How the weather shapes history
Throughout the ages, climate change has had profound – and sometimes devastating – consequences for human civilisation.
By Jerome Roos
Frozen: a display at London's Natural History Museum illustrating the ice sheet that moved over Scotland around 670 million years ago. Image by Natural History Museum, London / Bridgeman Images
William Shakespeare paid close attention to the weather. From the stormy climax of King Lear to the thunder, lightning and rain in Macbeth, the great playwright often invoked atmospheric disturbances to convey a sense of dread or disorder. In A Midsummer Night's Dream, he alludes to a particularly unnerving development. "The seasons alter," Titania remarks: "The spring, the summer, the childing autumn, angry winter, change their wonted liveries, and the mazed world, by their increase, now knows not which is which."
For Shakespeare and his contemporaries, living through a period of sharp global cooling known as the Little Ice Age, the altering of the seasons was an unmistakable fact of life. Temperatures had been dropping ever since the 1560s. Fierce winters and violent summer storms now left regular harvest failures in their wake. As the agrarian expansion of the 16th century slowly gave way to the recession of the 17th, a wave of poverty washed over the countryside. It would not be long before revolution and civil war tore through the ­British Isles. For the Bard of Avon, the unpredictability of the weather was much more than a poetic metaphor: it was a material force to be reckoned with in its own right.
The present generation is not the first to be confronted with the threat of catastrophic climate change. Although anthropogenic greenhouse gas emissions are driving an unprecedented increase in atmospheric CO2 concentrations, recent advances in climate science have revealed a long-standing struggle with the elements. Before our early hominid ancestors learned to speak or even to walk upright, climate change was already shaping the evolutionary trajectory of our species, spurring on the development of bigger brains and the use of more complex tools. No wonder that scientists have referred to climatic variability as the "midwife of humanity".
The first anatomically modern humans emerged in Africa around 200,000 years ago, following millions of years of adaptation to ever-changing climatic conditions. Their descendants would remain locked in this "reign of chaos" for generations to come. Exposed to the bitter cold of recurring ice ages, the small bands of Palaeolithic hunter-gatherers that ventured out of Africa at this time were repeatedly wiped out by bouts of climate-induced scarcity and disease.
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On several occasions, humanity came close to extinction: a gargantuan supervolcano eruption some 70,000 years ago unleashed a spell of global cooling so extreme that it may have reduced the world population to only 1,000 breeding pairs. Our prehistoric ­ancestors proved resilient in the face of such calamities, but it is clear that their world was far from a peaceful Garden of Eden.
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Then, a little more than 10,000 years ago, something began to change: the Earth's climate suddenly grew more temperate. The ice receded and the violent swings that characterised the Pleistocene eventually came to an end. As temperatures stabilised, a new interglacial equilibrium emerged, giving birth to the relatively steady and benign climate of the Holocene. Everything we now associate with human civilisation – agriculture, cities, writing, money, technology, divisions of labour, systems of government – arose within this uniquely sheltered environment. As David Attenborough recently pointed out in his address at the Cop26 meeting in Glasgow, "the global temperature has not wavered in this period by more than plus or minus 1 degree Celsius".
Until today, that is. Over the past 200 years, the triumph of industrial capitalism and the advent of the modern fossil-fuel economy have radically reshaped humanity's relationship with its natural environment. In two short centuries – a mere blip in evolutionary terms – the fragile chemical balance underpinning the climatic stability of the Holocene was thoroughly upset. Atmospheric concentrations of CO2 skyrocketed from around 283 parts per million at the start of the industrial era to more than 412 parts per million today. The last time CO2 levels were this elevated was at the height of the Pliocene hothouse four million years ago. The sudden jolt in emissions has already driven global temperatures up by 1 degree Celsius, with the world on course for 2.4 to 2.7 degrees of heating by 2100.
