536 AD: the never-ending winter of the worst year in history

If you ask medieval historian Michael McCormick of the University of Harvard what year was the worst to be alive, and he’s got an answer. Not 1349, when the Black Death wiped out half of Europe, and not 1918, when “spanish” flu killed 50 million to 100 million people. It happened to everyone, sooner or later, to hope that a particularly difficult year will come to an end, hoping that the next one will reserve better days. But what was, objectively, the worst year in human history? It seems impossible to give an answer, because humanity has always had to deal with innumerable catastrophes, natural but not only.
McCormick states that the 536 AD was by far the worst year for planet Earth and its inhabitants: in Europe, “It was the beginning of one of the worst periods to be alive, if not the worst year,” he says.
However, in that dramatic 536 more lethal pestilences than usual had not spread, nor were particularly bloody wars fought. So why did the historian come to this conclusion?

The disaster came from the sky, in the form of a mysterious fog that plunged Europe, the Middle East, and parts of Asia into darkness, day and night—for 18 months, “For the sun gave forth its light without brightness, like the moon, during the whole year,” wrote Byzantine historian Procopius.
Temperatures in the summer of that year fell 1.5°C to 2.5°C, initiating the coldest decade in the past 2300 years.
“… From March 24th of this year until June 24th of the following year … the winter was severe, so much so that from the large and unusual amount of snow the birds perished … (Zechariah of Mytilene – Chronicle)”.
A year without sun then, a very long winter that caused famines a bit everywhere: snow fell that summer in China, crops failed and people starved. The Irish chronicles recorded “a failure of bread from the years 536–539.”
But, how had that impenetrable blanket of fog formed?

Historians have long known that for some time that around the middle of the sixth century there was a period of darkness, but what caused it remained a mystery. In the 90s some studies on tree rings suggested that around the middle of the 500 AD the summers had been unusually cold. A search of three years ago discovered in the ice of Antarctica the traces of a violent volcanic eruption, which occurred between the end of 535 and the beginning of 536. Scholars hypothesized that it had taken place in North America.
Instead, an ultraprecise analysis of ice that over the centuries has stratified in a Swiss glacier, Colle Gnifetti, has established something different.
The study was conducted by the team led by McCormick himself, in collaboration with glaciologist Paul Mayewski at the Climate Change Institute of The University of Maine (UM) in Orono.
The ice cylinder analyzed by scholars tells of storms that carried the sand of the Sahara, of pollution due to human activities, and of ashes rained down from the sky after violent volcanic eruptions.
Two particles of volcanic glass showed a chemical composition similar to Icelandic volcanic rocks: the great cold of 536 would therefore be due to the eruption of a volcano in Iceland (although for some scientists further tests are needed). In any case, whether the devastating eruption occurred in North America or in Iceland, it brought cold, famine and death throughout much of the planet.

In 540 and 547 there were two other eruptions. Meanwhile, in 541, bubonic plague struck the Roman port of Pelusium, in Egypt. What came to be called the Plague of Justinian spread rapidly, wiping out one-third to one-half of the population of the eastern Roman Empire and hastening its collapse, McCormick says.
According to scholars, in Europe it took about a century for the economy to grow again, a figure that is always extrapolated from the same glacier. In 640 there is a spike in airborne lead, that marks a resurgence of silver mining. The disappearance of lead in the Alpine glaciers, between 1349 and 1353, is the sign of another terrible period in human history, that of the Black Plague, but this is another story!

Source: Sciencemag.org. Images from web.