536

Choosing the worst year in history is a subjective endeavor, despite best efforts. Many of the years on this list could have been just one year in a long string of terrible luck, or even decades in some cases. But, according to Michael McCormick, a Harvard historian specialized in medieval history, people have a single, conclusive answer to the question "what was the worst year in history": 536.

It was the start of a strange fog that engulfed Europe, the Middle East, and significant sections of Asia for an entire 18-month period, causing an almost constant darkening of the sun. Temperatures dropped by much to 2.5 degrees Celsius, ushering in the coldest decade in at least 2,300 years. Summer frost and snow in areas of China and other parts of Asia caused abysmally poor yields and infections, as well as widespread famine in European regions such as Ireland.

As if that weren't enough, a few years later, in 541, whole portions of Europe were struck by the Plague of Justinian, a bubonic plague outbreak named after the Byzantine ruler at the time. One of the deadliest plagues in history, which was made worse by the ongoing Gothic war, the pandemic would end up claiming the lives of over 100 million people across the empire.

While people may never know the exact causes of this period of severe sickness, conflict, and famine, current study shows that a large volcano eruption in Iceland could have been one of the culprits. Whatever the reason, the year 536 would go down in history as the start of one of humanity's darkest periods, and it would be centuries before the worst-affected areas could entirely recover.