UAH study reinforces Lindzen's "Iris effect"

Submitted by admin on Fri, 2007-09-14 00:29.

A recent University of Alabama-Huntsville study -- with results published in the Aug. 9, 2007 edition of American Geophysical Union's Geophysical Letters -- appears to confirm (or at least support) the theory that when the Earth's atmosphere warms, cirrus clouds -- the high, thin wispy clouds in the upper atmosphere -- dissipate and allow the heat to escape into space. As the heat leaves the atmosphere and the surface cools, the clouds reform and begin to trap heat again.

The UAH study is described in a September 4, FoxNews.com article.

But the new research from the University of Alabama-Huntsville supports the validity of the iris effect.

Analyzing six years of data from four instruments aboard three NASA and NOAA satellites, the UAH researchers tracked precipitation amounts, air and sea surface temperatures, high- and low-altitude cloud cover, reflected sunlight and infrared energy escaping out to space.

Rather than the hypothesized positive feedback of the climate models, the UAH data actually shows a strong negative feedback. As the tropical atmosphere warms, cirrus clouds decrease, allowing infrared heat to escape from the atmosphere to outer space.

"To give an idea of how strong this enhanced cooling mechanism is, if it was operating on global warming, it would reduce [climate model-based] estimates of future warming by 75 percent," said UAH researcher Roy Spencer in a media release.

"The role of clouds in global warming is widely agreed to be pretty uncertain," Spencer said. "Right now, all climate models predict that clouds will amplify warming. I'm betting that if the climate models' 'clouds' were made to behave the way we see these clouds behave in nature, it would substantially reduce the amount of climate change the models predict for the coming decades."

Despite claims of a broad scientific consensus on the causes and potential impacts of global climate change, research such as this appears to be raising more questions and bringing about less certainty. As the article notes in the closing paragraph, the iris effect will require more research before it can be completely confirmed.