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Reasearch on Pre-Historic Climate Change April 8, 2006

Posted by tkcollier in Enviroment, In The News, Science & Technology.
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AAAS – AAAS News Release
"If you go back in time, you have to go back to the middle Pliocene before you get to see a climate that was as warm as what we are going to see in the next 50 to 100 years in our own time," Chandler said.

Ocean temperatures rose substantially during that warming episode—as much as 7 to 9 degrees Celsius (about 12 to 16 degrees Fahrenheit) in some areas of the North Atlantic. But scientists are puzzled. The carbon dioxide levels at that time — inferred from geochemical data — were roughly comparable to our own time, approaching 400 parts per million.

The natural trigger for the PETM warming episode remains a subject of intense debate, but Thomas said a leading hypothesis involves the release of huge amounts of methane gas that had been trapped in ice compounds called methane hydrates. Methane produces less carbon dioxide than coal when it is burned as a fuel, and it is a powerful greenhouse gas. Most methane hydrates in the present oceans are frozen in sediments in the deep oceans, but some are associated with permafrost soils in the Arctic. Release of the methane can occur through natural processes, including underwater landslides or other seismic events, or by warming of ocean waters. Once released, the gas can induce atmospheric warming that has a positive feedback effect, releasing still more gas as ocean waters and permafrost regions begin to warm. The process can reach a tipping point where it starts to rapidly accelerate.

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