The reduction in Western mountain snow cover, from the Sierra Nevada range that feeds California in the south to the snowcapped volcanic peaks of the Cascades in the Pacific Northwest, will lead to increased fall and winter flooding, severe spring and summer drought that will play havoc with the West's agriculture, fisheries and hydropower industry.
"And this is a best case scenario," said the forecast's chief modeler, L. Ruby Leung, a staff scientist at the Department of Energy's Pacific Northwest National Laboratory in Richland, Wash. Leung delivered the sobering report at the American Association for the Advancement of Science annual meeting, and the full results of her study will appear soon in the journal Climatic Change, now in press.
Leung emphasized the estimate's conservativeness, noting that the climate projections of warming devised by DOE and the National Center for Atmospheric Research are on the low end compared to most other models. Leung's clumping of the models is part of the DOE's Accelerated Climate Prediction Initiative, or ACPI.
ACPI assumes a 1 percent annual increase in the rate of greenhouse gas concentrations through the year 2100, for little change in precipitation and an average temperature increase of 1.5 to 2 degrees centigrade at least through the middle of 21st century. The result: more winter precipitation falling as rain instead of snow, two-tenths of an inch to more than half an inch a day, pushing the snowline in the mountains up from 3,000 feet to higher than 4,000 feet.
Where we now have snow in the mountains into April, "at mid-century snow will melt off much earlier than that," Leung said, noting research that shows in the past 50 years coastal mountain
Contact: Bill Cannon
DOE/Pacific Northwest National Laboratory