Dr. Dagomar Degroot, Georgetown University
International climate change agreements have long aimed at limiting anthropogenic global warming to 2°C Celsius, relative to “pre-industrial” averages. Yet in early 2015, more than 70 scientists contributed to a report that warned about then-poorly understood dangers of warming short of 2° C. Several months later, Parties to the United Nations Framework Convention on Climate Change (UNFCCC) met in Paris and reached what seemed to be a promising agreement that aimed at keeping global warming to “well below” 2° C.
The Paris Agreement invited the Intergovernmental Panel on Climate Change (IPCC) to prepare a special Assessment Report on the consequences of, and means of avoiding, warming on the order of 1.5° C. The IPCC accepted the invitation in 2016. This week, it published its report, together with a short summary for policymakers. In it, 91 scholars from 40 countries summarize the results of more than 6,000 peer-reviewed articles on climate change.
The published report still captured headlines and provoked justified alarm. Here’s what struck me as I read through it this week.
The Importance of 0.5° C
The new assessment report is really all about half a degree Celsius. Since the world has now warmed by roughly one degree Celsius since a 1850-1900 baseline, only half a degree Celsius separates us from 1.5° C of warming, which in turn is of course only half a degree removed from the infamous 2° C threshold previously emphasized by the IPCC and the UNFCCC.
So, what difference does 0.5° C make?
It depends on the perspective you take. The new report shocked many by predicting that some of the profound environmental transformations long anticipated with 2° C warming, relative to the nineteenth-century baseline, would be well underway with just 1.5° C warming. By 2100, for example, sea levels could rise by up to 0.77 meters if temperatures increase by no more than 1.5° C, which may only be around 0.1 meters lower than the level they would reach with 2° C warming.
Worse, it now seems that marine ice cliff instability in Antarctica and the irreversible collapse of the Greenland ice sheet – two frightening scenarios that could each raise global sea levels by many more meters and set off additional tipping points in the climate system (see below) – could be triggered by just 1.5° C warming. Perhaps 90% of the world’s coral reefs could be lost with 1.5°C warming, compared to every reef in a 2° C world. In one sense, there seems to be a huge gulf between where we are now and where we’d be with another half-degree of warming, and comparatively little difference between a 1.5° C and a 2° C world.
Yet in other, critically important ways, there could be an equally big gap between the 1.5° C and 2° C scenarios. Of 105,000 species considered in the report, three times as many insects, and twice as many plants and animals, would endure profound climatically-determined changes in geographic range in a 2° C world, relative to a 1.5° C world. A threefold increase in the terrestrial land area projected to change from one ecosystem to another also seperates the 1.5° C and 2° C worlds.
The importance of just half a degree Celsius is particularly clear at local and regional scales. Warming is greater on land than at sea, and much greater across the Arctic. In cities, urban heat islands double or even treble global warming trends. In many regions, extreme weather events – droughts, torrential rains, heat waves and even cold snaps – are now much more likely to occur than they once were. Superficially modest trends on a global scale can mask tremendous shifts in local or regional weather.
The critical importance of warming on the order of just half a degree Celsius for ecosystems around the world invites us to revisit some of the more controversial claims made by climate historians about the environmental impacts of past climate change. There is, of course, a range of natural climatic variability that most ecosystems can accommodate, and we are on the verge of leaving that range across much of the Earth, if we have not left it already. Yet it now seems painfully clear that even small fluctuations in Earth’s average annual temperature can have truly profound ramifications for the regional or local ranges and life cycles of plants, animals, and microbes.
Risk, Uncertainty, and Scale
Back to the difference between 1°, 1.5°, and 2° C warming. Perhaps the most alarming part of the new assessment report – one seemingly lost on many environmental journalists – is what it says about the value of the whole project of establishing numbers that become touchstones in climate change discourse.
Beginning well before 2015, climate scholars pointed out that attempts to emphasize the danger of 2° C warming risked creating the false impression, among policymakers and the public, that the worst impacts of climate change would suddenly unfold only after Earth passed that threshold. I’d wager that for most people, the 2° C limit still seems like a distant threat, one we will eventually face only if we don’t gradually reduce greenhouse gas emissions. Yet the new report confirms that the 2° C threshold was all along an arbitrary standard, one that did not really convey the nature of the threat we face.
It is now plain that we will not only trigger vast and irreversible changes to Earth’s climate system with 1.5° C warming, but worse: we have already engaged some of them, and we may unlock more in coming years. Nature, unfortunately, cares little for our nicely rounded numbers.
