Prepare for hotter and drier Southwestern US, climate experts urge

Chem.info via Science Daily: Jonathan Overpeck, principal investigator with the Climate Assessment for the Southwest at the UA, and Bradley Udall, director of the Western Water Assessment at the University of Colorado, write in the June 25 issue of the journal Science that such an approach is necessary for coping with a wide range of projected future climate changes in the West and Southwest.

In their overview of shifting climate in the region, Overpeck and Udall cite published findings of prevalent signs of change: rising temperatures, earlier snowmelt, northward-shifting winter storms, increasing precipitation intensity and flooding, record-setting drought, plummeting Colorado River reservoir storage, widespread vegetation mortality and more large wildfires.

"The West, and especially the Southwest, is leading the nation in climate change -- warming, drying, less late-winter snowpack and drought -- as well as the impacts of this change," said Overpeck, a UA professor of geosciences and atmospheric sciences and co-director of the Institute of the Environment.

In the past 10 years, temperatures in almost all areas in western North America have surpassed the 20th century average, many by more than 1 or even 2 degrees Fahrenheit. The warming has decreased late-season snowpack, which serves as a water reservoir, as well as the annual flow of the Colorado River, the researchers said.

Those reductions, combined with the worst drought observed since 1900, haven't helped matters; water storage in Lakes Powell and Mead, the largest southwestern water reservoirs, fell nearly 50 percent between 1999 and 2004 and has not risen significantly since.

In addition to water, vegetation is feeling the effects of climate change. Work by UA's David Breshears and colleagues have already showed that more than 1 million hectares of piñon pine have died in the Southwest in the last few decades from a lethal combination of record-high temperatures and uncommonly severe drought. In addition, the frequency of large wildfires has increased as snowpack has decreased....

Lake Powell, shot by Justin Brockie, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license