Volcanic eruptions and global climate linked at last

New ice core data has revealed further evidence that volcanic eruptions have a significant and repeated impact on the global climate.

An international research team led by Yale University used deep ice core data taken from ice sheets in Greenland and Antarctica and discovered large volcanic eruptions preceded 15 of the 16 coldest summers recorded between 500 B.C. and A.D. 1,000. The findings resolved inconsistencies in previous studies which failed to demonstrate this relationship.

“Using new records we are able to show that large volcanic eruptions in the tropics and high latitudes were the dominant drivers of climate variability, responsible for numerous and widespread summer cooling extremes over the past 2,500 years,” said research associate Dr Michael Sigl at the Paul Scherrer Institute in Switzerland.

In the study, published in the journal Nature, the team managed to resolve the inconsistencies between historic atmospheric sulphate data from ice cores and corresponding data derived from tree rings and other sources. Previous studies had failed to show a correlation between eruptions and climate change.

Research associate Dr Francis Ludlow, a postdoctoral fellow at the Yale Climate and Energy Institute said: “Previously, there seemed to be a big delay between the dating of eruptions and big dips in tree-ring growth, so that researchers were forced to infer that either the eruptions didn’t actually impact climate, or that there must have been an error in the dating of tree-ring records.”

The team suggest that the cooler temperatures were caused by large amounts of volcanic sulphate particles in the upper atmosphere, shielding the Earth’s surface from incoming solar radiation. They believe that volcanic eruptions have triggered one of the most dramatic climatic changes in recent human history – the unusually cold summers from A.D. 536-550 in the Northern Hemisphere.

Dr Ludlow added: “Before the new chronology, there were no eruptions that could have convincingly caused such a prolonged period of climatic and social disturbance but with the new dating we can now identify a major eruption in the high latitudes of the Northern Hemisphere in 536, followed by another huge eruption in the tropics around 540. It was this double-whammy that led to such severe and prolonged impacts.”

Paper: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14565.html