Researchers looking at the impact of volcanic activity on the climate over a 1,200 year period have studied ancient Irish texts written by monks who recorded significant events such as descriptions of extreme cold and heat.
These chronicles are generally known as the Irish Annals and in this report, scientists and historians have looked at 40,000 entries in the texts dating from AD431 to 1649.
The researchers also looked at the Greenland Ice Sheet Project (GISP2) ice-core data.
When volcanoes erupt, they produce sulphate aerosol particles which down the centuries have been deposited on and frozen in ice sheets, leaving an extremely accurate temporal record of the event.
Story: Matt McGrath, BBC News | Photo: Francis Ludlow