Journal Highlights

Did the Laki volcano eruption cause the cold winter of 1783-1784?

In June 1783 the Laki volcano in Iceland began to erupt, and continued erupting for months, causing a major environmental disaster. The eruption spewed out toxic sulfuric acid aerosols, which spread over northern latitudes and caused thousands of deaths. That summer, there were heat waves, widespread famines, crop failures, and livestock losses. During the following winter, temperatures in Europe were about 2°C below average for the late 1700s; the winter was also one of the most severe of the past 500 years in eastern North America. The Laki eruption has been blamed for the anomalously cold winter of 1783–1784. However, a new study by D'Arrigo et al. (2011) challenges that interpretation, suggesting instead that the cold winter was caused not by the Laki eruption but by an unusual combination of a negative phase of the North Atlantic Oscillation (NAO) and an El Niño-Southern Oscillation (ENSO) warm phase. The authors analyzed 600-year tree ring reconstructions to show that the NAO and ENSO indices were similar to their values during the 2009–2010 winter, which, like the 1783–1784 winter, was unusually cold and snowy across western Europe and eastern North America. The 2009–2010 winter has been shown to be attributable to NAO and ENSO conditions (and their combined effect), not to greenhouse gas forcing or other causes. The authors add that other data and climate simulations support their hypothesis that this natural NAO/ENSO variability, not the Laki eruption, caused the cold winter of 1783–1784.

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