 or 15-year intervals, natural signals can mask the anthropogenic warming trend. In other words, volcanic eruptions can stimulate short-term cooling, but, again, that hardly rules out long-term warming. In short intervals some natural influences will surprise scientists and confound models, because we are still learning more about the intricacies of our world's climate. Nevertheless, the big conclusions are still the same: the earth is warming, we're to blame.

The IPCC's summary for policymakers also addresses climates in the more distant past. Another argument frequently advanced by skeptics holds that the Medieval Climate Anomaly - previously known as the Medieval Warm Period - was actually accompanied by hotter temperatures than we face today. Their conclusion is that modern warming isn't a big deal, and falls within natural variability. Of course, the cause of current warming is more important to climate scientists than the scale of warming to date, because it is precisely that cause which will trigger future warming far beyond anything humanity has encountered. Nevertheless, the IPCC's report also discredits the idea that medieval warmth exceeded or matched modern temperatures:

In subsequent pages, the IPCC's report describes the worrying findings presented in thousands of scientific papers during the past six years. Oceans are warming, polar ice caps are shrinking and sea levels are rising, while the atmospheric concentration of carbon dioxide, methane, and nitrous oxide have risen to levels unseen in over 800,000 years. In its most important conclusion, the panel's report reveals that greenhouse gases emitted by human activity are now 95% certain to have caused recent warming. These emissions have affected carbon cycle processes, stimulating further warming from natural sources (for example, methane hidden under melting permafrost). Meanwhile, the ocean has absorbed 30% of anthropogenic carbon dioxide, causing dangerous ocean acidification.

The IPCC's fifth summary concludes that warming in the coming century will likely fall between 1.5-4 degrees Celsius. Moreover, it is more likely that warming will exceed a catastrophic 6 degrees Celsius than fall beneath 1 degrees Celsius. The lower range of this estimate is 0.5 degrees Celsius lower than it was in the IPCC's fourth assessment in 2007, owing in part to the slight divergence between model projections and climatic trends in the past decade. It is possible that the range will be adjusted upward in the IPCC's next report, as model simulations and average global warming converge again. Either way, our best guess for the future hasn't changed much: we probably face warming of approximately 3 degrees Celsius worldwide by the end of the century.

Social and environmental vulnerability to climate change, from low (pale green) to high (purple).

Of course, a 3 degree Celsius rise in average global temperatures does not mean each day will be three degrees warmer, no matter where we are. In many regions, warming will be expressed in extremes: a doubling, or tripling, of days accompanied by severe heat, along with far more dangerous storms and flooding. Moreover, warming in some countries will far outstrip the global average, and demographic, social or environmental conditions already increase the vulnerability of many of these countries to climate change. In 2011, scholars at Maplecroft, a global risk analytics company, created the above map of global climate change vulnerability by analyzing 42 social, economic and environmental variables. News outlets in China and India take note: it is precisely the countries that increasingly contribute most to warming that have the most to lose. In that context, let us hope that the dire projections in the IPCC's fifth summary help moderates bridge the partisan divide to inspire concrete responses to climate change in the developed west.

~Dagomar Degroot

Further reading:

Climate scientist Michael Mann, author of The Hockey Stick and the Climate Wars, measures claims by climate skeptics in light of the IPCC's fifth summary for policymakers.

On September 28th, the scientists of the International Geosphere-Biosphere Programme respond to the IPCC's fifth summary.

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Contributing Author: Benoit S. Lecavalier

August 18th, 2013 marked the start of a two week long workshop called the Advanced Climate Dynamics Course (ACDC). The venue was located in a former fishing village in the Vesterålen islands of Arctic Norway, a little place called Nyksund with a population of slightly over a dozen permanent residents. We were there for more than just hiking through the great outdoors, eating the local food, and performing local outreach. We were there to discuss what many call small talk: the climate. Organized by European and North American Universities, this event attracted internationally renowned researchers and graduate students, gathered there to discuss the climate dynamics of the last deglaciation. Twenty thousand years ago, during the last glacial maximum, the climate was cooler, the Greenland and Antarctic ice sheet were larger, and gargantuan bodies of ice rested across North America, the British Isles, and Scandinavia. Consequently, the sea-level was lower than it is today by over 120 meters. The emphasis of the workshop was to discuss how the climate system transitioned from glacial to present interglacial conditions.

