Irish Monks Unknowingly Recorded Centuries of Volcano History

The chronicles of medieval Irish monks preserved in writing a period of ancient history that might have been otherwise lost, but a recent analysis of entries written in the Irish Annals found a link between historic volcanic eruptions and climate change on in Ireland.

At monasteries across medieval Ireland, monks recorded significant events such as feast days, obituaries and instances of extreme weather, the chronicles are generally known as the Irish Annals. Researchers at the Harvard University Center for the Environment and Department of History scrutinized 40,000 entries in the Irish Annals dating between the 1,218-year period between 431 to 1649.

In the same twelve-century time span, a record of volcanic eruptions has been documented in what's known as the Greenland Ice Sheet Project (GISP2), which measures the levels of volcanic sulfate in annual layers of ice.

Comparing the monks' records with the volcanic history preserved in the ice, the researchers found that of 38 volcanic events in the time frame, 37 were associated with the monks' direct observations of extreme cold weather.

"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," Francis Ludlow, lead study author, said in a news release.

Ludlow told the BBC that Irish scribes were consistent in their documentation of extreme weather, which was a boon to the study. He also noted how his team was able to use the ancient records in a way that the ancient scribes would have never concieved.

The time period analyzed produced a total record of 48 volcanic eruptions, 37 of which were consistent with the monks' record of extreme cold temperatures.

"Our major result is that explosive volcanic eruptions are strongly, and persistently, implicated in the occurrence of cold weather events over this long timescale in Ireland. In their severity, these events are quite rare for the country's mild maritime climate," Ludlow said.

The research is published in the journal Environmental Research Letters.