There’s more. Even before its release, some climate scientists and activists criticized the new report for understating the extent of present-day warming, and more importantly: ignoring the so-called “fat tail” threat of runaway warming triggered by positive feedbacks, or “tipping points,” buried within the climate system. Of these feedbacks, the best known is probably the ice-albedo feedback, where modest warming melts bright sea ice that normally bounces sunlight back into space, replacing it with dark water that absorbs solar radiation, contributes to more warming, more melting, and so on. Another well-known feedback involves methane that now lies buried in Arctic permafrost and frozen seabed sediment. Warming is already melting tons of methane into the atmosphere, where it traps far more heat than carbon dioxide. Again: warming will lead to more melting, more warming, and so on.
These feedbacks have historically converted relatively minor sources of warming or cooling into profound climatic trends. Yet scientists don’t know precisely how all such feedbacks work, or when exactly they are triggered. If we’re lucky, we won’t trigger most of them at all, not even if we reach that 2° C threshold. Yet it’s also possible that we have already set some of them in motion, in ways that will irreversibly lead us to runaway warming. In that case, our children – or our children’s children – will have to survive a “hothouse” world, one fundamentally different from our own.
This brings us back to the issue of risk and probability, which the IPCC’s scientists stress in every assessment reports. The IPCC expresses uncertainty using the terms “confidence” and “likelihood,” and it is very important to decode these terms in order to understand the new assessment report.
In it, the terms “very low,” “low,” “medium,” “high,” and “very high” confidence all refer to the confidence the report authors have in key findings. Their level of confidence reflects both the quality, quantity, and type of evidence used to support those findings, and the extent to which different lines of evidence agree with the findings. In the report, the terms “exceptionally unlikely,” “extremely unlikely,” “very unlikely,” “unlikely,” “about as likely as not,” “likely, “very likely,’ and “extremely likely” all refer to the statistical probability of outcomes actually happening, based in part on the findings.
Unfortunately, these definitions are buried on page 40 of the first chapter of the new assessment report. Yet they make it impossible to conclude, as so many journalists have written, that the new report predicts what will happen in the future. Using such language plays into the hands of climate change deniers, who rightly point out that nobody can predict the future with certainty. Climate scientists, of course, know that better than most, which is why they always attempt to qualify and quantify their predictions.
Climate historians also deal with probability. As I point out in a forthcoming article, we can never really reconstruct the local or regional manifestations of climate change with perfect certainty, nor can we be completely sure of local connections between climatic trends and human or animal behavior. Some of the most interesting relationships we can discern are among the least documented, especially once we get away from the usual European or Chinese focus of most climate historians. At its best, climate history therefore deals explicitly with risk and uncertainty by qualifying its major findings.
Other historians tend to rebel against such qualifiers. More than one peer reviewer, for example, has told me to be more authoritative, to forcefully express that climate change directly caused humans to do something in the past. To these historians, qualifiers communicate the kind of weak uncertainty that seems to suggest that an argument is not well grounded on solid scholarship.
These criticisms come from the practice of traditional historical scholarship, where documents seem to communicate exactly what happened to whom, and when. Yet when we work with different kinds of sources, from natural archives, those relationships cannot always be clearly or simply established. The more, and more diverse, information you have, the more uncertain the past can become. Still, abundant information from many natural and human sources can also provoke questions, and suggest relationships, that traditional historians have not imagined. The best documented and seemingly most certain version of the past, in other words, isn't always the most accurate.
A Determined Future (and Past?)
The new IPCC report also abounds with exactly the kind of sweeping statements that historians – myself included – have attacked in the past. In a brilliant 2011 article I often ask my students to read, Mike Hulme criticizes how the predictive natural sciences have promoted a new variant of the climate determinism many Europeans once used to explain the expansion of western empires. Because climate change can be predicted more easily than social change, Hulme argues, climate science has promoted a kind of climate reductionism that “downgrades human agency and constrains the human imagination.” Surely, the human future will not be crudely determined by climatic trends.
And yet, the IPCC concludes that climate change will probably exacerbate poverty, provoke catastrophic migration, impede or annihilate economic growth, amplify the risk of disease, and, in short, sharply undermine human wellbeing, especially for “disadvantaged and vulnerable populations, some indigenous peoples, and local communities dependent on agricultural or coastal livelihoods.” While there will be ways for communities and societies to adapt, the IPCC’s summary for policymakers finds that “there are limits to adaptation and adaptive capacity for some human and natural systems” in even a 1.5° C world. Warming, in short, will likely provoke human suffering.
