CO2: Missing Link to Past Climate Changes

Flaming Iced Earth

A Brown University research team established that over the last 2.7 million years, climate in the tropics have changed and concluded that carbon dioxide is a key role in determining global climate patterns.

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"We think we have the simplest explanation for the link between the Ice Ages and the tropics over that time and the apparent role of carbon dioxide in the intensification of Ice Ages and corresponding changes in the tropics," said Timothy Herbert, professor of geological sciences at Brown and the lead author of the paper in Science.

"It certainly supports the idea of global sensitivity of climate to carbon dioxide as the first order of control on global temperature patterns," Herbert added, "but we don't know why. The answer lies in the ocean, we're pretty sure."

The research team then began looking at chemical remains of marine organisms that lived in sun-exposed zones in the ocean. They were able to extract surface temperatures of the oceans for the last 3.5 million years and discovered that ocean temperatures drop by 2 to 5 degrees Fahrenheit during each Ice Age.  The tropics also change when Ice Age cycles switched from intervals of 41,000 to 100,000 years.

"The tropics are reproducing this pattern both in the cooling that accompanies the glaciation in the Northern Hemisphere and the timing of those changes," Herbert said. "The biggest surprise to us was how similar the patterns looked all across the tropics since about 2.7 million years ago. We didn't expect such similarity."

Climate scientists have a record of carbon dioxide levels for the last 800,000 years, spanning the last seven Ice Ages. Carbon dioxide levels in the atmosphere fell by about 30 percent during each cycle, and that most of that carbon dioxide was absorbed by high-latitude oceans such as the North Atlantic and the Southern Ocean. New findings say that the pattern began 2.7 million years ago, and the amount of atmospheric carbon dioxide absorbed by the oceans intensifies with each successive Ice Age.

"It seems likely that changes in carbon dioxide were the most important reason why tropical temperatures changed, along with the water vapor feedback," Herbert said.

Questions that are now being asked are, why carbon dioxide began to play a major role when the Ice Ages began 2.7 million years ago?  And why carbon dioxide appears to have magnified the intensity of successive Ice Ages from the beginning of the cycles to the present? Some just argue that CO2 plays little or no role.

References:
http://www.sciencentechnologyupdates.com/2010/06/co2-missing-link-to-past-climate.html#.TpJb195fbQo

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