If you ask medieval historian Michael McCormick what the worst year to be alive was, he'll tell you: "536." Not 1349, when the Black Death ravaged Europe, wiping out half of the population. Not 1918, when the influenza virus killed 50 to 100 million people, largely teenagers and young adults. 536, on the other hand. According to McCormick, a historian, and archaeologist who chairs the Harvard University Initiative for the Science of the Human Past, "it was the beginning of one of the worst eras to be alive, if not the worst year."
For 18 months, a mystery fog blanketed Europe, the Middle East, and portions of Asia in darkness, day and night. "For the sun, like the moon, put forth its light without brightness throughout the year," stated Byzantine historian Procopius. Temperatures dropped 1.5°C to 2.5°C in the summer of 536, kicking off the coldest decade in the previous 2300 years. Snow came to China that summer, crops failed, and people went hungry. "A lack of bread from the years 536–539," according to the Irish chronicles. Then, in 541, the bubonic plague devastated Pelusium, a Roman port in Egypt. According to McCormick, the Plague of Justinian spread quickly, wiping off one-third to half of the population of the eastern Roman Empire and hastening its demise.
Historians have known for a long time that the middle of the sixth century was a dark period in what was once known as the Dark Ages, but the cause of the enigmatic clouds has remained a mystery. Now, a team led by McCormick and glaciologist Paul Mayewski at the Climate Change Institute of The University of Maine (UM) in Orono has pinpointed a culprit after performing an ultra-precise examination of ice from a Swiss glacier. A devastating volcanic explosion in Iceland sprayed ash throughout the Northern Hemisphere early in 536, according to the experts, who presented their findings at a Harvard symposium this week. In the years 540 and 547, two more large eruptions occurred. As the team explains in Antiquity this week, the repeated blows, followed by a pestilence, pushed Europe into economic stagnation that lasted until 640, when another signal in the ice—a spike in the airborne lead—marks a comeback of silver mining.
The detailed log of natural disasters and human pollution has frozen into the ice, according to Kyle Harper, provost and medieval and Roman historian at The University of Oklahoma in Norman, "gives us a new kind of record for understanding the concatenation of human and natural causes that led to the fall of the Roman Empire—and the earliest stirrings of this new medieval economy."
Researchers have been looking for a reason for the exceptionally chilly summers around the year 540 since tree ring investigations in the 1990s suggested it. Polar ice cores from Greenland and Antarctica revealed a clue three years ago. When a volcano erupts, sulfur, bismuth, and other compounds are released into the atmosphere, where they form an aerosol veil that reflects the sun's light back into space, cooling the earth. A team led by Michael Sigl, now of the University of Bern, discovered that nearly every extremely cold summer over the past 2500 years was preceded by a volcanic eruption by comparing the ice record of these chemical fingerprints with tree ring records of climate.
A huge explosion occurred in late 535 or early 536, possibly in North America, according to the scientists, and another occurred in 540. The twin strike, according to Sigl's research, explains the prolonged darkness and cold.
Mayewski and his multidisciplinary team decided to explore similar eruptions in an ice core drilled in 2013 in the Swiss Alps' Colle Gnifetti Glacier. The 72-meter-long core encases over 2000 years of volcanic ash, Saharan dust storms, and human activity smack in the middle of Europe. The researchers deciphered the record using a novel ultra–high–resolution approach in which a laser carves 120-micron slivers of ice along the length of the core, each reflecting just a few days or weeks of snowfall. About a dozen elements are examined in each of the 50,000 samples taken from each meter of the core. The researchers were able to pinpoint storms, volcanic eruptions, and lead contamination down to the month or even less in the past using this method.
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