Why the Southwest could become drier

The Arizona Republic's Waterblogged blog summarized a raft of recent scientific studies about water temperature increases in rivers and the potential impact on our water supplies.    Two studies examined speleothems in Arizona and New Mexico as analogues for modern changes. [right, Colorado River basin.  Credit, Colo. River Commission of NV]

"we use an oxygen isotope record from a speleothem collected from the Cave of the Bells, Arizona, USA, to reconstruct aridity in the southwestern United States during the last glacial period and deglaciation. We find that, during this period, aridity in the southwestern United States and climate in the North Atlantic region show similar patterns of variability.   A similar response to future warming would exacerbate aridity in this already very dry region."

Moisture variability in the southwestern United States linked to abrupt glacial climate change,
J. D. M. Wagner, J. E. Cole, J. W. Beck, P. J. Patchett, G. M. Henderson & H. R. Barnett

Nature Geoscience 3, 110 - 113 (2010), Published online: 10 January 2010 | doi:10.1038/ngeo707,

http://www.nature.com/ngeo/journal/v3/n2/full/ngeo707.html

"Our data are consistent with modern evidence for a northward shift of the polar jet stream in response to global warming, which could lead to increasingly arid conditions in southwestern North America in the future."

 Variable winter moisture in the southwestern United States linked to rapid glacial climate shifts,  Yemane Asmerom, Victor J. Polyak & Stephen J. Burns,  Nature Geoscience 3, 114 - 117 (2010), Published online: 24     January 2010 | doi:10.1038/ngeo754,  http://www.nature.com/ngeo/journal/v3/n2/full/ngeo754.html