Thursday, March 15, 2007
More Drought News
John Fleck at Inkstain reports today on some drought news from around the world, including camels mad with thirst in Austalia. Well, no mad cows to report here in Colorado, but on the University of Colorado campus, abnormal warmth has ushered in flip flop season. So I thought it would be interesting to describe the details of a developing drought in the West that has some people worried.
Sixty percent of the region is now abnormally dry — or worse — according to the U.S. Drought Monitor. About 27 percent of the West is either in severe or exceptional drought, including nearly the entire state of Wyoming. The National Resources Conservation Service predicts that streamflows in a large swath of the West will be significantly below normal in spring and summer. Some flows are expected to be less than 50 percent of normal.
In the Upper Colorado River Basin, drought conditions from 2000 through 2004 had reduced the water level in Lake Powell so much that storage in the reservoir reached a low of 33 percent of capacity. Wetter conditions in 2005 improved the situation a bit, but drier conditions returned to the upper basin in 2006 — and things aren't looking any better now, according to the U.S. Bureau of Reclamation. Precipitation in the basin was below average from November through January, and inflows into the lake from April through July are forecast to be just 71 percent of average.
That situation could turn around If spring precipitation turns out to be much above average. But that seems unlikely, now that the fall's moderate El Niño has rapidly dissapated, and conditions are becoming favorable for a La Niña to develop. (See the El Niño/Southern Oscillation Diagnostic Discussion issued by the National Weather Service's Climate Prediciton Center.) Some forecast models are predicting a rapid onset of La Niña conditions between March and May.
"With the potential for a rapid transition to La Niña conditions in the next few months, the odds of a wet spring are certainly not improving," says Klaus Wolter, of NOAA's Climate Diagnostics Center. A rapid demise of El Niño like we've seen does not favor wet springs in the West. "If we were to see the emergence of La Niña conditions later this spring, the threat of renewed drought conditions would increase even more."
Now, a paper by Mark Serreze, a senior researcher at the University of Colorado's National Snow and Ice Data Center, suggests new reasons why the future may bring even more frequent and prolonged droughts. According to Serreze's paper in the March 16 issue of Science (abstract here , and press release here), declines in Arctic sea ice, which may have already reached a "tipping point," could trigger changes in weather patterns that would favor reduced rainfall in the West. "Just how things will pan out is unclear, but the bottom line is that Arctic sea ice matters globally," Serreze says.
Snow, ice and cold temperatures have given way quickly to abnormal warmth and mostly dry conditions here in the Front Range of Colorado. My precious silver maple in the back yard is already flowering. A bit early, I think.
-- Tom Yulsman