Should we be skeptical of such claims? As usual: it’s complicated. While historians like to emphasize complexity and contingency in narratives of the past, scientists search for patterns in complex systems that permit predictive models. Many historians therefore feel uncomfortable when asked to anticipate the future in light of the past, and that discomfort is partly to blame for the unfortunate absence of historical scholarship in the new assessment report. Of course, scientists have no such problem. Their models can indeed be deterministic – by necessity, they only consider so many variables – yet they still provide some of our best perspectives on what the future might have in store.
With that said, it's important to again stress that many of these models should be taken as estimates of what might happen in our future. They cannot tell us what will actually unfold. History does teach us that the human story involves both steady trends and sudden leaps: technological breakthroughs, revolutions, and the like. It is simply wrong to conclude that even 2° C warming will make the world a more impoverished, more violent place, as some assume. Older predictions of “peak oil,” for example, or a “population bomb” have not (yet) come to pass, partly because individuals and institutions responded creatively, on many different scales, to menacing trends.
The new assessment report actually describes the kind of action that would help state and non-state actors confront the challenge of climate change (spoiler alert: it’s not geo-engineering). People are not passive, static victims in the IPCC’s assessment, as they tend to be in reductionist literature. Yet even if the wise policies recommended by the IPCC are ignored, we cannot predict or quantify exactly what the future has in store for humanity.
But now, back to those controversial claims made by climate historians. Critics have accused some of the more ambitious books in climate history – authored by the likes of John Brooke and Geoffrey Parker, for example – of crude determinism for suggesting that past climatic fluctuations on the order of just half a degree Celsius unleashed disaster for societies around the pre-modern world. Indeed, some calamities that climate historians have blamed on climate change had many alternate or additional causes, and most coincided with examples of communities and societies successfully weathering climate change.
Yet the scale of social disruption predicted by the IPCC in a world just a little warmer than our own does invite us to consider whether the fates of pre-industrial societies were not more closely connected to climatic trends than most historians and archaeologists have allowed. Both environments and societies, in other words, seem more vulnerable to even slight climatic fluctuations than we had imagined.
The Popular Response
In the wake of the new report, articles in popular media and discussions in social media have predictably focused on how its findings should be communicated. Should climate communicators try to drum up fear, or should be we inspire hope?
Hope does seem to be more useful emotion in motivation public engagement on global warming. Yet recently, many scholars have actually moved beyond this question. A 2017 article in the journal Nature, for example, concludes that climate change messages should be carefully calibrated to their audience. Neither hope nor fear will motivate everyone; in fact, a catchall message that relies on either emotion will likely provoke the opposite of the desired response in a sizable part of the population. This is hardly surprising: political operatives and advertisers have known for years that the best messages are highly targeted.
Some news articles have stressed what individuals can do in order to lower their personal carbon emissions. Many scientists and environmentalists have responded by arguing that only government policy can begin to address climate change on the scale we need. By stressing personal accountability, some argue, journalists shift attention from the real climate culprits: the big corporations and well-funded political interests with a stake in the fossil fuel economy.
As in most such debates, both sides have valid points. Clearly, we should all aim to limit our emissions while at the same time becoming politically motivated as never before. We will need to fundamentally transform our economy and our politics – quickly! – if we are to confront the challenge of climate change. How we do this, and what it will mean for us personally, is something all of us will need to sort out soon. Those of us who have chosen to remain above the political fray will need to re-evaluate that decision.
Some of the first news articles about the IPCC's new report included commentaries on the need for journalists to make climate change the biggest story they cover. I wrote an article to that effect during the 2016 election, and sent it to the editors of the New York Times. Predictably, there was no response. And now, even in the wake of hurricane Michael’s rapid intensification and calamitous landfall, climate change has already moved off the front pages of many newspapers. Politicians in the United States and elsewhere have already brushed off the IPCC’s urgent warnings.
One wonders: will the new report really change anything? Or will the capitalist dynamics behind our media outlets and political processes derail the changes we so urgently need to make? Ultimately, it’s clear that nobody and nothing will rise to save us from our fate. Those of us who understand the science behind climate change need to do more than communicate. Now, we need to actively be part of the solution. We need to act.
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.
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.
Note: the cover photo was taken by our editor, Benoit Lecavalier, during a recent trip to Greenland.
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.
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.
