A volcanic eruption in Iceland in late 822 was likely responsible for widespread famine, plague, and freezing temperatures throughout Europe, The Economist reports. This is according to new research by a team of scientists lead by Ulf Büntgen, professor of Environmental Systems Analysis at Cambridge.
The 820s were not good years for medieval Europeans, characterized as they were by poor harvests, hailstorms, and temperatures so cold that three rivers that had never frozen—the Danube, the Rhine and the Seine—all iced over. This was about 50 years, give or take two years, before the Norsemen settled Iceland, busy as they were “concentrating their activities on the lootable monasteries and villages of coastal Europe.” As such, unlike with subsequent Katla eruptions—such as the one in 1783 that lasted eight months and is now considered a catalyst for the French Revolution—there’s no firsthand accounts of any Icelandic eruption during this time.
Nevertheless, scientists had long suspected that a major volcanic eruption could have been to blame for the famine and weather conditions of the 820s, as it’s already known that volcanic eruptions can have a dramatic effect on weather when they “eject sulphur dioxide, which reacts with atmospheric gases to form sulphate aerosols that reflect sunlight back into space, cooling the air beneath.” The scientists’ suspicion was also backed up by findings in Greenlandic ice cores, which show “a spike in sulphate levels in layers laid down during those years.”
It was not until Iceland’s ancient Drumbabót forest, which dates back to the 9th century, was uncovered by flooding in 2003 that it seemed like it would finally be possible to pinpoint the exact date and location of the suspected medieval eruption. As explained on the Cambridge University website, “In a similar way to how fossils can be used to understand the development and evolution of life on Earth, different types of environmental evidence can be used to understand what the Earth’s climate was like in the past and why. The ‘fingerprints’ contained in tree rings and ice cores help scientists to estimate past climatic conditions and extend our understanding of the interaction between humans and the environment hundreds and thousands of years back in time.”
Cross-referencing their scientific findings with archival documents from Europe and Asia, Dr. Büntgen and his multidisciplinary team of scientists and historians were thus able to determine that Katla erupted in 822 or 823 AD. “It was a happy coincidence that we were able to use all these different archives and techniques to date this eruption,” said Büntgen. “Data and methods we are using are constantly getting better, and by building more links with the humanities, we can see the real effects volcanoes have on human society.”