The continuing discussion gives another reason to build the Auburn Dam to capture more of the less water being predicted.
An excerpt.
Article Last Updated: 9/15/2006 02:48 AM
Scientists link area pollution to reduced Sierra snowfall
Findings suggest tainted clouds drop 10-25 percent less rain
By Ian Hoffman, STAFF WRITERInside Bay Area
SACRAMENTO — Scientists say bits of air pollution as small as one-thousandth of a hair's width appear to be reducing rain and snowfall in the Sierra, Cascades and Rockies, potentially adding to threats of water shortages tied to global warming.
Three years ago, Israeli cloud physicist Daniel Rosenfeld saw clues in data from a National Aeronautics and Space Administration satellite that tiny airborne grime released by everything from diesel trucks to cattle was affecting clouds and precipitation downwind of cities.
Now other scientists are finding the same phenomenon worldwide, from France to South Africa, and have witnessed the effects in flights over Sacramento, San Francisco, Oakland and the Sierra foothills.
Rosenfeld and colleagues are finding that polluted clouds drop 10 percent to 25 percent less rain and snow on mountains nearest to the Bay Area, Seattle, Salt Lake City, Tucson, Ariz., and Denver.
In the rest of Northern California, where the air is clean, there is no suppression of rain and snow in the nearest mountains, he said Thursday at the California Energy Commission's third annual conference on climate change.
"We've established that the amount of precipitation can change with what we put in the clouds," said Rosenfeld, chairman of the atmospheric sciences program at the Hebrew University of Jerusalem.
A few years ago, state officials considered the possibility of pollution having an impact on water supplies dubious. But those doubts are fading as the evidence mounts.
"I'm more and more convinced," said Guido Franco, a climate research manager at the state energy commission who funded the closer examination of clouds over the Bay Area.
Scientists say global warming already is shrinking the usual winter snowfall season and hastening snowmelt in the Sierra. That snow supplies most of California's water for farms and cities. As emissions of greenhouse gases rise and California warms, the northern Sierra will warm more than most of the state, and computer simulations show as much as 80 percent of that snowpack vanishing by the end of the century.
Those computer simulations do not account for thinner rain and snowfall related to air pollution, Franco said. That raises the possibility of saving water in California and other Western cities by cleaning up the air.
"In theory," Franco said, "we might be talking about a mitigation strategy" for global warming.
