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Bursts of intense global warming that have lasted tens of thousands of years have taken place more frequently throughout history than previously believed, according to evidence gathered by a team led by Scripps Institution of Oceanography, UC San Diego researchers.

Richard Norris, a professor of geology at Scripps who co-authored the report, said that releases of carbon dioxide sequestered in the deep oceans were the most likely trigger of these ancient “hyperthermal” events. Most of the events raised average global temperatures between 2° and 3° Celsius (3.6 and 5.4° F), an amount comparable to current conservative estimates of how much temperatures are expected to rise in coming decades as a consequence of anthropogenic global warming. Most hyperthermals lasted about 40,000 years before temperatures returned to normal.

Sediment samples in the lab of Richard Norris obtained by the Ocean Drilling Program reveal the mark of “hyperthermals,” warming events lasting thousands of years that changed the composition of the sediment and its color.

The study appears in the March 17 issue of the journal Nature.

“These hyperthermals seem not to have been rare events,” Norris said, “hence there are lots of ancient examples of global warming on a scale broadly like the expected future warming. We can use these events to examine the impact of global change on marine ecosystems, climate and ocean circulation.”

Further details here.