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Sierra Climate Change
Tue Jul 15, 2003
Listen in RealAudio 
Hi, I'm Bryan Yeaton for The Weather Notebook's weekly segment on global climate change. In
the Western US, mountain snowfall is a crucial water storage system, but new research
indicates that a warming atmosphere could seriously impact this reservoir. More from
correspondent Chris Richard.
UCLA climatologist Jinwon Kim predicted the temperature shift by combining global projections
of global climate change and a local model for the Sierra Nevada. Kim also factored in
satellite data that charts changes in local vegetation.
JK: What we see as snow today, much will turn into rain in the altered climate. The snow is a
natural reservoir during winter time. But when it falls as rainfall, you know the Sierra's
character is very steep terrain. So the rain flows into stream channels and quickly flows
downstream.
Kim says rainy weather in the mountains could increase by about 30 percent.
JK: There is limited but pretty well-definded signals that suggest such a change is already
going right now.
Dan Cayan, a climate researcher for the Scripps Institute and the U.S. Geological Survey, says
that means reservoir managers will have to plan for more floods.
DC: There is a big challenge to the way that water is managed to the state now in that heavier
wintertime flows could violate flood control criteria and consequently a lot of water would
have to be released.
In other words, to leave room for possible floods, they'll have to throw water away. Cayan
says Kim's model for the Sierra Nevada could easily apply to the entire West.
Chris Richard reports from Los Angeles. The Weather Notebook is supported by the National
Science Foundation, and Subaru.
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