Due to climate change, the U.S. Southwest faces a rise in periods of water scarcity that last more than 35 years, a new study reports.
Researchers from Cornell, Columbia and NASA's Goddard Institute based their research on historical climate data such as samples of tree rings, concluding that previous studies underestimated the risk of the punishing periods of extended dryness. The study was published in the journal Scientific Advances.
The statistical risk of such a period of extended dryness was between 5 and 15 percent throughout the 1900s. But in this century, it could soar to as high as 50 percent, if temperatures increase to the upper end of projections.
As around the world, climate change is altering precipitation patterns in the Southwest, increasing in some areas due to more intense storms but reducing it in others, according to a 2014 report by the U.S. Global Change Research Program.
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But if the average annual temperature rises more than 7.2 degrees Fahrenheit in the Southwest over the remainder of the century, it could cause dryness even in areas with more rain, because it will throw off the balance between rain and/or snowfall and evaporation from the soil, the scientists found.
That's a scary prospect for future generations, because NASA says that by 2099, the temperature could rise even higher, to as much as 9.5 degrees F over the present level.
If there's a positive takeaway, it's that the scientists think that megadroughts aren't necessarily inevitable.
"We found that megadrought risk depends strongly on temperature, which is somewhat good news," explained Toby Ault, a Cornell professor of earth and atmospheric science who was the study's lead author. "This means that an aggressive strategy for cutting greenhouse gas emissions could keep regional temperature changes from going beyond about 2 degrees Celsius (3.6 degrees Fahrenheit)."
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Along with Ault, the research team included Justin S. Mankin and Benjamin Cook, both of the NASA Goddard Institute for Space Studies, and Jason E. Smerdon of Columbia University. The National Science Foundation supported the research. Here's a press release with more detail on the study's findings.
Drought can have catastrophic effects, not just on the environment but the economy as well, because dryness can destroy crops and drive up the price of food. A 1988 drought in the Southwest caused an estimated $40 billion economic loss, according to a 2003 study by University of Arizona researchers.
"The Southwest is considered one of the more sensitive regions in the world for increased risk of drought caused by climate change," the Union of Concerned Scientists website notes.
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