Swiss study explains what drove cold spells in last 12,000 years

What has driven the cold spells of the last 12,000 years Keystone-SDA

Mystery solved: An international research team has identified the likely cause of abrupt cold spells over the last 12,000 years.

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According to the findings, volcanic eruptions triggered the centuries-long phases of glacier growth, as the Swiss National Science Foundation (SNSF) announced on Thursday.

For their analysis, the team led by Alice Paine from the University of Basel compiled information on 51 major volcanic eruptions during the Holocene, the current geological epoch, which began around 12,000 years ago with the end of the last glacial period, known as the Würm Glacial Period.

The researchers compared the timing of these eruptions with data on glacier extent, which they obtained from the analysis of moraines. They published their findings in the journal Nature Communications.

Energy balance out of equilibrium

The research team found more than 80% of the glacier expansions studied occurred during the same period as at least one volcanic eruption. According to the researchers, the eruptions threw the Earth’s energy balance out of equilibrium.

Sulphur particles ejected into the atmosphere reflected sunlight, which cooled the Earth’s surface. This triggered a chain of self-reinforcing effects, including the expansion of Arctic sea ice and changes in ocean currents.

“All these effects reinforce one another; it works on the snowball principle,” explained researcher Paine in the SNSF press release. This process ultimately led to the growth of the glaciers.

According to the study, it remains unclear whether such a volcanic-induced cooling phase could occur in the future. Paine pointed out that, due to human influence, the climate is in an unprecedented state, which makes forecasts difficult.

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Translated from German, reviewed by an English Department journalist.