What Was The Worst Year In Human History?

A painting capturing a civilization in chaos during the winter of 536 CE.

What was the worst year in human history? That is a very contested and subjective question asked among historians. Some point to 1918, when World War I ended after claiming 20 million lives, and the Spanish Flu claimed another 50 to 100 million. Meanwhile, others point to even as recently as 2020, when the COVID-19 pandemic spread across the world. These years undoubtedly hit society hard, and although it’s possible to argue that a year like 2020 or 1918 was the “worst” year, there’s actually a strong case for another year: 536 CE. This year didn’t just bring one disaster; rather, it set off a dark chain of events that affected millions of lives across continents. Though evidence may not be as concrete for 536 as for more recent years like 2020 or 1918, we still have plenty of supporting proof from ancient texts, tree ring data, and archaeological findings that back up the claim that the year 536 was the worst of all.

As opposed to most other contenders for the worst year in human history, the year 536 was not marked with war, disease, or political turmoil. In fact, it began rather normally until a strange event took place that puzzled people around the world. A thick fog settled over the ground, effectively blocking out the sun for months. The Roman historian Procopius, who had lived through these odd months, wrote, “It seemed as though the sun had lost its light, and it no longer shone with the brilliance of day, but rather as the moon, without rays or warmth, for more than a year.” Meanwhile, Cassiodorus, a Roman official, who had also happened to live through them, described, “The sunlight was weak, the sky appeared colorless, the cold pierced to the bone, and it was as if summer had been defeated by winter.” Though they might seem like it, these accounts weren’t exaggerated. By analyzing tree rings from old trees, scientists found evidence that was in agreement with the historical accounts from Procopius and Cassiodorus. In the parts of the tree rings that coincided with 536, scientists saw indications that something had blocked sunlight across the Northern Hemisphere, causing a dramatic drop in temperatures. 

But where exactly had this mysterious fog actually come from? The exact source still remains debated, but it’s highly likely that it originated from a massive volcanic eruption. The location of this eruption, if it even happened in the first place, also remains unknown, but wherever it may have been, one thing is clear: the eruption must have thrown enormous amounts of ash and particles into the atmosphere, creating a veil that dimmed the sun. Temperatures dropped by as much as 2.5°C (4.5°F) in many areas, a significant shift for a world dependent on agriculture. According to tree ring data, the winter of 536 was the coldest in over 2,000 years. Crops that needed warmth and sunlight died off, and the growing season shrank. Places like Ireland, Syria, and the Byzantine Empire saw harvests dwindle or disappear entirely, and without enough food, people faced starvation. Eventually, societies that relied solely on stable harvests began to fail.

The famine and starvation hit hardest in the regions already stretched thin. In Europe, communities that depended on wheat and barley couldn’t produce enough to feed their people, while in Asia, rice fields suffered as the cold disrupted planting and growth cycles. Chinese historical records describe snow falling in early summer, which is an unheard-of event that signaled deeper trouble. Thousands of families went hungry, and entire villages were abandoned as people searched for food. The Byzantine Empire, a major power at the time, saw its agricultural systems collapse, leaving cities like Constantinople struggling to feed their populations. Trade networks, which moved food and goods across regions, slowed down as well when supplies dried up.

A drawing showing people suffering from the Justinianic Plague during its outbreak in 541 CE.

As if the cold and hunger weren’t enough, the climate shift also set the stage for an even deadlier disaster. By 541, just five years after the fog first appeared, a plague, called the Justinianic Plague, swept through the Mediterranean and beyond. This outbreak was caused by the bacterium Yersinia pestis, carried by fleas on rats. The cold and famine during 536 had driven rats out of their usual hiding places, forcing them to go and search for food in human settlements. The malnutrition caused by famine had also weakened people’s immune systems, making them more vulnerable to disease. The fleas, feeding on infected rats, spread the plague to humans, who had little resistance to the illness, and the results were devastating. Estimates suggest the plague killed between 30 and 50 million people, which translates to roughly half the population of the Byzantine Empire. Entire communities were wiped out, and cities like Constantinople became ghost towns as bodies piled up faster than they could be buried. Although it’s not right to pin all the blame for the impacts of the plague on the year 536, it certainly played a significant, albeit indirect, role in creating the outbreak a few years later.

Comparing 536 to other catastrophic years like 1918 or 2020 helps put its scale into perspective. The Spanish flu in 1918 killed millions, but it came at the end of a war, and recovery began relatively quickly as vaccines and medical care improved. In 2020, COVID-19 caused global lockdowns, but  again, modern technology, like vaccines and communication networks, helped us adapt relatively quickly. In contrast, there was no such relief in 536. People had no understanding of volcanic ash, famine, or bacteria; they had no way to predict when the fog would lift or how its effects would lead to a plague outbreak in the future. The tools we have right now to fight back and push through, such as science, medicine, and global coordination, pretty much didn’t exist back then. The crises of 536 piled on top of each other, each one making the next worse, with no clear end in sight for those living through it.

Some might argue that other years rival 536 for the title of worst in history. The Black Death in 1347 killed a similar percentage of Europe’s population, perhaps 50 percent in some areas, and its effects lingered for generations. Yet, it lacked the global climate shift that made 536 so unique. The Mongol invasions of the 13th century caused millions of deaths and reshaped empires, but they were spread over decades, not concentrated in a single year. Even the 20th century’s world wars, with their staggering death tolls, came with moments of hope, like armistices or rebuilding efforts. In 536, the disasters felt relentless, with no immediate recovery on the horizon. The fog, the cold, the famine, and the eventual plague created a perfect storm that left societies reeling.

Simply put, the peculiar, widespread, and long-term impacts of 536 are why it stands out. As we saw, the Byzantine Empire never fully regained its strength, and the power vacuum in Europe allowed smaller, fragmented kingdoms to rise. Looking eastward, in places like Asia, the climate shift disrupted dynasties, with some Chinese records noting political instability tied to food shortages. Even in the Americas, where written records from the time are scarce, archaeological evidence suggests that civilizations like the Maya faced environmental stress around this period, possibly linked to the same volcanic activity. Unlike years such as 1918 or 2020, human society felt the effects of the year 536 CE for much longer, and worst of all, the problems were caused in the most unpredictable way: an eerie worldwide fog composed of volcanic ash.