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.
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.
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.
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.
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.
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?
Contributing Author: Benoit S. Lecavalier
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.
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.
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.
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.
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:
Jonas Bergsøe (Captain)
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.
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.
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.
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.
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.
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.
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?
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.
Note: originally posted on The Otter, blog of the Network in Canadian History and Environment (NiCHE).
On February 10th I embarked on the first leg of a long voyage from Toronto to Goa, a former Portuguese enclave nestled among the beaches of western India. After enduring the concrete monolith that is Frankfurt’s international airport, I finally boarded my second flight and flew south through Turkey, past Syria, across Iran and down towards Mumbai. I left the plane at an hour past midnight. Mosquitos swarming through the airport quickly prompted me to take the malaria medication that would later give me incredibly vivid dreams. Hours later the shock of a violent landing in Goa was nothing compared to the culture shock that followed. As I left the airport and stepped onto the rust-coloured soil I saw signs promoting European luxury vehicles or American cologne towering over slums and endless trash amid lush tropical beauty. After three sunrises and two sunsets without sleep I finally arrived at my hotel, ignoring for the moment the hand-sized spider dangling near my door.
With the help of funding generously provided by Network in Canadian History and Environment (NiCHE), I had travelled nearly 13,000 kilometers to attend the fourth Open Science Meeting (OSM) organized by the Past Global Changes (PAGES) initiative. A core project of the International Geosphere-Biosphere Programme, PAGES has over 5000 subscribing scientists across more than 100 countries. Because research supported by PAGES explores past environments to create a roadmap for the future, the initiative is especially concerned with climate change. Every four years its Open Science Meeting is held in a new location, and in case the Olympic parallels were not obvious enough a “PAGES lamp” was lit at the opening ceremonies. It may not have resembled London’s burning torch, but it did avoid the mishap that embarrassed my fellow Canadians at the Vancouver Olympics.
It’s easy for historians to forget that we don’t have a monopoly over the interpretation of the past. There’s nothing like a scientific conference to remind us that we can only access a tiny sliver of the very recent past, that other disciplines can find voices which speak to the present in sources beyond the documents we hold sacred. Many of the scientists at the OSM reconstructed past climates to measure the significance of modern warming, to unravel how climatic shifts influence different environments, and to provide a clearer picture of the world’s natural history.
In papers and posters scientists presented results derived from the exhaustive analysis of, for example, changes in the growth of trees, the thickness of permanent ice cover and the scope of lakebed deposits. Conclusions were compared with other data that measured shifts in animal ranges, tree lines or glacial extent, all of which can be used to reconstruct changes in regional temperature or precipitation. Evidence from these so-called “proxies” was weighed against a range of sophisticated models, enabling projections of climates past that move seamlessly into the present and future.
Not surprisingly, correlating fluctuations in diverse proxy records and tying them to climatic trends is hardly straightforward. Physicist Ashoka Kumar Sinhvi gave an opening keynote address that exposed the frequently overlooked complexity of linking different kinds of data between different environments at different scales, revealing the limitations of our understanding of past and future climates. Later in the day that concept was echoed by André Berger, who explained how the intricate constellation of influences that shapes the global climate is never stable, complicating the attempt to find historical analogues for our present condition. Sinhvi, Berger and others helped frame the rich data presented in the papers and posters that followed by demonstrating yet again that in science, as in history, the past is opaque, unstable, and forever subject to interpretation.
Of course, that never stops us from seeking more information and, in turn, greater clarity. Some particularly fascinating papers explored past Antarctic climates at a time when the Antarctic Peninsula is warming at a rate of 5.3° C per century. Michael Weber presented findings that reveal how the Antarctic ice sheet is much more reactive to atmospheric Carbon Dioxide than previously believed. Robert Mulvaney then described how the rate of Antarctic melting, unprecedented in the past millennium, likely had analogues in the distant past when ice shelves were entirely absent. Medieval warmth and early modern cooling, familiar to historians of climates past, apparently were not felt in Antarctica. On the other hand, Guillaume Leduc presented exhaustive findings that, while skewed towards the Atlantic region, nevertheless suggested that the “Little Ice Age” between the fourteenth and nineteenth centuries strongly affected global sea surface temperatures. Those results may have critical implications for the nascent field of marine environmental history, which until now has not adequately considered climatic fluctuation.