We now find ourselves in a new epoch, variously referred to as the Anthropocene or the Capitalocene, denoting an unparalleled age in which human activities – or capitalist production processes – are altering the very composition of the Earth's atmosphere. Scientists continue to warn us that the resultant climate impacts are already multiplying and intensifying extreme ­weather events.
Yet government action to wean the world off fossil fuels continues to fall hopelessly short. In this context, an urgent question imposes itself: what do these developments mean for the future of civilisation? While long-term projections remain fraught with complexity, ongoing research on past climatic shifts is already beginning to yield disturbing new answers.
How do complex societies respond to the ecological challenges posed by their climate? For a long time, we simply had no idea. Wary of being dismissed as environmental determinists, 20th-century scholars were generally hesitant to take on the question. There were some notable exceptions, of course, such as the great French historian Fernand Braudel, who recognised the importance of climate in his monumental works on the origins of capitalism and civilisation. But when ­Emmanuel Le Roy Ladurie – ­Braudel's prominent protégé – wrote a pioneering study on the subject in 1967, he still felt impelled to conclude: "In the long term, the human consequences of climate seem to be slight, perhaps negligible."
Today, this view is being overturned by the findings of a burgeoning new body of research. Driven by rising ecological awareness, and informed by rapid advances in our understanding of past climatic conditions, scholars are beginning to recognise that even the relatively stable environment of the ­Holocene was regularly punctuated by ­alternating phases of warming and cooling. New studies are now linking these temperature fluctuations to a number of important historical developments: from the rise and fall of ancient civilisations to a sequence of global crises that profoundly shaped our modern world.
The findings emerging from this new body of research offer a salutary warning: notwithstanding the remarkable biological and cultural resilience of our species, the historical record shows that even minor changes in temperature and precipitation can have far-reaching societal repercussions.
Here, the experience of the first human civilisations may offer a distant mirror to our own. Starting with the onset of the Bronze Age around 5,000 years ago, complex urban societies suddenly began to appear in a more or less synchronised development around the globe. In the Old World, cities and states emerged along the Nile, Tigris, Euphrates, Indus and Yellow rivers. At the same time, major civilisations flourished in Mesoamerica and coastal Peru. The historian John L Brooke has argued that the strikingly similar patterns of social change in these distant regions were shaped "by a common global experience of long stretches of relatively ­stable climate optimum – and then roughly simultaneous abrupt climate change".
The first such episode of abrupt climate change took place around 4,200 years ago. In one of the most extreme climatic events of the Holocene, a century-long mega-drought brought widespread aridification to the previously verdant lands of Egypt, Mesopotamia and the Indus Valley, while at the same time submerging China and Peru under floodwater, provoking the collapse of some of the first great river valley civilisations. In Egypt, green fields that had once teemed with fresh produce were swallowed by the advancing desert; sprawling cities and vast temple complexes were left buried under layers of dust and sand.
It would not be the last time that climate change wreaked havoc on human progress. Recent research has unveiled a similar pattern at work in the second wave civilisations of classical antiquity. Again, an element of synchronicity appears to have been at play, exemplified by the more or less simultaneous rise of powerful empires in Han China and ancient Rome. Thanks to scientific analyses of ice cores, tree rings and sediment layers, we now know that the spectacular expansion of these classical civilisations was facilitated by a prolonged climatic optimum, known as the Roman Warm Period, which brought warmer and wetter conditions to parts of Eurasia. Buoyed by reliable rainfall and abundant grain harvests, the Romans were able to build up an empire of unprecedented size and splendour.
But then, after 150 AD, climatic conditions again deteriorated. Temperatures fell and the weather became more unpredictable. In a recent study, the classicist Kyle Harper details how this climate shift played an important and long overlooked role in Rome's eventual demise in the fifth century. In the 530s and 540s, a burst of volcanic activity dealt a decisive final blow, instigating a 150-year cold period marked by the lowest temperatures on record for thousands of years. Pope Gregory the Great observed "novelties in the atmosphere, terrors in the sky, and storms out of their orderly seasons". In AD 541, the remnants of the Roman empire were struck by a devastating outbreak of bubonic plague that wiped out as much as half of the population. The era of classical antiquity was at an end.
