In 536 AD, people across Europe, the Mediterranean, and Asia looked up to find the sun shining with the pale, weak brightness of the moon. Shadows lost their sharpness, summer temperatures collapsed, and crops struggled beneath a strange, persistent haze. No one knew why. There had been no warning, and for all anyone understood, the sun itself appeared to be dying.
The Byzantine historian Procopius wrote that the sun gave off light without brightness, almost like an eclipse, and that the phenomenon lasted for the entire year. The Roman statesman Cassiodorus described a bluish sun, a moon without normal brilliance, and midday shadows that could barely be seen. Irish annals recorded failures of bread, while Chinese sources preserved accounts of severe weather and summer snow. Nobody at the time understood the cause, but modern science has an answer.
Ice cores preserve layers of sulfate from ancient eruptions, and tree rings record years when cold restricted growth. Together, they reveal a major volcanic eruption in 536, followed by an even larger eruption around 540, and another volcanic signal later in the decade. The eruptions blasted sulfur-bearing gases high into the atmosphere, where they formed tiny aerosols that reflected part of the sun’s energy back into space. European summer temperatures may have fallen by roughly 1.
5 to 2. 5 degrees Celsius in 536, a seemingly small shift that proved catastrophic for pre-industrial farming. A few degrees can shorten growing seasons, delay flowering, and bring frost when crops are vulnerable. Most people in the ancient world lived close to the annual harvest, with no reserves and no emergency supply chains.
When weather destroyed the grain, families ate their seed grain, then their working animals, then anything that could be called food. Hunger rarely arrives as one dramatic moment. It is subtraction. Bread becomes smaller, prices rise, families sell tools and land, children stop growing normally, and weakened bodies become easier targets for infection.
Tree ring evidence shows that the eruption helped trigger the coldest decade in at least 2,000 years. Then, around 540, another enormous eruption injected more material into the atmosphere, renewing the cooling just as communities desperately needed stability. The crisis was not one disaster but a trap with stages: first the dimming, then crop failure and famine, then another eruption, then plague. In 541, a new epidemic was reported at Pelusium in Egypt.
It moved through the Eastern Roman Empire and beyond, caused by Yersinia pestis, the same bacterium associated with the later Black Death. In 542, it struck Constantinople, one of the largest cities in the world. Procopius described fever, swellings in the groin or armpit, confusion, delirium, and death, claiming that normal burial systems failed as bodies were placed in mass graves. Ancient DNA has confirmed the presence of Yersinia pestis in remains from the first plague pandemic.
However, modern scholars debate the true death toll, as evidence varies dramatically by region, and the empire did not instantly collapse. Emperor Justinian continued ruling until 565, armies kept fighting, taxes were collected, and cities continued to function even while large numbers of people suffered inside them. Nowhere was the suffering more concentrated than in Italy, where climate disaster and disease arrived during the Gothic War. Justinian’s forces were attempting to reconquer the peninsula, and cities were besieged, farms were destroyed, and armies seized food.
For civilians trapped there in the 540s, the distinction between an empire surviving and an empire collapsing would have felt purely academic. Move forward to 1348, and the sun is visible again. That is almost the only advantage. The 14th century had already opened badly with the Great Famine of 1315 to 1317, when relentless rain and cold destroyed harvests across much of Northern Europe, soaring food prices, and leaving millions malnourished for years.
Then, in the late 1340s, plague arrived from central Eurasia along trade routes, reaching the Black Sea and Mediterranean ports before spreading with terrifying speed through Europe, North Africa, and Western Asia. In a European town, the first sign might be rumor. Then someone on your street develops fever, painful swellings appear in the groin, neck, or armpit, and a healthy person can become desperately ill and die within days. There are no antibiotics, no knowledge of bacteria, and no agreement about what carries the disease.
People blame corrupted air, planetary alignments, divine anger, foreigners, or minority communities. Some flee, potentially taking the infection with them, while violence erupts against Jewish communities falsely accused of poisoning wells. Between 1347 and 1353, the Black Death may have killed around 30 to 60 percent of Europe’s population, with enormous regional variation. In the worst-hit places, entire households disappeared, clergy died caring for the sick, and fields went unharvested because the workers were dead.
If half the people around you vanished within a few years, death would stop being an exceptional event. It would become the background of life. But Europe is not the world. For indigenous peoples in the Americas, the catastrophic period begins after 1492.
