Researchers have used the meteorological observations of ancient Irish monks to correlate Ireland's cold snaps with volcanic activity, Discovery News reported.
The monks wrote down records of the weather in the Irish Annals. They did this over a period of 1,200 years, from 431 to 1649 CE.
The Annals recorded large events and days of religious observance, but also noted weather that was out of the ordinary.
"Exceeding great frost and snow and stormy weather this year, so that no herb grew in the ground and no leaf budded on a tree until the feast of St. Brendan," the Annals of Connacht from 1465 said.
The monks made recordings throughout many disasters, including Viking invasions and the black plague, only stopping when the English took over and changed their culture.
"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 of Harvard University said.
Ludlow's research team studied the writings and tried to find causes of severe weather in the records.
Using the Greenland Ice Sheet Project that studied volcanic residue inside of glaciers, the researchers looked at the correlation between volcanic activity and weather.
The study did find several links, the Peruvian volcano, Huaynaputina, was believed to have caused several years of very severe winter in around 1600. There was also a volcano in China that erupted, resulting in a very cold climate.
"The possibility that tropical eruptions may result in severe winter cooling for Ireland highlights the considerable complexity of the volcano-climate system in terms of the regional expression of the response of climate to volcanic disturbances," Ludlow said.
The team studied 48 volcanoes that erupted over a period from 431 to 1646. A whopping 38 of those volcanoes were able to be associated with extreme climate changes in Ireland.
