The mystery of bitter Irish winters solved

Scientists have found an explanation for the periods of extreme cold described in the writings of Irish monks: volcanic eruptions, some very far away.

About 1,582 years ago, some Irish scribes sat down to write about how very, very cold it was. This was the Dark Ages, after all.

In 2013, scientists also sat down to read those same 40,000 tales of woe — now collected in the Irish Annals, written from 431 to 1649 — and compared them with measurements taken from ice cores dating from the same 1,200-year period. What they found was an explanation for the punishing Irish winters through which the poor scribes shivered: volcanic eruptions, often thousands of miles away.

Their results, published in Environmental Research Letters, showed that out of 48 explosive volcanic eruptions identified in the Greenland Ice Sheet Project (GISP2) ice-core – which records deposits of volcanic sulfate in annual layers of ice – 38 were associated with 37 extreme cold events in Ireland described in the scribes’ writings and identified using modern Irish meteorological data. 

At times, the ancient Irish had events far from their homeland to blame for the bad weather. In one instance, the 1600 eruption Huaynaputina, in Peru, resulted in extreme cold winter weather to Ireland for several years following.

Volcanic eruptions have long been understood to dramatically alter the earth’s climate, though their role in governing ancient weather is new territory for scientists. When a volcano erupts, it shoots sulfur dioxide gas into the atmosphere. The gas is converted into sulphate aerosol particles that reflect incoming sunlight, temporarily cooling the Earth's surface.

"With a few honourable exceptions, the Irish record of extreme events has only been used anecdotally, rather than systematically surveyed and exploited for the study of the climate history of Ireland and the North Atlantic, and so the richness of the record has been largely unrecognized," said Dr Francis Ludlow, from the Harvard University Center for the Environment and Department of History and the lead author of the study, in a press release.

“It's clear that the scribes of the Irish Annals were diligent reporters of severe cold weather, most probably because of the negative impacts this had on society and the biosphere,” he said, in a press release.

 No word yet on when we'll see a line of "Ancient Irish Scribe" branded gloves.