To unravel histories that bridge culture and nature, environmental historians require some scientific literacy, yet I wasn’t sure what to expect as I prepared to give at a talk at a conference where formulas were ubiquitous and historiography unheard of. I argued that documentary evidence can improve the accuracy of reconstructions of temperature or precipitation, giving us a way of testing meteorological patterns recorded by the kinds of sources unearthed by scientists. Accustomed to the critical analysis of diverse documents, historians are ideally situated to filter documents through the kind of methodology that lets us quantify past weather observations and, in turn, reconstruct the climatic past. Moreover, while tree rings or ice cores rarely provide much more than seasonal resolution, surviving documents can record weather with far greater temporal precision, and some even chart hourly changes.
Most importantly, documentary evidence grants us access to past wind intensity or direction, weather conditions that are less easily measureable through the analysis of scientific proxy data. For centuries it was necessary for European mariners to estimate longitude by calculating a ship’s speed, direction and any leeway in its course, for which the most important influence was wind. Hence many logbooks kept aboard ships abound with reliable and quantifiable meteorological information taken several times on virtually every day of the vessel’s journey. The bulk of my talk presented results from English and Dutch ship logbooks, which suggest that easterly winds increased in the late seventeenth century as the climate cooled across the North Sea.
I was relieved and delighted by the reception I received from the scientists in the audience. More importantly, it was heartening to see the importance of interdisciplinary cooperation in the new “Future Earth” project spearheaded by the International Geosphere-Biosphere Programme. Still, many scholars in both the sciences and the humanities continue to take a passive approach to building connections between disciplines. Conferences like the PAGES OSM have existed for decades, yet many historians fail to realize that their insights are needed and desired. Similarly, most presenters at the upcoming ASEH conference are historians, and scientists or engineers remain underrepresented. Establishing connections between institutions like NiCHE, the ASEH, PAGES and the Climate History Network (CHN) can help move us forward, but what’s even more valuable is feedback from those who have benefitted from conferences in another discipline.
After the conference in Goa I spent a few days in the vast metropolis of Mumbai. My plane was delayed, and as it finally approached the city our pilot was forced to circle the airport for a few minutes before we could land. The slums in Mumbai are so vast that their full extent can only be grasped from the air. As I shifted in my leather seat I glimpsed the innumerable shanties, clustered around open sewage, barely visible through the purple smog. The impoverished people far below, and countless millions like them, will suffer most as our planet continues to warm, yet their voices are never heard in academic or political conferences. The quest to understand climate change must become more inclusive, not just of other academic disciplines, but of all voices, past and present, learned and “unlearned,” rich and poor.
Article originally posted on ActiveHistory.ca.
In recent weeks widespread outrage over the publication of Kate Middleton’s topless photos has existed in strange parallel with a muted response to a shocking acceleration of Arctic melting. While every day brought new stories of royal indignation and litigation to the front pages of major newspapers, concern over the plight of our increasingly topless planet was tucked away in corners of the internet, where many comments were, as ever, skeptical at best. Nevertheless, our destruction or, at least, transformation of the planet’s environment continues despite our apathy and cynicism. This summer Arctic ice cover fell to 3.41 square kilometers, a decline by an area the size of Texas against the previous minimum and some 50% lower than the average between 1979 and 2000. The reasons for enduring public skepticism of climate science and global warming have been examined at length – most eloquently in Naomi Oreskes’ and Eric Conway’s Merchants of Doubt – but the causes for the apathy of believers are less clear.
Upon encountering present-day mysteries our natural inclination as “active” historians is to sift through the past for context and, perhaps, answers. This article proceeds along similar lines, and it is the fourth in a series that explores how historians can shed light on global warming and its consequences. My research unravels relationships between early modern climatic fluctuations and the commercial, military and cultural histories of the Dutch Republic in the seventeenth century. Although those climatic fluctuations were collectively part of a relatively cool climate known as the “Little Ice Age,” average European temperatures during the period could change by nearly 2 degrees Celsius in just a few years. That pales in comparison to the likely scale of future anthropogenic warming, but for historians seeking insight into the climatic shifts we’ve already experienced the Little Ice Age is a great place to look.
The problem is, of course, that most societies within early modern Europe bore little resemblance to our own, and the historical writing we examine to contextualize the present was recorded by observers who frequently perceived weather very differently than we do now. In that alien world the Dutch Republic was unique, a society with capitalist socio-economic structures that seem instantly familiar, and were expressed in everything from remarkable rates of urbanization to incessant financial speculation. Admittedly not many of us are rabid Calvinists or troll the North Sea for herring, but searching the historical record for perfect analogues to ourselves is, of course, impossible. The surviving records kept by the politicians, merchants, farmers and mariners of the Republic provide some of history’s best insights into how we approach a changing climate.