Contemporaries seem to have been aware of at least some of these developments. In the third century, Cyprian, the bishop of Carthage, wrote that, "The falling rays of the setting sun are not so bright or brilliantly fiery… The fountain that once overflowed from abundant springs, now forsaken by old age, scarcely yields a drop." While such statements would previously have been dismissed as metaphorical, recent advances in climate science recast them in a different light. Solar forcing did cause the rays of the sun to grow weaker at this time, while reduced rainfall meant that many springs in the Mediterranean basin would have run dry. As Harper notes, "Cyprian was probably right to sense the chill winds of a cooler age in the middle of the third century."
We cannot reduce the complexity of Rome's epochal downfall to a single factor such as climate change: the process of imperial decline was multifaceted, with various elements interacting in intricate and still poorly understood ways. It is clear, however, that internal weaknesses and external military threats worked in tandem with environmental stresses and recurring pandemic disease to steadily sap the empire's vitality. "The fate of Rome was played out by emperors and barbarians, senators and generals, soldiers and slaves," Harper underlines. "But it was equally decided by bacteria and viruses, volcanoes and solar cycles."
While climate change played an important role in the demise of some of the best-known ancient civilisations, its historical significance did not end there. Over the past decade, historians have also become more aware of the ways in which recurring episodes of climatic instability continued to plague the more advanced societies of the late-medieval and early-modern periods. The findings of this research show how several brief pulses of colder weather – associated with the so-called Little Ice Age – gave rise to major environmental disasters and severe political turmoil across large parts of the globe.
Take the Black Death of 1346-53, universally acknowledged to have been one of the deadliest pandemics in recorded history. Killing between 40 and 60 per cent of the European population, the medieval plague outbreak led to long-term labour shortages that thoroughly undermined the viability of Europe's ailing feudal order.
That the Black Death was a major turning point in the transition to capitalism is beyond doubt, but historians have only recently begun to recognise the ways in which the pandemic may have been related to the end of the Medieval Warm Period and the first pangs of the Little Ice Age. If the classical era was bookended by climate chaos and pandemic disease, so were the Middle Ages.
It was not until Shakespeare's day, however, that the extreme cold of the Little Ice Age really began to make itself felt. Starting in the 1560s, temperatures in the Northern Hemisphere fell to their lowest levels in the past millennium, reaching their nadir during the tumultuous 17th century. Although the temperature changes involved were not very large by today's standards, their effects were noticeable. Europe's winters, in particular, grew unusually frigid. The River Thames repeatedly froze over, enabling enterprising Londoners to hold regular frost fairs on the ice. In 1621, the inhabitants of Istanbul were able to walk from Europe to Asia over the frozen Bosporus. The new winter scenery left an indelible impression on the Dutch masters as well, resulting in such iconic paintings as ­Pieter Bruegel the Elder's Hunters in the Snow (1565) and Hendrick Avercamp's Winter Landscape with Skaters (circa 1608).
The causes of the Little Ice Age are still debated, but they seem to have involved some combination of orbital forcing, solar variability and volcanic eruptions. What is certain, however, is that the sudden change in climate had far-reaching consequences. In 1614, the Swiss botanist Renward Cysat decided to keep track of these developments in a chronicle, since "the past few years have seen such a strange and wondrous succession of changes in the weather". He observed that "for some time now the years have shown themselves to be more rigorous and severe in the recent past, and we have seen deterioration amongst living things, not only among mankind and the animal world but also in the earth's crops and produce".
Harvest failures became more frequent and a deep economic recession took hold. The historian Geoffrey Parker has recently linked these difficulties to the dramatic political disorders that beset large parts of the world during the "general crisis" of the 17th century. Intense conflict erupted all over Europe: Germany was torn apart by the Thirty Years' War; France was blighted by civil wars known as the Fronde; King Charles I was beheaded in the English Civil War; and the Spanish empire lost the Netherlands and Portugal to revolts. At the same time, the Ottoman empire was rocked by military insurgencies and the murder of the sultan, Russia went through its Time of Troubles, and the Ming dynasty was overthrown in China, creating an opening for the Manchu armies to invade and establish foreign rule.
