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America's deserts dysfunctionally expand with unchecked Global Warming

by Peggy Chang

Human-caused climate change is likely to lead to long periods of extreme drought throughout the American Southwest starting early this century, finds a new study released 5 April 2007 by the Lamont-Doherty Earth Observatory, a member of The Earth Institute at Columbia University. The is contributing to the expasion of American desert areas.

The researchers compared the coming drought to the Dustbowl of the 1930s that sent millions of environmental refugees fleeing to California from across the Great Plains.

In contrast to past droughts, future drying is not linked to any particular pattern of change in sea surface temperature but seems to be the result of "an overall surface warming driven by rising greenhouse gases," researchers said.

"The arid lands of southwestern North America will imminently become even more arid as a result of human-induced climate change just at the time that population growth is increasing demand for water, most of which is still used by agriculture," said Richard Seager, senior research scientist at the Lamont-Doherty Earth Observatory and one of the lead authors of the study.

Deserts in the Southwestern United States are areas of extreme heat and dryness, just as most of us envision them. More scientifically, deserts, also called arid regions, characteristically receive less than 10 inches of precipitation a year. In some deserts, the amount of evaporation is greater than the amount of rainfall. Semiarid regions average 10 to 20 inches of annual precipitation. Typically, desert moisture occurs in brief intervals and is unpredictable from year to year. About one-third of the earth's land mass is arid to semiarid (either desert or semidesert).

Three of the four major deserts of the United States are contained within a geological region called the Basin and Range Province, lying between the Rocky Mountains to the east and the Sierra Nevadas to the west. While the distinctiveness of each desert is based on the types of plant life found there (determined both by evolutionary history and climates), the geological structures of these three deserts are rather similar.

Projections of climate change caused by human activities conducted by 19 different climate modeling groups around the world, using different climate models, show widespread agreement that southwestern North America, and the subtropics in general, are heading toward a climate even more arid than it is today.

Research documented in the journal Science, shows that there is a broad consensus amongst climate models that this region will dry in the 21st Century and that the transition to a more arid climate may already be underway.

If these models are correct, the levels of aridity of the recent multiyear drought, or the Dustbowl and 1950s droughts, will, "within the coming years to decades, become the new climatology of the American Southwest," the researchers said.

Oil companies are further dwindling the availability of vital drinking water from Global Warming in desert bordering urban areas like Las Vegas and Phoenix, by the releasing of toxic fuel additives into undergound water tables.

"Our study emphasizes the fact that global warming not only causes water shortage through early snow melt, which leads to significant water shortage in the summer over the Southwest, but it also aggregates the problem by reducing precipitation," said Mingfang Ting, one of the study’s co-authors.

"The West, and in particular, the United States and Mexico, need to plan for this right now, coming up with new, well-informed and fair deals for allocation of declining water resources," warned author Seager.

Las Vegas Valley Water District spokesman Scott Huntley says the study reinforces what Colorado River water users like the city of Las Vegas are experiencing right now. "Ground zero is right here in Las Vegas," he said.

"This really is the wake-up call to all of the desert Southwest to cooperate to develop solutions," said Huntley. "We have seen the effects in Lake Powell and in Lake Mead - we've seen that the usage of water along the Colorado has been greater than the flows for seven or eight years now. This has to be the incentive for states and water users to come together."

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