The seminars began by summarizing our present understanding of climate on time-scales of thousands of years. The driver, often referred to as the pacemaker for the ice ages, is the changes in the Earth’s orbit around the sun. These gradual changes in the Earth’s orbit affect incoming solar radiation at the Earth’s surface, which can either facilitate the growth of an ice sheet or deter it. However, countless feedbacks within the climate system render the situation complex. For example, ice sheet’s reflective nature deflects radiation back into space affecting the available energy at the surface. In addition ice sheets, which can rival mountain ranges in size, affect atmospheric jet streams and deflect storm tracks as well as precipitation patterns. To understand these feedbacks within the climate system we have to look at paleoclimate records: terrestrial and marine records of past climate.

The following days were spent going over climate proxies, which preserve physical characteristics of past climatic conditions. These tell us about past temperatures on land and in the ocean, how vigorously the oceans circulated, and past sea-levels, among many other things. After being presented with collections of paleoclimate records, we could speculate on the role of the atmosphere and ocean during the deglaciation. The question that came came to mind: if the ice ages are driven by slow gradual changes in the Earth’s orbit around the sun, what processes, feedbacks, and mechanisms could punctuate the system with such abrupt and rapid climate change?

Evening in Nyksund.

We reviewed the literature to investigate the consensus on what is currently understood and what observations lack a proper explanation. Our review emphasized the necessary role of geophysical modeling of the climate system to understand how all these complex processes are intertwined. State-of-the-art atmosphere-ocean general circulation models tell us about the state of the atmosphere and ocean, while glacial system models reveal the response of ice sheet to past climate change and the resulting change in sea-level. Atmosphere-Ocean models are predominantly applied for the past and future 100 years, so the question remains: what were the climatic conditions over the ice sheets thousands of years ago? What climate forcing led to ice sheet instabilities, causing the flow of iceberg armadas in the North Atlantic? To which extent did the fresh water from these icebergs affect the circulation of the Ocean? How have these changes in circulation affected global heat transport and the carbon cycle? What about global temperatures? Fortunately, we are beginning to answer these questions thanks to international cross-disciplinary collaborations, which are often initiated by workshops such as the ACDC.

Many atmosphere-ocean modelers take an interest in simulating the deglacial climate, with help from the glaciological community who provide past ice sheet reconstructions. These scientists have discovered that massive ice sheets show the potential to deflect atmospheric stationary waves. The ice sheets respond to climatic shifts, and in warmer conditions they can change dynamically by releasing icebergs into the ocean. Fresh water melting from those icebergs produces density differences in the Atlantic Ocean which slows down the formation of heavy deep water, affecting global circulation. This change in ocean heat transport cools the North Atlantic, while the Southern Oceans warm in a compensating fashion. The models simulate these dramatic climate events, hinting at underlying mechanisms and illuminating the observations found in paleoclimate records. This goes a long way towards explaining how the Earth as a whole warmed out of the glaciation and why records in the North Atlantic reflect quick warming with subsequent rapid and prolonged cool period before finally stabilizing to present conditions.

However, the story is far from understood, for every answer brings new questions. The workshop got everyone thinking about possible avenues of research which will have to be investigated to address our questions. That is why we gathered there in that little Norwegian village. It was to exchange ideas, data and model predictions, to work together and form collaborations, and to piece together a story that shaped humanity and still affects us today.

Researchers at the Advanced Climate Dynamics Course, 2013.

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A week ago I returned from what was, surprisingly, my first trip to Germany. This year the European Society for Environmental History convened its biannual conference in Munich, a city I’ll remember for its beautiful architecture, sensible public transit and delicious beer. No fewer than fifteen climate history panels were part of the conference, and despite my best attempts I couldn't attend them all. Still, I decided to share some of what I learned (or remembered) while listening to papers that were good enough to keep me from exploring Munich. Note that for the purposes of this little article, the terms “climate history” and “historical climatology” are synonymous.

