Global Warming Less Severe in Central U.S.

Iowa State University modeling shows that warming in the United States will be stronger in winter than summer and stronger at night than during the day.

Scientists at the Regional Climate Modeling Laboratory at Iowa State University have discovered global warming might not be as severe in the central United States as in other parts of the country. Using a detailed regional climate model, they estimate summertime daily maximum temperatures will warm less in a region centered on eastern Kansas than anywhere else in the United States.

The findings, in the current issue of Geophysical Research Letters, underscore the need to consider the impact of global warming on a region-by-region basis, says Gene Takle, professor of agronomy and geological and atmospheric sciences. "Modeling allows us to make projections of future scenario climates," he says.

"The modeling showed that warming in the United States will be stronger in winter than summer and stronger at night than during the day. But we found what looked to us like a 'hole' in the daytime warming in summer, which was a surprise," lead author of the article Zaitao Pan says.

After discovering the 'hole' in climate projections for the 2040s, Pan went back to carefully examine the observed maximum daily temperatures from 1975-2000 in a region that centers in eastern Kansas and touches parts of Missouri, Oklahoma, Nebraska and Iowa. "We found that, in fact, this hole already has started to develop," he says.

Ray Arritt, Iowa State agronomy professor, says the existence of this 'hole' in the warming, makes sense. "Our model tells us the future climate will have more rainfall and wetter soil, so more of the sun's energy goes into evaporating water than heating the air," he says. "Rainfall in the northern Great Plains already has increased by about 10% over the past few decades, which is consistent with our predictions."

Team members caution that independent evaluations are needed to confirm this finding and to determine whether the 'hole' might be a temporary phenomenon that will disappear as global warming becomes more severe in the latter half of the 21st century.

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