European arrival connected populations that had been separated for thousands of years, introducing smallpox, measles, influenza, and other infections to communities with no previous exposure. Epidemics interacted with warfare, enslavement, forced labor, displacement, famine, and colonial violence. Population losses were immense, but they did not occur in an empty landscape. They arrived inside conquest.
For many communities, the disaster was more than mortality. It was the destruction of political systems, sacred sites, languages, family networks, and control over ancestral land. Central Europe during the Thirty Years’ War, from 1618 to 1648, offers another contender. For civilians in heavily affected German regions, war meant armies repeatedly moving across the landscape and surviving by extracting resources from the places they occupied.
Troops requisitioned food, then stole it, then destroyed what they could not carry. Villages faced violence from enemy soldiers, friendly soldiers, deserters, and bandits. Farms were abandoned, trade broke down, and refugees crowded into towns. Most deaths were not caused on battlefields but through the familiar partnership of hunger, infection, and social collapse.
A protected city might survive, while a village along a military route could be looted repeatedly until nothing remained. In April 1815, Mount Tambora in present-day Indonesia produced one of the largest eruptions in recorded history, killing tens of thousands directly and altering climate far beyond its shores. In 1816, the so-called year without a summer, cold and erratic weather damaged crops across parts of Europe and North America, frost struck during months that should have supported growth, and food prices rose sharply. The resemblance to 536 is obvious, but 19th-century societies had wider trade networks, newspapers, and governments capable of organizing at least some relief.
In 536, people could not know whether the failed harvest was local or continental. They could only look at the sky. The 20th century, meanwhile, supplies horrors of deliberate cruelty that no historical ranking can meaningfully compare. Trenches in 1916, the influenza pandemic of 1918, famine in Ukraine, the Holocaust, Hiroshima, and countless other wartime and engineered catastrophes were undeniably worse for the people trapped inside them.
Modern states gained the power to concentrate suffering deliberately, registering populations, controlling transport, weaponizing food, and industrializing killing. Ancient disasters often reveal human helplessness before nature. Modern atrocities reveal what humans can accomplish once extremely organized. Could prehistory contain an even worse period?
Possibly. Around 74,000 years ago, the Toba super-eruption released enormous quantities of material, and it was once proposed that it nearly drove humans to extinction. That dramatic claim is now heavily debated, as evidence from Africa suggests human populations did not all suffer one uniform near-extinction event. The eruption was immense, but the simple story of a global human population collapsing to a few thousand is not established.
Prehistory creates a frustrating possibility: the worst time may have left too few witnesses to describe it. So return to 536. Imagine you are an ordinary farmer somewhere in a badly affected part of the northern hemisphere. The spring is cold.
You plant anyway, because refusing to plant guarantees hunger while planting merely makes it likely. The sun rises behind a veil, days pass without normal warmth, and growth is slow. By late summer, the grain is thin. You save what you can.
There is no scientific explanation. Perhaps God is angry. Perhaps the end of the world is beginning. Every explanation is terrifying because none produces food.
Winter consumes the harvest. The next year begins with fewer animals and less seed. Neighbors leave. Travelers report that other places are suffering too.
Prices rise. Children are especially vulnerable, and minor infections become dangerous because hunger has reduced the body’s reserves. Then the climate remains unstable. Around 540, the sky receives another volcanic injection, and soon rumors arrive of disease in distant ports.
Then the disease is no longer distant. If forced to select one calendar year with broad environmental reach, 536 deserves the title of the worst year to be alive. It abruptly darkened skies across widely separated regions, helped trigger major cooling, damaged harvests, and began a decade of extraordinary climatic hardship. It attacked the foundation beneath almost every pre-industrial society: sunlight becoming food.
But if the measure is immediate probability of death in a heavily affected population, 1348 may be worse. If the measure is destruction of a people’s sovereignty and world, the decades after European contact in the Americas may be worse. If the measure is civilian exposure to war, famine, and disease combined, parts of central Europe during the Thirty Years’ War may be worse. History refuses to give one clean winner because suffering is local, even when disaster is global.
Still, 536 has one uniquely disturbing quality. There was no enemy to defeat, no wall to stop the atmosphere, no treaty to restore sunlight, and no ruler who could command summer to return. Somewhere, thousands of kilometers away, a volcano had exploded. Its gases rose beyond sight, crossed borders that did not yet exist, and altered seasons for people who would never know the volcano’s name.
The cause was invisible. The hunger was not. Then, before recovery, the world delivered another eruption and a pandemic. The worst part was that the year ended.
The crisis did not.