1. Climate history must be inclusive to be effective.

There is only limited value in mining one kind of documentary source for evidence of past weather and, in turn, past climate change. Of course, the value of such work fluctuates with the source under investigation: registers of past events called chronicles are notoriously prone to exaggeration, for example, while ship logbooks provide standardized, easily quantifiable and remarkably reliable weather observations. Still, a reconstruction of past climate that makes any claim to accuracy must, where possible, employ a wide variety of documentary evidence compiled by many authors. These reconstructions are strengthened when meteorological information contained in some documentary sources can be verified using the data contained in other documents. They gain even more credibility alongside scientific evidence like model simulations, or statistics developed using natural archives (ice cores or tree rings, for example). Good climatic reconstructions are necessarily interdisciplinary, and we should think carefully about what we are really saying when we discuss observations written by a single author, in a single source. Are we reconstructing the climate of a vast region across the decades, or are we engaging in literary criticism?

If interdisciplinary work is essential to historical climatology, interactions between sub-disciplines are just as important. Climate history is often considered a sub-discipline of environmental history, which, in turn, is one genre in the broader field of history. Agricultural history, forest history and energy history are all among the sub-disciplines that together constitute environmental history. Like climate history, they lose significance when divorced from one another. Reconstructions of past climates are fascinating, but historians can also incorporate the many different sub-disciplines and genres of their profession to do something scientists can’t: weave the history of climate into the history of humanity. The narratives we get can be as valuable as the models developed by scientists as we struggle to understand our plight on a warming planet.

Beautiful Munich: the perfect city for a conference.

2. We're only scratching the surface of relevant documentary evidence.

Chronicles and weather diaries have long formed the backbone of the documentary evidence used to reconstruct past climates. Questions of interpretation hound both sources, however, and these days, correspondence and ship logbooks are increasingly in vogue. In Munich I heard scholars like Rudolf Brázdil describe how correspondence related to the collection of taxes can yield strikingly detailed climatic reconstructions. Tax records can be placed alongside court documents, toll accounts and maintenance registers as largely quantitative sources that can yield rich climatic data if interpreted using qualitative evidence. New sources – and new methods of source interpretation - can provide data about wind patterns, hailstorms, and other previously unexamined meteorological conditions, deepening our understanding of climate change.

3. We need new ways of conceptualizing the relationship between climate change and human history.

Fernand Braudel, perhaps the greatest historian of the twentieth century, introduced a revolutionary way of conceptualizing time. According to his notion of “total history,” different kinds of historical change transpire differently across time and space. Environmental or economic transformation at a vast scale spanned the centuries, yet the historical “event” was immediate. Understanding the past from this perspective allowed him to gather the entire Mediterranean world into a single narrative using the huge, lumbering structures of history.

Braudel's conception of historical change. Source: http://goo.gl/MSqC4U

The problem for historical climatologists – and indeed, all environmental historians – is that Braudel was wrong. Interdisciplinary research has revealed that many historical structures can be brittle; they can break quickly with immediate yet regionally specific ramifications. For example, climate change influenced by volcanic eruptions and the subsequent expansion of polar ice could alter prevailing weather patterns over the North Sea in one cruel winter. However, the same processes behind routinely cold winters in northern Europe could bring not frost but rather drought to the Mediterranean.

So different kinds of historical change can occur across many scales of time and space, and that complicates our attempt to conceptualize connections between past environments and historical events. Human history cannot be modeled – we simply lack all of the necessary variables – but in recent years environmental historians have made great progress going beyond the problematic concepts like footprint metaphor or social metabolism in their efforts to conceptualize the connections between nature and society. In this effort historical climatologists lag behind their peers, and for that reason climate histories can devolve into lists in which weather events likely stimulated by a climatic shift cause environmental changes that contribute to one event after another in the history of a particular region. Historians need to work with colleagues across many disciplines to develop ways of understanding relationships between climate, weather and human history. These ways of understanding might not completely explain the past, but they might help us conceive of historical change more clearly, with insights applicable for our future on a warming planet.

~Dagomar Degroot

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For those interested in climates past and present, trees do more than absorb carbon dioxide. Seasonal changes in cellular growth near the bark of a tree leave rings buried in its wood. The size of those records is tied to the growth of the tree; a good year will imprint a thick ring, while hard times leave mere slivers. Anyone who's ever owned a plant will understand that most trees need abundant sun, moderate temperatures and sufficient water. Of course, gardeners are aware that different plants - from weeds to trees - respond to different conditions. By researching the peculiar tastes of various tree species climatologists can use tree trunks to reconstruct yearly fluctuations in temperature and precipitation, sometimes over hundreds of years.

