It is known that volcanic eruptions have caused climatic changes but quantifying the impacts caused by them has been challenging due to variations in historic atmospheric data observed in ice cores and temperature variations seen in climate proxies such as tree rings.

Researchers in a new study published in Nature resolved these discrepancies with reformation of the timing and associated radiative forcing of nearly 300 individual volcanic eruptions extending from as far back as the early Roman period.

Researchers through their study showed that 15 of the 16 coldest summers ever recorded between 500 BC and 1,000 AD were followed by large volcanic eruptions.

The new reconstruction is derived from over 20 individual ice cores extracted from ice sheets in Greenland and Antarctica. They were further analyzed for volcanic sulfate primarily using DRI’s state-of-the-art, ultra-trace chemical ice-core analytical system.

The ice-core records provided a year-by-year history of atmospheric sulfate levels through time.

Mai Winstrup, Ph.D., a postdoctoral researcher at the University of Washington, Seattle, said, “Previously, this has been done by hand, but we used a statistical algorithm instead. Together with the state-of-the-art ice core chemistry measurements, this resulted in a more accurate dating of the ice cores”.

The study authors noted that identification of new evidence found in both ice cores and corresponding tree rings allowed constraints and verification of their new age scale.

Kees Welten, Ph.D., an associate research chemist from the University of California, Berkeley said in explanation that the discovery of a unique signature in the ice-core records from an extra-terrestrial cosmic ray event, helped to significantly improve the dating accuracy of the ice-core chronologies.