Study: Global warming to impact Calif. in 20 years

DON THOMPSON
Associated Press Writer
11/08/2003

SACRAMENTO, Calif. -- Global warming will substantially affect California in about 20 years, experts say, warning that the state is more vulnerable because of its coastline, its climate and its dependence on Sierra Nevada snowpack for water and hydroelectricity.

"It's going to affect all of us," said Robert Wilkinson of the University of California, Santa Barbara, School of Environmental Science and Management, who wrote a 432-page treatise on the impact on California.

It means a shorter ski season in the Sierra, and poorer habitat for endangered salmon in lower streams. It may mean more wildfires and more floods. Extreme heat waves, easier spread of diseases and increased air pollution all could imperil health.

Oceans that rose 4 inches to 8 inches over the last century could rise up to 3 feet this century, swamping San Francisco Bay estuaries and endangering pumps sending freshwater from the Sacramento-San Joaquin River Delta to the Bay Area, San Joaquin Valley and Southern California.

It will mean more fights over water throughout the West.

"Climate change is upon us. In 20 to 25 years, we really will be working with a different climate," said Michael Dettinger, a U.S. Geological Survey research biologist and researcher with the Climate Research Division at Scripps Institution of Oceanography.

Every scientific model predicts warmer temperatures, with the bulk projecting an increase in the range of 3 degrees to 6 degrees by 2100. But the computer models split on whether California will become wetter or drier.

Either way, warmer temperatures mean a shift in California's water cycle.

The Sierra snowpack that functions as the state's largest reservoir could shrink by a third by 2060 and to half its historic size by 2090. Runoff that fills reservoirs will start

in midwinter, not spring. And rain falling on snow will trigger more flooding, scientists said Thursday at a seminar hosted by the Water Education Foundation.

Models projecting a drier California predict a sharp increase in critically dry periods, said Alan Hamlet, a water resources engineer with the University of Washington.

"We're going to have exacerbated conflicts over water, both in California and the Colorado Basin" that also supplies six upstream states, he said. Fortunately for California, it is rare -- but not unheard of -- for the Sierra and the Rockies to have a simultaneous drought, so usually there is substantial water for Southern California from one or the other.

The trends are already in play.

Spring temperatures have increased 2 degrees to 3 degrees since 1950, peak spring snowmelt comes two to three weeks sooner, and vegetation blooms one to three weeks earlier and stays green longer, scientists earlier told a state Assembly committee on water and climate change.

While more dams and reservoirs could capture vital runoff and control flooding, there are substantial questions where or if to build them given the uncertain long-range weather pattern forecasts. Experts predicted the state will have to rely more on conserving and reusing water, desalinization, groundwater storage, and water trades and transfers between regions.

As with the ebb and flow of the Ice Age, warmer temperatures mean grass and oak woodlands and chaparral will grow higher into the mountains over the next 100 years, while conifer forests can grow above the current tree line, said Susan Ustin, an environmental and resource science professor at the University of California, Davis.

But 100 years is a blink in geologic time, and the relatively quick change will disrupt ecosystems that need millennia to adapt, she said. Invasive species that already threaten native plants and animals may be quick to fill that void.

Earlier snowmelt means less spring runoff for salmon, and water could get too warm for them to spawn. Already, runoff into the Sacramento River has dropped 11 percent over the last century.

But warmer weather means longer growing seasons, which could help agriculture -- as long as there's enough water for irrigation, said Rick Snyder, a biometeorologist at UC Davis. While many of California's crops could benefit, its famed wine grapes need a precise combination of temperatures and could suffer, said Snyder and Wilkinson.

The effect could come down to "if you're talking white wine or red wine," said Wilkinson. "Is that a great research project, or what?"


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