Geophys. Res. Lett. 10.1029/2009GL040882 (2009)

Analyses of ice cores from Greenland and Antarctica have revealed a previously unknown tropical volcanic eruption that spewed huge amounts of ash and gas in 1809. The event resulted in a decade, starting in 1810, of the coldest temperatures recorded in the past 500 years.

Jihong Cole-Dai of South Dakota State University in Brookings and his colleagues identified unique isotopic signatures of volcanic sulphate in the core layers from 1810 and 1811 that point towards the eruption. Its exact location remains unknown. The researchers report that the release of sulphur gases, which form Sun-blocking aerosols, by this volcano and the famed 1815 Tambora eruption in Indonesia was sufficient to bring about the cold decade, which included the 'year without a summer' in 1816.