Climate Models Off By 40 Degrees

by William Yeatman on September 3, 2002

in Science

A study in the August 28 issue of Geophysical Research Letters finds that there is a serious error in the global circulation models when it comes to predicting temperatures in the Earths polar regions. The study measured atmospheric temperatures, at the stratopause and mesopause regions (the atmospheric layers at about 30 and 50 miles altitude respectively), at the Earths poles. What the researchers found was that atmospheric temperatures at the South Pole are about 40-50 degrees Fahrenheit cooler than model predictions.

“Our results suggest that wintertime warming due to sinking air masses is not as strong as the models have assumed,” according to Chester Gardner, a professor of electrical and computer engineering and coauthor of the study. “But in all fairness, since no one had made these measurements before, modelers have been forced to estimate the values. And, in this case, their estimates were wrong.”

The researchers made temperature measurements from December 1999 to October 2001 using a laser radar system in combination with weather balloon measurements of the troposphere and lower stratosphere. Temperatures were recorded from the surface to an altitude of 70 miles.

It was discovered that at about 30 miles altitude it was much colder than model predictions, said Gardner. “The greatest difference occurred in July, when the measured stratopause temperature was about 0 degrees Fahrenheit, compared to about 40 degrees Fahrenheit predicted by the models.”

Gardner explains the significance of this finding: “After the autumnal equinox in March, radiative processes begin cooling the polar atmosphere. During the long polar night, the atmosphere above Antarctica receives little sunlight and is sealed off by a vortex of winds that spins counterclockwise. This stable polar vortex prevents the transport of warmer air from lower latitudes into the pole, and leads to extreme cooling of the lower stratosphere.”

The only source of heat during the winter comes from down-welling air masses, which warms the air by compressing it. “Current global circulation models apparently overpredict the amount of down-welling, because they show warmer temperatures than we observed,” said Gardner.

When the researchers plugged their results into the climate model at the National Center for Atmospheric Research in Boulder, Colorado, the difference was significant. “With the reduced down-welling, the predicted mesopause temperature near 60 miles altitude decreased from about minus 120 degrees Fahrenheit to about minus 140 degrees Fahrenheit, in better agreement with our measurements for mid-winter conditions,” Gardner said. “In the stratopause region, the predicted temperature decreased from about 35 degrees Fahrenheit to about 12 degrees Fahrenheit, also in better agreement with our measurements.”


  • The Bush Administrations Climate Action Report 2002 continues to undermine its position on global warming. In a major speech in Mozambique on September 1 just before his appearance at the World Summit, British Prime Minister Tony Blair stated, “They [the Bush Administration] accept the science, but they believe the targets are unachievable without unacceptable economic consequences.”

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