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Computer models predict extreme weather ahead

The U.S. West is among the regions expected to be most affected by global warming.

By ASSOCIATED PRESS
Published October 23, 2006

WASHINGTON - The world - especially the Western United States, the Mediterranean region and Brazil - will likely suffer more extended droughts, heavy rainfalls and longer heat waves over the next century because of global warming, a new study forecasts.

But the prediction of a future of nasty extreme weather also includes fewer freezes and a longer growing season.

In a preview of a major international multiyear report on climate change that comes out next year, a study out of the National Center for Atmospheric Research details what nine of the world's top computer models predict for the lurching of climate at its most extreme.

"It's going to be a wild ride, especially for specific regions," said study lead author Claudia Tebaldi, a scientist at the federally funded academic research center.

Tebaldi pointed to the Western United States, Mediterranean nations and Brazil as "hot spots" that will get extremes at their worst, according to the models.

And some places, such as the Pacific Northwest, are predicted to get a strange double whammy of longer dry spells punctuated by heavier rainfall.

As the world warms, more rain is likely in the tropical Pacific Ocean, and that will change the air flow for certain areas, much like El Nino weather oscillations now do, said study co-author Gerald Meehl, a top computer modeler at the research center. Those changes will affect the U.S. West, Australia and Brazil, even though it's on South America's eastern coast.

For the Mediterranean, the issue has more to do with rainfall in the tropical Atlantic Ocean changing air currents, he said.

"Extreme events are the kinds of things that have the biggest impacts, not only on humans, but on mammals and ecosystems," Meehl said. The study, to be published in the December issue of the peer-reviewed journal Climatic Change, "gives us stronger and more compelling evidence that these changes in extremes are more likely."

The researchers took 10 international agreed-upon indices that measure climate extremes - five that deal with temperature and five with precipitation - and ran computer models for the world through the year 2099.

What Tebaldi called the scariest results had to do with heat waves and warm nights. Everything about heat waves - their intensity, length and occurrence - worsens. And every part of the globe is predicted to experience a tremendous increase in the number of nights during which the low temperature is extremely high.

Tebaldi's assessment jibes with the National Climatic Data Center's tracking of extreme events in the United States, said David Easterling, chief of the center's scientific services. His group has created a climate extreme index that measures the weather in America. Last year, the United States experienced the second-most-extreme year in 95 years; the worst year was in 1998.

[Last modified October 23, 2006, 01:56:54]