History books are full of wars, empires, and revolutions. What you rarely read about in school, though, is the quiet, brutal force lurking behind so many of those stories – a changing climate. It sounds almost too simple. Too geological. Too slow to matter. Yet the evidence keeps piling up, and honestly, once you start seeing it, you can’t unsee it.
The history of the rise and fall of great civilizations has often been closely linked to changing climatic conditions, and that link is justified by the crucial importance of regular agricultural production, which is extremely sensitive to climatic conditions and water availability. Think of it like the foundation of a house. If you weaken the ground beneath it, the whole structure eventually cracks, no matter how grand it looked from the outside.
What makes this even more fascinating is that climate didn’t just erase civilizations directly. It triggered consequences that no one at the time could have predicted. Cascading effects that rewrote maps, reshuffled power, and even changed how humans moved across the planet. So let’s dive into five of the most unexpected ones.
1. Megadroughts Toppled Multiple Empires at Once – Including Ones You’ve Never Heard Of
Here’s something that might genuinely surprise you. Around four thousand years ago, a single massive climate event didn’t just stress one civilization. It brought down several simultaneously across different continents. The 4.2-kiloyear event, a millennial-scale megadrought which took place in Africa and Asia between 5,000 and 4,000 years ago, has been linked with the collapse of the Old Kingdom in Egypt, the Akkadian Empire in Mesopotamia, the Liangzhu culture in the lower Yangtze River area, and the Indus Valley Civilization.
Within 200 years, each of the four major civilizations of this period underwent significant societal transformations, and the extent and nature of these transformations has been widely characterized as collapse events. Think about that for a second. Four sophisticated, geographically separate empires, all struggling and unraveling within roughly the same two-century window. Research suggests that the combined effects of climate change and land mismanagement would lead to shortages of water and food, which may have contributed to social disruption and the collapse of the Akkadian Empire specifically. It wasn’t one bad king. It wasn’t one bad war. It was the sky, essentially, refusing to cooperate.
2. Climate Stress Directly Fueled the Plague of Justinian – And Millions Died
Most people, when they think of the fall of Rome, picture barbarians at the gate. Swords and sieges. What you probably don’t picture is a cooling planet setting the stage for the deadliest outbreak of bubonic plague the ancient world had ever seen. In 536, a major volcanic eruption left a twelve to eighteen month dust veil over the northern hemisphere, leading to environmental cooling and a climate downturn that lasted into the mid-sixth century.
In 541 AD, the first major outbreak of bubonic plague, known as the Plague of Justinian, appeared in Egypt, sweeping through the empire and ravaging the population over eighteen successive waves during a period of 200 years, with total fatalities estimated between twenty and fifty million. I think it’s staggering to sit with that number. Fifty million lives. The Eastern Roman Empire was destabilized when it was stricken by the Plague of Justinian, occurring after a half-decade of abrupt marked cooling. The cold didn’t cause the plague directly. It weakened harvests, weakened bodies, and created the exact conditions where disease could run wild and unchecked.
3. The Little Ice Age Didn’t Just Freeze Rivers – It Triggered the French Revolution
This one genuinely floors people when they first hear it. You might know that the Little Ice Age made European winters brutally cold between roughly the 14th and 19th centuries. What you probably didn’t know is that those frozen winters had a direct hand in toppling one of Europe’s most powerful monarchies. Around 1770, a particularly cold period began in Europe, devastating agricultural production, and in 1775, severe grain shortages in France caused by successive years of poor harvests triggered bread riots throughout the kingdom.
The years of climatic stress, financial instability, and political conflict brutally coalesced in 1788 and 1789, and a severe drought in the spring of 1788 devastated staple crops, leaving them crippled and withered. By the following winter, hunger was widespread and patience had run out entirely. Climate change primarily affected people’s livelihoods by reducing harvests, lowering food-resource availability, and sharply increasing cereal prices – playing a major role in heightening population vulnerability through malnutrition, which in turn fuelled social anger towards political authorities for failing to mitigate the impact of climate change. The guillotine, in a very real sense, had a meteorological origin.
4. Climate-Driven Mass Migration Reshaped the Ancient World’s Demographics
When the land stops producing food, people leave. That seems obvious. What’s less obvious is how profoundly those movements reshuffled the entire ethnic, cultural, and political makeup of vast regions. It’s not just people moving from point A to point B. It’s a chain reaction. When the effects of drought began to be felt, people would leave the stricken areas and migrate to more abundant ones, but these mass migration events increased the pressure on remaining resources, leading to yet more problems.
Climate change has been linked to human migration from as early as the end of the Pleistocene to the early twenty-first century, with the effect of climate on available resources and living conditions such as food, water, and temperature driving the movement of populations and determining the ability for groups to begin a system of agriculture or continue a foraging lifestyle. The Harappan civilization of the Indus Valley offers a particularly haunting example. Around 3,800 years ago the Harappan civilization began to crumble, and by 3,000 years ago it was gone, with archaeologists turning up no evidence of a major war or epidemic, earthquake, or catastrophic flood. No armies. No volcanoes. Just a weakening monsoon, crops that stopped growing, and a people quietly dispersing across a subcontinent.
5. The Little Ice Age Accidentally Sparked a Century of Almost Constant Warfare in Europe
Let’s be real – most of us assume wars happen because of ideology, ambition, or revenge. And yes, those things matter. Still, the historical record of the 17th century tells a darker, stranger story. On the European continent in the 17th century, only three years (1610, 1670, and 1682) were free from interstate wars. Three years. Out of one hundred.
Pockmarked with wars, inflation, famines, and even shrinking human bodies, the 1600s in Europe came to be called the General Crisis, and whereas historians had blamed those tumultuous decades on the growing pains between feudalism and capitalism, research points to another culprit: the coldest stretch of the climate change period known as the Little Ice Age. The connection is more direct than you’d think. From the late 16th century on, winters were longer and colder than previously, and the summers were shorter, wetter, and colder, causing famines as the result of failed harvests, intensifying the fight for resources, and driving violent conflict that was largely coded in religious terms, with people believing that God was angry. Religion became the language of the crisis, but the crisis itself had roots in the soil – or rather, in the frozen, unproductive lack of it.
Conclusion: What History’s Climate Crises Are Really Telling You
There’s a thread running through every one of these stories, and it’s worth pausing on. Climate shifts didn’t always destroy civilizations by direct force. They worked more like a slow leak in a boat – manageable at first, then catastrophic all at once. Prehistorical and historical data demonstrate that societal collapse rarely has a single cause but is often due to many biophysical and socio-economic stressors, including climate, overexploitation of resources, and societal conflicts.
Research suggests that a stable society can withstand even a dramatic climate shock, whereas a small shock can lead to chaos in a vulnerable one. That’s the part that should make you think. It’s not just the severity of the climate event. It’s the resilience, or lack of it, of the society facing it.
The Akkadian Empire, the Harappans, the Maya, the empires caught in the grip of the Little Ice Age – none of them saw it coming the way we now can. The challenge facing our world due to unprecedented, man-made climate change is something that should not be underestimated, but unlike these ancient civilizations, we are in a position to do something about it. That’s either the most hopeful sentence in this entire piece, or the most sobering, depending on what you think happens next.
What would you have guessed was the biggest driver of human history – ambition, religion, economics, or the weather? The answer, it turns out, might be all four at once. Tell us your thoughts in the comments below.
