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How Earth Survived Past Global Warming
February 10, 2004
Scientists in the U.K. have figured out how the Earth recovered from a sudden episode of global warming during the time of the dinosaurs. This could help us understand how to survive the upcoming climate change.

Global warming caused the erosion of rocks to increase by 400%, leaching calcium and magnesium into the ocean. This erosion could have been caused by an increase in rainfall, as well as higher ocean levels. These chemicals combined with the carbon dioxide that had been absorbed by the ocean, causing a chemical reaction that led to falling levels of greenhouse gases worldwide. Over a period of about 150,000 years, the Earth returned to normal.

Calcium combining with CO2 would have created calcium carbonate, which does not increase global warming. Researcher Anthony Cohen says, "This intense rock- weathering effectively put a brake on global warming through chemical reactions that consumed the atmosphere's extra carbon dioxide."

But how did the world heat up in the first place? (Since dinosaurs didn't drive SUVs). About 180 million years ago, temperatures on Earth rapidly shot up, probably due to the sudden release of huge amounts of methane from the ocean floor. Methane is a greenhouse gas which quickly changes to CO2, which stays in the atmosphere for a long period of time, absorbing sunlight and heating up the Earth.

But where did the methane come from? Besides the vast amounts that are frozen deep in the ocean floor, it may have also come from the vast peat bogs in 200,000 miles of Siberia. Climatologist Laurence Smith says, "The bottom line is Siberian peat lands may be a bigger player in climate change than we knew before."

And what triggers the methane release? Scientists at the University of Wyoming say the ocean methane is released when water temperatures rise. The methane in the ocean is in a highly pressurized form and heat causes faults in the ocean floor where it's stored to break apart, releasing the gas. Matthew Horbach says, "It's like a cork in a champagne bottle. If you shake up the champagne and build up enough pressure, the champagne bubbles can pop the cork."

Smith says, "[This research] emphasizes a point that has been emerging over the past few years; the idea that the climate system is highly unpredictable and full of thresholds that can trigger greenhouse gas sources and sinks to abruptly switch on and off. The more of them we can identify, the more accurately we can model and anticipate changes in the future."

Cohen says, "What we have learned from these rocks is how the Earth can, over a long time, combat global warming. What we need to discover now is why and at what point it goes into combat mode, and precisely how long the conflict takes to resolve."