February 25, 2009

Study: Humidity expands global warming

A U.S.-Australian study has determined high humidity levels, through a process called water vapor feedback, can aggravate global warming.

Texas A&M University Professor Andrew Dessler says warming due to increases in greenhouse gases will lead to higher humidity in the atmosphere. And because water vapor itself is a greenhouse gas, this will cause additional warming.

It's a vicious cycle, said Dessler. Warmer temperatures mean higher humidity, which in turn leads to even more warming. For years, there was a debate over this mechanism, with some even questioning if the water vapor feedback existed at all. But recent work on this feedback has moved its existence and strength beyond argument.

He said estimates of significant global warming suggest the Earth will warm from 2 to 4 degrees Celsius (4 to 8 degrees Fahrenheit) during the next 100 years -- a scenario that could have devastating long-term consequences.

Everything shows that the climate models are probably getting the water vapor feedback right, which means that unless we reduce emissions, it is going to get much, much warmer on our planet by the end of the century, he said.

The research by Dessler and co-author Steven Sherwood of the Climate Change Research Center at the University of New South Wales appears in the Feb. 20 issue of Science magazine.