Science explains what caused three summerless years in the ninth century
M. Michael Brady
The three summerless years of 821-823 were horrific. Across Europe, blizzards inundated the land; rivers froze; storms raged; famine and plague followed. The pre-Christian Vikings reckoned that Fimbulwinter, the immediate prelude to Ragnarok, the twilight of the Norse gods, had arrived. Christian clerics were of like mind. Paschasius Radbertus (785-865), the Abbot of the Benedictine Monastery in what now is the town of Corbie in the Hauts-de-France region of northern France, wrote that God himself was angered.
But Ragnarok didn’t happen. Carolingian Europe recovered. Obviously no deity had directed the devastation. Scientists now know that volcanic eruptions can affect weather. A sufficiently powerful eruption ejects sulfur dioxide that reacts with gasses in the upper atmosphere to form aerosols that reflect sunlight back into space, cooling the underlying air. So researchers have long suspected that there was a significant eruption in the summerless years of 821-823.
Ice cores collected by the multinational Greenland Ice Core Project (1989 to 1992) strengthened that suspicion, as they showed high atmospheric sulfate levels in the early ninth century. In 2003 a flood in Iceland revealed a forest that apparently had been alive in the ninth century but had been knocked over by an enormous force, probably by a violent flood from the rupture of Myrdalsjokull, the glacier that overlies the Katla volcano some 21 miles away. These clues triggered retrospective scientific detective work by Ulf Büntgen and colleagues at the University of Cambridge together with peers in seven countries. That multinational research effort dated the causal eruption of Katla to 822-823 (Further reading).
The accuracy of the dating shows the power of the scientific method to reveal the history of an event in the absence of extant human-generated records. That said, there may be an alternative history. Dicuil, an early ninth century Irish monk and geographer, wrote about holy men who wandered to the lands of the North. He mentioned Thule, which may have been Greenland or Iceland, but is imprecise, as Celtic hermits also settled other northern islands, including the Orkneys and the Shetlands. In the Íselendingabók (Book of the Icelanders), written between 1122 and 1133, Icelandic chronicler Ari Þorgilsson (1067-1148) mentions the Papar (from the Latin papa), wandering Celtic monks, some of whom took eremitic residence in Iceland before 874, when it was first settled by Norsemen. In any case, had the incoming Norsemen not obliterated whatever records may have been kept by the eremitic Celtic monks, we might have an eyewitness account of the Katla eruption.
Further reading: “Multi-proxy dating of Iceland’s major pre-settlement Katla eruption to 822-823 CE” by Ulf Büntgen et. al, Geology (Geology Society of America journal), June 28, 2017, listing: pubs.geoscienceworld.org/geology/article-abstract/doi/10.1130/G39269.1/208004/multi-proxy-dating-of-iceland-s-major-pre?redirectedFrom=fulltext
This article originally appeared in the Sept. 8, 2017, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.