Contemporaries seemed to believe that they were living through a uniquely troubled time. In 1641, a country gazetteer in China wrote: "Among all the strange occurrences of disaster and rebellion, there had never been anything worse than this." On the other side of the world, in 1643, the English Puritan clergyman Jeremiah Whitaker declared in a sermon: "[These] days are days of shaking and this shaking is universal: the Palatinate, Bohemia, Germany, Catalonia, Portugal, Ireland, England." That same year, a Spanish pamphleteer came to a similar conclusion, writing that, "This seems to be one of the epochs in which every nation is turned upside down, leading some great minds to suspect that we are approaching the end of the world." The civil war in England famously inspired Thomas Hobbes to develop his case for absolute rule in Leviathan (1651). Hobbes' image of the state of nature as a brutal war of all against all, in which life is "solitary, poor, nasty, brutish and short," was derived in part from his experience of the 17th-century crisis.
Although the weather eventually improved and the crisis finally eased towards the end of the 17th century, the Little Ice Age made an unexpected comeback on the eve of the French Revolution. Its effects were amplified by a huge volcanic eruption in Iceland, which spewed sulphur dioxide into the atmosphere in 1783 and 1784. According to the 18th-century British naturalist Gilbert White, the eruption blanketed the sky in a "smokey fog" and left the sun looking "as blank as a clouded moon". This solar dimming produced a drop in temperatures and years of extreme weather that led to repeated harvest failures across Europe.
In France, already plagued by a host of financial problems, the consequences were especially severe. "The country is a heap of ashes," the future US president John Adams wrote during a visit in 1785. "Grass is scarcely to be seen and all sorts of grain is short, thin, pale, and feeble. . . I pity these people from my soul. There is at this moment as little appearance of a change of weather as ever."
Three years later, Thomas Jefferson, then the US envoy to France, reported a "winter of such severe cold, as was without example in the memory of man. . . All outdoor labour was suspended, and the poor, without the wages of labour were, of course, without either bread or fuel." The high price of bread stoked the embers of popular discontent and directly fed into the revolutionary fervour that would culminate in the beheading of Louis XVI and the overthrow of the ancien régime.
[See also: Why a commitment to justice is not an optional extra in tackling the climate crisis]
We can no longer ignore the central role that climate change has played in the great drama of human history. From the "reign of chaos" during the Pleistocene to the "hoary-headed frosts" of Shakespeare's day, our world has been shaped by the vagaries of the weather. While climate denialists often invoke such observations to play down the threat of anthropogenic climate change in our own time, this is exactly the wrong conclusion to draw. If history teaches us anything, it is that even minor changes in temperature and precipitation can have catastrophic consequences for human civilisation.
Even then, however, we should avoid the temptation to fall for simplistic historical analogies between past civilisational collapse and present-day ecological challenges. Historical research shows that complex social systems tend to respond to climate shocks in unpredictable, non-linear ways. While an economically strained and internally divided society, such as pre-revolutionary France, can easily be tipped into debilitating political conflict, a resilient and egalitarian society may be able to survive similar stresses by adapting to its changed environment. In the 17th century, Japan and the Netherlands managed to thrive even as the Little Ice Age was at its height. Climate need not be fate.
What makes our era of anthropogenic climate change unique is that, this time around, world leaders actually hold the future of civilisation in their own hands. Scientists agree that it is still possible to avoid the worst effects of climate breakdown by keeping temperature rises limited to 1.5 degrees Celsius. History merely offers us a warning of what could happen if they fail.
Jerome Roos is a fellow in international political economy at the London School of Economics and Political Science
This article appears in the 24 Nov 2021 issue of the New Statesman, The Agent of Chaos
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