After countless hours spent reading tattered correspondence, water-stained ship logbooks and half-burned diary entries - and thanking the Dutch archival system for its growing commitment to digitalization – a pattern emerges for the weary environmental historian of the Dutch Republic. In the seventeenth century Netherlands, those furthest removed from the environmental necessities of life were least likely to appreciate the importance of weather, even in a country prone to devastating storm floods. Logbooks kept aboard Dutch sailing ships abound with meteorological observation because recording the influence of wind was critical for contemporary navigation. Moreover, the seaworthiness of the vessel, the survival of its stores and the health of its crew were strongly tied to the weather that prevailed during a journey. No surprise, then, that during gales sailors scribbled fearful notes in the margins of their logs, before describing their relief when the weather cleared. Scattered among these reflections are hints that mariners whose work bound them to defined geographic locations perceived changes in patterns of prevailing weather related to shifts in the early modern climate. On the other hand, letters sent by the Republic’s political elite from its many urban centres have limited value for the environmental historian. Johan de Witt, the Republic’s leading political figure in the mid-seventeenth century, was apparently far more concerned about the financial ramifications of the state’s rising debt than even the most severe weather events of his time. To paraphrase Mark Twain, history may not exactly repeat itself, but it does have a tendency to rhyme.
For sailors, such apathy was not an option. The most telling examples of the tension occasionally kindled by these very different attitudes come from the naval wars in which the Republic was embroiled for much of its tenure as a European great power. The weather of the First Anglo-Dutch War was unusually stormy, although the causes were likely unrelated to a broader climatic shift. Fall and winter in the North Sea is almost always tempestuous, but in 1653 the Republic’s situation looked desperate, and in late October the Dutch Admiral – the wonderfully named Witte de With – was still on convoy duty. As he returned to the islands that surrounded the interior waters of the Republic his supplies were low and his crew was mutinous. The Republic’s governing body decided that Witte and his fleet should receive their supplies at sea, to prevent widespread desertion upon arrival at port. In a series of increasingly desperate letters De With begged his superiors to reconsider. Leaving the fleet at sea in the unpredictable and often violent autumn weather was courting suicide, De With insisted, but his masters were unmoved. On November 7th De With’s predictions came to pass when a severe gale sunk eleven warships and drowned some 1,400 seamen.
Historians frequently wrestle with the challenge of creating inclusive histories for societies in which literacy was the privilege of the elite. While those of us who piece together the history of climate frequently use sources that have been overlooked by other historians, we also require the kind of continuous, quantifiable records that were not usually kept by the poor. We may use the logbooks compiled by naval officers where other historians read the correspondence of wealthy merchants, but the reflections of ordinary sailors and dock workers are too often lost to us, as well. Of course, it was often precisely the poor – both urban and rural – whose work and play was most rooted in the unique environment of the Dutch Republic. Consequently, what we do know about, for example, small-scale farmers is intriguing. When the early modern climate cooled and persistent freezing halted travel through the Republic’s many canals, farmers abandoned their boats and used sleds to transport their goods. By switching easily between different modes of transportation, farmers, so attuned to the weather, adapted better than most within the Dutch Republic.
Today, most of us live in concrete jungles that may be oppressed by heat and cold but seem far removed from the environmental consequences of those fluctuations in temperature. A book I recently read about the shipwrecked child of a zookeeper included a passage that, for the environmental historian, provided a thought-provoking summary of the concept of “home.” To the protagonist of Life of Pi, home is a place where the environmental necessities of life, otherwise scattered across a vast geographic expanse, are collected for our convenience. The environmental historian will, of course, note that those environmental resources are not collected but rather connected for our benefit; no food is stored within our urban apartments that did not come from outside. The disastrous droughts of the past summer have reminded some of us that the environmental networks that sustain our urban lives are already strained in the face of an accelerating climatic shift, although many within the American states most affected were likely more impressed with Paul Ryan’s workout regime.
Ultimately, separation from the environments that support us has more to do with our psychology than our geography. As the climate cooled in the late seventeenth century Adriaen van der Goes, a lawyer in The Hague, described weather patterns and their repercussions in vivid letters to his brothers. Neither class nor geography excuses our apathy. Like the politicians who doomed De With’s fleet, we should know better, and, in knowing, we should care.