As the country sizzles from Phoenix to Las Vegas, scientists and environmentalists are saying, "I told you so."
Although it's hard to judge long-term trends from individual seasons, a study co-written by researchers at Columbia and Princeton universities confirms that long-term drought is already under way in the American Southwest — one that may last the rest of this century, if not longer.
These scientists attribute this new climatology in one of the fastest-growing regions of the United States to global warming.
"It's already on the way," said senior researcher and geophysicist Richard Seager of the Lamont-Doherty Earth Institute at Columbia University. "Even if we intervene, it will persist for a few more decades. It takes that long to respond."
Seager and his colleagues at Lamont-Doherty, and at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Lab at Princeton, looked at 19 different computerized climate models from around the world.
Similar to those used for weather forecasting, the models dated back to 1860 and projected to 2100. The models showed a marked increase in arid climate beginning around now and worsening through the current century.
The team reported its findings this year at the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, often called the supreme court of climate science. Its research was also published in April in the journal Science.
Today, temperatures climbed to 115 degrees in parts of Arizona and as high as 125 degrees in Baker, Calif. Power plants failed in the now week-old heat wave.
Meteorologists report that summer temperatures are running 10 to 15 degrees above normal in states like Utah and Nevada.
"It's dangerously hot," said Rob Smith, whose thermometer reached 104 degrees in the shade this morning at his Sonora Desert home in Arizona. "This is what global warming looks like."
As regional staff director of the Sierra Club, Smith has watched trees die of insect infestations and reservoirs for power and drinking water dwindle. For the second year in a row, fireworks were cancelled in Flagstaff near the Grand Canyon because of threat of fire.
The study predicts that the drought could be as severe as the Dust Bowl of the 1930s. Unlike historical droughts, this climate change seems linked to the overall warming of the oceans and atmosphere caused by rising greenhouse gases, according to the Columbia study.
The Colorado River is the "lifeblood" of the Southwest and supplies most of the water to the region. Its levels have dropped by about 15 percent. About 90 percent of its water is used for agriculture, but as the population swells, so will the need for drinking water.
Five of the 10 fastest-growing states are in the Southwest, and nearly 1 million newcomers moved to Arizona, Nevada, Texas, Utah and Texas last year, according to 2006 census data.
"It is certainly consistent with what scientists have projected," said Dan Becker, director of the global warming program at the Sierra Club. "We're certainly seeing worse drought in the Southwest as a harbinger of things to come."
The searing heat of the Southwest means people largely stay indoors and jack up their air conditioners. When they do go out, they drive everywhere, according to Becker.