The resulting reconstructions have been featured on this site ("Does tree ring data reflect global cooling? July 9, 2012"). With good reason: tree rings enable reliable climatic reconstruction for most parts of the world, especially in temperate regions where the contrast between seasons usually yields more discernible rings. However, most sources useful for the reconstruction of past climates have their shortcomings, and these inevitably stimulate controversy.

Tree rings are no exception. Sulphur released into the atmosphere by volcanic eruptions of sufficient size at the right locations can cool the world's average temperature. Strangely that global cooling, while recorded by other sources and climate models, is not represented to the same extent in tree ring data. A new study by Michael Mann, Jose Fuentes and Scott Rutherford in the journal Nature Geoscience has suggested that trees in some altitudes simply stop growing when temperatures plummet below a certain threshold. Many trees would survive, and for those trees the next tree ring would therefore record growth only after temperatures had rebounded above that threshold. It is possible, therefore, that climatic reconstructions compiled using tree rings are less accurate than previously thought.

No fewer than twenty-three scientists responded to these claims, and the subsequent debate is nicely summarized by Scott Johnson at Ars Technica. Whatever its resolution, the controversy highlights the weaknesses of climatic reconstructions that use just one kind of source. The most reliable reconstructions of past climates and, for that matter, human history are generally those that incorporate a wide-ranging and diverse selection of evidence. For some weather conditions, in some places, for some time, evidence useful for climatic reconstruction can include all manner of sources, involving not only tree rings, plankton deposits, ice cores and other records accessible by scientists, but also surviving documentary records from literate cultures.

Logbook kept aboard the vessel "Wapen van Hoorn," sailing from Holland to Asia in 1627.

The cross-disciplinary dialogue encouraged by this diversity of sources can break down, however, when scholars broaden their focus. Changes in weather conditions like wind direction that may be associated with climatic fluctuation aren't easily reflected in scientific data. Reconstructions therefore rely heavily on, for example, logbooks kept aboard ships that record daily weather. On the other hand, past cultures that communicated information orally have left us few sources useful for climatic reconstruction, and when piecing together the climatic shifts that affected such civilizations we must depend on, for example, tree ring data. As our interest enters the distant past we leave behind both documentary sources and tree ring data, and our reconstructions must increasingly rely on ice cores. Beyond 1.5 million years into the past we must turn to sediments and consider increasingly indirect consequences of climatic fluctuation, as our reconstructions diminish in accuracy.

Ultimately we cannot measure or understand global warming without reference to the past; after all, the world must be warming relative to what came before. Moreover, our best guess of what may happen in the future can come through an analysis of warmer (and colder) periods in our past. For that reason it is critical that we grasp the limitations of the sources that we use to reconstruct the climates of that past. Ultimately the best answers are always found through diversity: diversity of sources, methodologies, and perspectives.

Note: I will be discussing some of these themes next week at the PAGES Open Science Meeting in Goa, India.
~Dagomar Degroot

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As this is published, so-called "Frankenstorm" hurricane Sandy is merging with a winter gale and bearing down on the American east coast. The deaths of sixty people in the Caribbean will likely represent this historic storm's most direct and poignant toll. However, as panic spreads through the most densely populated region of the United States it is the hurricane's potential to influence the American election and, possibly, the shape of the world in years to come that has most captured the world's attention. Whether the worst fears of meteorologists come to pass or not, Sandy presents a unique "teachable moment" for historical climatologists, many of whom study the interactions between past weather and historical events.

The most fundamental lesson we can glean from the impending catastrophe is simply that weather affects history. Most historical narratives still focus on events within purely human spheres, describing changes in relationships between classes, for example, or cultural trends. The rise of post-modernism in particular has left some historians suspicious of attempts to describe environmental influences and, ultimately, "what really happened." Of course, there are the limits - both practical and conceptual - that cloud our ability to reconstruct the past and make sense of relationships between human histories and, for example, severe weather events. Nevertheless, hurricane Sandy reveals that many histories are little more than interesting stories unless they at least attempt to address environmental influences.

New York: possibly facing the worst storm in its history. Reuters.

