Global Warming & the Feedback Effect

Reported August 2010

COLLEGE STATION, TX (Ivanhoe News) -- With temperatures soaring this summer, global warming is on many people's minds. This June was the hottest on record, according to the National Oceanic and Atmospheric Administration (NOAA). But while most know about the increased levels of carbon dioxide in the atmosphere, have you heard about what it does to the humidity?

Exhaust from your car, smoke from power plants, even volcanic eruptions. That's how global warming heats the earth, right? So here's a fact, all the carbon dioxide emitted from cars doesn't measure up to the damage caused by water.

Texas A&M atmospheric scientist Andrew Dessler, Ph.D., an atmospheric scientist at Texas A & M University in College Station, calls it the “feedback effect.”

"Water vapor doubles the amount of warming you get from carbon dioxide alone," Dr. Dessler told Ivanhoe.

Here's the gist: more C02 in the atmosphere increases the temperature. This causes more water on the earth to evaporate into the air increasing the humidity. Since water vapor is also a greenhouse gas, this makes the atmosphere temperature even hotter.

"The question is not, 'Is the earth going to warm or not?' It's a question of, 'Is it going to warm two degrees, or three degrees, or four degrees,'" Dr. Dessler explained.

Dr. Dessler says this nasty combo will boost the earth's temperature between four and eight degrees Fahrenheit over the next century. And if that seems like no big deal, consider this; the current global temperature is 59 degrees. It was just 10 degrees colder during the last ice age.

"Once you have the initial warming, you really can't stop the amplification,” Dr. Dessler said.

Dr. Dessler urges widespread energy conservation. He says it's best to pretend the current temperature fits like your favorite outfit.

"If you got taller or you got shorter, you're clothes aren't going to fit any better. Your clothes are maximally designed to fit you now," Dr. Dessler explained.

And this outfit is the only one we've got.

Dr. Dessler says the "cloud feedback" is also an up and coming, but poorly understood atmospheric problem. Clouds reflect sunlight back to space, cooling our planet, but there are suggestions that, as the planet warms, fewer clouds will let more sunlight through to the surface.

The American Geophysical Union and the American Meteorological Society contributed to the information contained in the TV portion of this report.

Click here to Go Inside This Science or contact:

Andrew Dessler
Atmospheric Sciences
Texas A&M
(979) 862-1427
adessler@tamu.edu

Peter Weiss
American Geophysical Union
Washington, DC 20009-1277
(202) 777-7507
http://www.agu.org
pweiss@agu.org

American Meteorological Society
Boston, MA 02108-3693
(617) 227-2425
http://www.ametsoc.org

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