MORE THAN 1,500 years ago, Irish monks began to keep a record of life at the time, writing about the weather, politics and major monastic happenings.

Now, researchers have used the diaries to find out how major world weather events at the time – such as volcanic eruptions – were felt in Ireland.

The study used a novel approach: typically when geographers try to examine the impact of volcanoes, they focus only on eruptions during recent decades when meterological instrumental records were available. The new study, however, by researchers from Ireland and three other countries, used the Irish Annals dating between 431 and 1649 AD to examine whether any fallout from the volcanic activity was documented.

The study found that of 48 major volcanic eruptions over the period of 1,200 years, 38 were noted in the Irish Annals, typically in the form of severely cold weather.

The Irish Annals are one of the main primary sources about Ireland during the middle ages. They are made up of more than one million words and around 40,000 different entries describing major historical events every year.

“It’s clear that the scribes of the Irish Annals were diligent reports of severe cold weather, most probably because of the negative impacts this had on society and the biosphere,” said Dr Francis Ludlow of Harvard University, the lead author of the study and a former TCD lecturer.

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.

The injection of sulphur dioxide gas into the stratosphere after a volcano erupts can have a big role in how the Earth’s climate responds. Monks noted heavy snowfall and frost, ice covering lakes and rivers for long periods of time and other severely cold weather patterns in the months after volcanic eruptions in other countries.

The research is published in the journal Environmental Research Letters.

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