For Additional Information:
Dr. John Christy, (205) 922-5763
[email protected]
Phillip Gentry, (205) 890-6414
[email protected]
Climate models produce 'interesting' results
Fourteen of the most popular global climate models, which are used by
scientists to predict global climate change and by policy makers to
formulate appropriate environmental policy, were less prescient than
expected in a major test designed to determine their accuracy in
predicting global warming or cooling.
"It was generally worse than we thought it would be," said Dr. John
Christy, an associate professor of atmospheric science at UAH. "Every
model overestimated the global warming trend by at least four to ten
times what we saw in the actual data."
In a project supported by the U.S. Department of Energy, Christy and
Ph.D. student Justin Hnilo compared the output of 14 major scientific
climate models against global temperature data gathered by microwave
sounding units aboard satellites.
The computerized climate models were run using ten years of sea surface
temperature data collected from ships, buoys and piers around the world.
Sea surface temperatures have long been considered one of the most
important "drivers" of global atmospheric temperatures.
"Ten years is a relatively brief time period in which to judge a model's
ability to produce a trend, so trend variations between models were
expected," Christy said. "It was surprising that every one of the models
showed too much warming."
Christy and Hnilo found that scientists who developed the models give the
oceans too much credit for temperature change in the atmosphere.
"In the models, whenever something happens on the sea surface, the
atmosphere above it immediately responds," Christy explained. "The real
atmosphere isn't that well 'connected' to the oceans. In many regions of
the world the sea surface and the atmosphere are actually decoupled (sea
surface warming results in atmospheric cooling)."
The models also did not accurately represent the efficiency with which
Earth releases heat into space, he said. The cumulative result was models
predicting global warming trends in the mid-troposphere of from 0.13 to
0.35 degrees Celsius per decade. Most of them predicted warming of more
than 0.2 C.
The observed 10-year temperature increase was 0.03 degrees Celsius.
- 30 -
(EDITORS: Dr. John Christy will report on related research at the
American Meteorological Society's convention at the Long Beach Convention
Center in Long Beach, California, on Thursday, Feb. 6, at 2 p.m.)
RSS