Volcanic origin for Little Ice Age


Glaciers in the Alps have receded dramatically from their most historically recent maxima (the Little Ice Age, AD 1750-1850). This painting by Birman in 1826 illustrates the Mer de Glace, France soon after the glacier had reached its maximum extent (Gugelmann Collection, Swiss National Library, Bern).

Richard Black, Environment correspondent for BBC News, reports: “The Little Ice Age was caused by the cooling effect of massive volcanic eruptions, and sustained by changes in Arctic ice cover, scientists conclude.

An international research team studied ancient plants from Iceland and Canada, and sediments carried by glaciers.

They say a series of eruptions just before 1300 lowered Arctic temperatures enough for ice sheets to expand.

Writing in Geophysical Research Letters, they say this would have kept the Earth cool for centuries.

The exact definition of the Little Ice Age is disputed. While many studies suggest temperatures fell globally in the 1500s, others suggest the Arctic and sub-Arctic began cooling several centuries previously.

The global dip in temperatures was less than 1C, but parts of Europe cooled more, particularly in winter, with the River Thames in London iced thickly enough to be traversable on foot.

What caused it has been uncertain. The new study, led by Gifford Miller at the University of Colorado at Boulder, US, links back to a series of four explosive volcanic eruptions between about 1250 and 1300 in the tropics, which would have blasted huge clouds of sulphate particles into the upper atmosphere.

These tiny aerosol particles are known to cool the globe by reflecting solar energy back into space.”

Read on at the BBC.

Follow author Richard Black on Twitter.

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