U.S. researchers studied 19 climate computer models and revealed in a study published online Thursday by the journal of Science that changing climate will produce increasing drought in the Southwest, a region where water resources are already dwindling.
"The bottom line message for the average person and also for the states and federal government is that they'd better start planning for a Southwest region in which the water resources are increasingly stretched," said lead author Richard Seager of Columbia University's Lamont Doherty Earth Observatory.
Researchers used data for the computer models dating back to 1860 and projecting into the future. The same models were used in preparing the reports of the Intergovernmental Panel on Climate Change.
The consensus of the models was climate in the southwestern United States and parts of northern Mexico began a transition to drier conditions late in the 20th century and is continuing in this century, as climate change alters the movement of storms and moisture in the atmosphere.
The reduction in rainfall could reach levels of the 1930s Midwest dust bowl, Seager said in a telephone interview.
That doesn't mean there would be dust storms like those of the 1930s, Seager said, because conditions at that time were also complicated by poor agricultural practices.
Currently, the majority of water in the Southwest is used in agriculture, but the urban population of the region is growing and the water needs of people are growing as well, he explained.
"So, in a case where there is a reduced water supply, there will have to be some reallocation between the users," Seager said. "The water available is already fully allocated."
Jonathan T. Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona, said the finding "agrees with what is already happening in the Southwest, and will be further complicated by the already declining spring snowpack due to warming."
"These are scary results, but scary in part because they are results of well thought-out scientific work by a large number of strong scientists," said Overpeck, who was not part of the research team.