Climate Change: Volcanic Eruptions Changed Human History

It's well known that large volcanic eruptions can impact the climate. Now, scientists have found that volcanic eruptions may be responsible for cooling the Earth during the early Roman period.

"Using new records we are able to show that large volcanic eruptions in the tropics and high latitudes were the dominant drivers of climate variability, responsible for numerous and widespread summer cooling extremes over the past 2,500 years," said Michael Sigl, one of the researchers, in a news release. "These cooler temperatures were caused by large amounts of volcanic sulfate particles injected into the upper atmosphere, shielding the Earth's surface from incoming solar radiation."

The researchers found that 15 of the 16 coldest summers recorded between 500 BC and 1,000 AD followed large volcanic eruptions. In addition, four of the coldest occurred shortly after the large volcanic events found on record.

"We used a new method for producing a timescale," said Mai Winstrup, one of the researchers. "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 findings reveal a bit more about how sustained volcanic cooling events impacted climate. In the past, these events triggered crop failures and famines. They may have also contributed to pandemics and societal decline in agriculture-based communities.

"As a result, climate variability observed during more recent times can be put into a multi-millennial perspective-including time periods such as the Roman Warm Period and the times of significant cultural change such as the Great Migration Period of the 6^th century in Europe," said Joe McConnell, one of the researchers.

The findings are published in the journal Nature.

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