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Global Warming Begets More Warming: MIT Paleoclimate Researchers Discover a “Warming Bias” – SciTechDaily

Global Warming Begets More, Extreme Warming

Global warming begets more, extreme warming, a new MIT paleoclimate study finds. Credit: MIT News

Researchers observe a “warming bias” over the past 66 million years that may return if ice sheets disappear.

It is increasingly clear that the prolonged drought conditions, record-breaking heat, sustained wildfires, and frequent, more extreme storms experienced in recent years are a direct result of rising global temperatures brought on by humans’ addition of carbon dioxide to the atmosphere. And a new

The researchers say a possible explanation for this warming bias may lie in a “multiplier effect,” whereby a modest degree of warming — for instance from volcanoes releasing carbon dioxide into the atmosphere — naturally speeds up certain biological and chemical processes that enhance these fluctuations, leading, on average, to still more warming.

Interestingly, the team observed that this warming bias disappeared about 5 million years ago, around the time when ice sheets started forming in the Northern Hemisphere. It’s unclear what effect the ice has had on the Earth’s response to climate shifts. But as today’s Arctic ice recedes, the new study suggests that a multiplier effect may kick back in, and the result may be a further amplification of human-induced global warming.

“The Northern Hemisphere’s ice sheets are shrinking, and could potentially disappear as a long-term consequence of human actions” says the study’s lead author Constantin Arnscheidt, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “Our research suggests that this may make the Earth’s climate fundamentally more susceptible to extreme, long-term global warming events such as those seen in the geologic past.”

Arnscheidt’s study co-author is Daniel Rothman, professor of geophysics at MIT, and  co-founder and co-director of MIT’s Lorenz Center.

A volatile push

For their analysis, the team consulted large databases of sediments containing deep-sea benthic foraminifera — single-celled organisms that have been around for hundreds of millions of years and whose hard shells are preserved in sediments. The composition of these shells is affected by the ocean temperatures as organisms are growing; the shells are therefore considered a reliable proxy for the Earth’s ancient temperatures.

For decades, scientists have analyzed the composition of these shells, collected from all over the world and dated to various time periods, to track how the Earth’s temperature has fluctuated over millions of years. 

“When using these data to study extreme climate events, most studies have focused on individual large spikes in temperature, typically of a few degrees DOI: 10.1126/sciadv.abg6864

This research was supported, in part, by MIT’s School of Science.

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