A second lesson that will become increasingly evident in coming days, weeks and years is similarly simple: some of hurricane Sandy's most important influences will be counter-intuitive. We may find, for example, that widespread fear drove many people to vote early, paradoxically increasing voter turnout. As I charted how weather patterns influenced by past climatic shifts affected Dutch East India Company ship journeys, for example, I expected to find that more frequent storms in colder climates proved devastating to the Company and its sailors. Instead, because East Indiamen were gigantic, solidly-built ships, many storms actually benefited crews by pushing their ships forward more quickly with their high winds. Because so many sailors died of disease while at sea, shortened journeys, influenced by storms, probably saved lives. Environmental influences are rarely straightforward, and historical climatologists know this better than most.

In the aftermath of hurricane Sandy's landfall, it's likely that many will describe how the storm "caused" devastation along the East Coast and, in turn, altered the election. The third and final lesson, then, is that weather events are but one influence among many. Natural disasters occur at the intersection of human and environmental histories; indeed, while "natural" usually refers to stimuli that, at least until recently, have largely existed beyond human influence, there is no "disaster" without human settlement. Teasing out how exactly hurricane Sandy affected the East Coast, how it helped change the election, and what social structures were especially vulnerable will be a painstaking task. Luckily, there is an entire field of study devoted to unraveling those relationships.

~Dagomar Degroot

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As a historical climatologist, I work in an avenue of environmental history that bridges historical and scientific methodology to reconstruct past weather, investigate societal vulnerability to climatic fluctuation, and uncover cultural representations or responses to climate. Originally published at Activehistory.ca, this is the second in a series of articles that explain how my training as a historian helps me engage in the ongoing discourse about global warming. In this post I’ll explore problems in the understanding of the relationship between society and climate in models of the future and descriptions of the past, before considering how historical climatologists can help forge more accurate visions of humanity on a warmer planet.

In a recent article for Osiris Mike Hulme argues that conceptions of the relationship between climate and society have been troubled by two opposing fallacies. The first - “climate determinism” - imbues climate with decisive influence in individual and collective behaviour, while the second – “climate indeterminism” – strips climate of all influence in human affairs. Climate determinism has a long history, with roots in the eighteenth-century belief that differences in the world’s climate were responsible for the geographical distribution of contemporary human achievement. Hulme argues that modern scholars perpetuate a new form of determinism, which he calls “climate reductionism,” by using models to predict that global warming will cause mass species extinction, waves of climate refugees, economic collapse and, ultimately, the end of our species. For Hulme, the future political, social, economic and environmental relationships that shape a warming climate’s influence on humanity are unknowable, and no model can chart a calamitous future with so many uncertain variables.

Climatic determinism and indeterminism stem not just from our desire to peer into the future, nor our attempts to explain the present, but also from our examination of the past. Hulme suggests that, in academia, geographers have tended to write climatically reductionist histories, while climatic indeterminism has often been the purview of historians. There is some truth to this, but the reality is a bit more complex. The study of past climatic fluctuation naturally involves more disciplines than history and geography, and the rise of environmental history has gradually altered how most historians perceive nonhuman variables. Meanwhile both determinism and indeterminism frequently coexist in the same narratives.

Take, for example, anthropologist Brian Fagan’s The Little Ice Age, a popular and beautifully written exploration of medieval and early modern climatic shifts. Fagan opens with a pair of graphs. The first records the fluctuating history of global temperatures over the last millennium, providing a list of “Climatic and Natural Events,” while the second charts the ebb and flow of human history over the same period. The implication is, as Fagan writes, that, “humanity has been at the mercy of climate change for its entire existence.” However, Fagan also insists that, “you certainly cannot argue that climate drove history in a direct and causative way.” How then can we make sense of Fagan’s claim that, “like the Norse conquests, [gothic] cathedrals too are a consequence of a global climatic phenomenon, an enduring legacy of the Medieval Warm Period”?

