The congressionally ordered study of global warming and Western water resources is being called the first of its kind by Interior Department officials because it examines eight Western water basins, including the Central Valley and those served by the Colorado, Missouri and Columbia rivers, among others.
The study anticipates average temperatures rising between 5 and 6 degrees Fahrenheit through the 21st century. The federal scientists do not, however, wade into the political thicket of assessing blame for why the Earth is warming.
Some consequences are easier to predict than others, including "more frequent rainfall events (and) less frequent snowfall events." Even within regions, though, the changes will vary. Rainfall, for instance, is expected to increase slightly in the northern part of the Central Valley. In the Valley's southern part, it's expected to decrease slightly.
Similarly, the region's future snowpack will shrink more in some places than in others. Snow will melt readily in the northern Sierra Nevada and in the lower to middle elevations of the southern Sierra range, where winter temperatures already hover on the edge of freezing.
"However, even in the highest elevations of the southern Sierra Nevada, (snowpack) losses are projected to be significant by the late 21st century," the report states.
While avoiding firm predictions about future California flooding, scientists say their studies "raise questions … (about) potentially greater flood risk during the 21st century." These dangers include "more winter runoff" and "more extreme runoff events," the report says.
Read more: http://www.sacbee.com/2011/04/26/3578242/us-study-says-rising-temperatures.html#ixzz1KfpVRCcL