Saturday, July 25, 2009

Waning Pacific Clouds Suggest Global Warming Feeds Upon Itself

This will probably not come as a surprise to climate scientists, since past models of the effects of the increasing CO2 we are producing have mostly underestimated how much warming actually occured. There are various feedback mechanisms such as this, and almost all of the ones that have been occurred have been positive feedback loops such as this.

By Jeremy van Loon
July 24 (Bloomberg) -- Fewer clouds dot the Pacific skies than a half-century ago, allowing the sun beat to down on the sea and raise temperatures, according to scientists who say the discovery means our planet may heat up more than forecast.

A self-perpetuating cycle, triggered by global warming, has appeared in weather data gathered from 1952 to 2007 over a 3 million-square-kilometer (740,000 square-mile) expanse of ocean off Mexico, Amy Clement of the University of Miami and colleagues wrote in this week’s edition of Science.

Clouds, like forest fires and Arctic permafrost, are studied for their potential to amplify warming. There is still enough mystery in how they function that scientists have said it’s difficult to produce a consensus forecast for temperatures, which in turn may determine the severity of future storms, droughts and Arctic ice melting.

“There’s a wide range of predicted warming for the 21st century,” Clement, a professor of meteorology and oceanography, said in a podcast on the Science Web site. “This study indicates that perhaps we should be giving serious consideration to the high range of future warming.”

Trying to stem climate change, a 17-member group of the Earth’s most polluting nations including the U.S. and China agreed this month to limit the global average temperature increase to no more than 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial times. They couldn´t agree on targets for reducing greenhouse-gas emissions, leaving that for climate treaty talks that are set to conclude in December.

The average global temperature already has risen by about 0.8 degrees, and more than double that in the Arctic.

The researchers studied 18 models used by the United Nations’ Intergovernmental Panel on Climate Change, the Geneva- based clearinghouse for scientific studies were studied. The found only one model, developed by the U.K. Met Office, accurately predicted changes observed in low-level clouds.

The U.K. model projects a 4.4-degree Celsius warming in a scenario where the concentration of carbon dioxide in the atmosphere doubles. That forecast was the highest increase among the various models, Clement said.

The latest IPCC report estimated a range of 2 degrees to 4.5 degrees with a doubling of CO2.

Carbon dioxide in the atmosphere amounts to about 385 parts per million molecules of air, up from about 280 parts per million at the beginning of the industrial age.

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