Works of historical climatology that hold determinism and indeterminism in appropriate tension can inform the quest for nuanced and, hopefully, realistic visions of humanity’s future on a warmer planet. The reliance of historical climatology on fragmentary historical documents – in which weather is often an afterthought - to supplement or expand climatic reconstructions developed in other disciplines would seem to stimulate a self-critical understanding of the complexity of the questions we seek to answer. Unfortunately, many studies in historical climatology still lack explanatory models, consider only extremes in agrarian economies, and develop narratives of inevitable decline in the face of climatic fluctuation. This is in spite of the trailblazing work of Christian Pfister and others in the 1980s to formulate models explaining the actual processes by which climate and human history interact. Conceptual models, theories and, above all, an awareness of epistemological assumptions and methodologies can help us realize, for example, that a decade of storminess does not cause a shipwreck. A shifting climate is locally felt through altered regional environments, which can, in turn, kindle culturally mediated weather phenomena that limit or expand the possibilities open to a ship’s crew. Such insights can help stimulate projections of the future that embrace, for example, forms of local knowledge, cultural differences affecting societal vulnerability, and an awareness of the nonlinear course of socio-economic development.

With that in mind, it is important to note that works of environmental history and historical climatology that speak to the broadest audience are often those that embrace some level of determinism. Jared Diamond’s Collapse or Guns, Germs and Steel might lack balance, but they popularize narratives that are critical in a time of capitalist overexploitation of the world’s resources. Similarly, the projections that Hulme dismisses might lack sophistication, but the sense of alarm they stimulate and convey is necessary in the face of a climatic catastrophe. Balancing the nuance of our narratives with their ability to reach a wider audience will be one of the major challenges faced by scholars of climates past and future in the decades to come.

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It’s always been my belief that historians either consciously or unconsciously situate their histories in the context of the present. History is inevitably “active,” no matter our occasional insistence on pursuing history for history’s sake. This is no surprise to environmental historians who, more than colleagues operating in any other historical genre, explicitly address contemporary issues in their often declensionist narratives. As part of a small but growing number of environmental historians exploring the relationship between climatic changes and human affairs, I am drawn into modern debates about global warming whether I like it or not. That’s why I decided to use my first few blog posts to reflect on how my research as a historical climatologist has allowed me to address some big ideas in the discourse about global warming today.

A couple years ago I spoke to a former Liberal member of parliament who had played a key role in developing Canada’s climate policy in the 1990s. He related to me that one of the key difficulties of his job was tackling the enormous complexity of the projected climate shift, where warming in one region might coincide with cooling somewhere else. “After all,” he said matter-of-factly, “it’s not global warming; it’s climate change.” Since then I’ve heard this distinction elsewhere, particularly in reference to periods of unusually cold weather, like the last two winters in Europe. Far from mere semantics, to me the use of the term “climate change” rather than the more alarming “global warming” seems like a new wrinkle in the attempt to discredit or diminish the reality of a warming climate. It also fundamentally misunderstands the nature of a climatic shift.

I study the social effects of the Little Ice Age, a period of climatic variability and general cooling that lingered from the fourteenth to the nineteenth centuries. As a result I know there’s some truth to the idea that a climatic shift means different things for different regions. Owing to a specific intersection of environmental and social structures there are places that are more or less vulnerable to the weather patterns typical of a prevailing climatic regime. Moreover during the coldest decades of the Little Ice Age some regions experienced more precipitation and some less; some areas were wracked with storms, while others grew more tranquil. Indeed, some years, even decades were warmer than average, not just for isolated regions but for the world as a whole. Finally, different parts of the world can have different climatic chronologies: China and Japan appear to have been warm when Europe was cold after the fall of Rome, then cooled as Europe experienced unusual warmth in the high medieval period.

All this complexity can, in the right hands, deliberately obscure a very simple reality: climate deals with nothing more than generalized weather. For all its complexity the Little Ice Age cooled the world’s climate for several hundred years, just as the world’s climate is rapidly warming now and will continue to warm for at least the century to come. After all, the winters that chilled Europe in 2010 occurred during one of the warmest years in record. It is important for policymakers to avoid the assumption that every region will experience a climatic shift in similar fashion, but it is even more important that we don’t lose sight of the forest for the trees.

~Dagomar Degroot

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Bibliography

More photographs from the Arctic:

The team:

1. Climate history must be inclusive to be effective.

2. We're only scratching the surface of relevant documentary evidence.

3. We need new ways of conceptualizing the relationship between climate change and human history.

Study: aerosol pollution delayed warming in Eastern US. April 26, 2012.

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