February 16, 2004
Global warming to squeeze Western mountains dry by 2050
SEATTLE — Global warming will diminish the amount of water
stored as snow in
the Western United States by up to 70 percent in the coastal mountains over the next
50 years, according to a new climate change model released here today.
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
"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 thepast
50 years coastal mountain ranges have already lost 60 percent of their snowpack.
"The change in the timing of the water flow is not
welcome," Leung said.
"The rules we have now for managing dams and reservoirs and irrigation
schedules cannot mitigate for the negative effects of climate change."
If this picture isn't bleak enough, Leung noted that the
model does not even
address the possibility of population growth and increased demand on water
resources. Mountain streams supply power and drinking water to Seattle,
Portland and the San Francisco Bay Area and points south in densely populated
Northern California, and they feed the booming agricultural industries in the
Columbia and Willamette valleys of Washington and Oregon and the San Joaquin
Valley in California.
If there is any good news, it can be found farther east, in
There, the winters are so much colder that small temperature increases
have will have less effect on the snowpack, Leung said.
PNNL is a DOE Office of Science research center that
fundamental understanding of complex systems and provides science-based
solutions in national security, energy, chemistry, the biological sciences and
environmental quality. Battelle, based in Columbus, Ohio, has operated PNNL
for DOE since 1965.