CALIFORNIA

Global Warming Report Predicts Drastic Changes

Tony Russomanno

The first close-up view of global warming predicts disaster for California's drinking water supply, if nothing is done to plan for it.

President Bush is downplaying the EPA report, calling it "something put out by the bureaucracy." But U.C. Santa Cruz professor Lisa Sloan says increases in carbon dioxide will mean a much warmer and dryer state 50 years from now.

The research predicts warming of about four to five degrees in the Bay Area and along the coast. But in the mountains, beyond the moderating influence of the ocean, temperatures may soar.

"Namely, spring and summertime warming of 14 to 15 degrees Fahrenheit," Sloan said.

Computer models also predict there will be much less snow in the Sierra.

"Snowfall, snow pack, will be reduced quite significantly," Sloan said. "It's about an 80% reduction on an annual average basis."

The net effect is that Sierra snow, which now lasts into July, may be gone by April. Say goodbye to spring skiing.

But worse than that, rapid melting combined with lower overall snowfall could mean both floods and droughts regularly, even in the same year.

"If we get all our water, and it comes flowing throughout the system in the springtime ...then we have an excess early in the spring, and then we have a drought later in the year," Sloan said.

The research assumes that carbon dioxide concentrations, caused by the burning of fossil fuels, will continue to increase. But even if the gasses somehow stopped being produced today, it would take centuries for the atmosphere to clean itself, and researchers believe the forecast climate change would still occur. So, as the debate over global warming continues, could it already too late?

"Well, how do you define too late?" Sloan said. "What else are we going to do? It just may be harder to undo it."

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UniSci.Com

Detailed Picture Of Coming California Climate Change

Researchers at the University of California, Santa Cruz, have produced
a detailed picture of how California's climate is likely to change
within the next 50 to 100 years as a result of global warming.

Their study, complete with temperature and precipitation data for
different parts of the state, goes far beyond the usual speculation
about the potential impacts of climate change on the state.

Despite uncertainties in the climate models used to generate these
scenarios, they are valuable tools for planning, said Lisa Sloan, an
associate professor of Earth sciences at UCSC. The findings of Sloan
and her coauthors will be published online on June 7 by the journal
Geophysical Research Letters.

The study supports what many have already guessed -- global warming
will mean warmer temperatures and smaller snowpacks in California,
with serious adverse effects on the state's water supply. But the
study also reveals more subtle details and offers regional specificity
and precise numbers backed by a statistical analysis.

"Everybody has guessed at the effects on water resources, but now we
have numbers and locations. It's a lot different from the standard
arm-waving," Sloan said. "Our hope is that this kind of study will
give state and regional officials a more reliable basis for planning
how to cope with climate change."

Sloan's research group used a sophisticated computer model of the
regional climate system to look at the response of California's
climate to changing concentrations of carbon dioxide, the
heat-trapping "greenhouse gas" released by burning of fossil fuels.

Sloan worked with graduate students Mark Snyder, who is first author
of the paper, and Jason Bell, now a computer programmer in the Earth
Sciences Department, to develop a regional climate model centered over
California.

The regional model offers much finer spatial resolution than larger
models used to study the global climate. Since the regional climate is
driven by global processes, the regional model was coupled with a
global climate model.

The researchers looked at the effects of doubling the amount of carbon
dioxide in the atmosphere compared to the preindustrial level. The
latest projections of carbon dioxide emissions indicate that the
atmospheric concentration will be twice the preindustrial level well
before the end of this century and possibly as soon as 2050.

With atmospheric carbon dioxide doubled, the California regional
climate model showed higher average temperatures every month of the
year in every part of the state. The extent of the warming varied,
however, with the greatest increases in temperature occurring at high
elevations in the Sierra Nevada and the Cascade Range. For example,
the average temperature in June in the Sierra Nevada increased by 11
degrees Fahrenheit.

The model also showed rainfall increasing in northern California but
staying largely the same in southern California, while snow
accumulation in the mountains decreased dramatically. In March, for
example, it showed an additional 8 inches of rain falling in the
central Sierra, while the height of the snowpack at the end of March
dropped by 13 feet. By the end of April, the snowpack was almost
completely gone.

"With less precipitation falling as snow and more as rain, plus higher
temperatures creating increased demand for water, the impacts on our
water storage system will be enormous," Sloan said.

Snyder said this report is only the first step in an ongoing effort to
understand the implications of climate change for California. The
results represent an "average" year, based on 15 years worth of data
generated by the model for each carbon dioxide concentration.
Additional studies will try to capture the natural variability of the
climate and how that variability may change in the future, he said.

"This opens the door for a lot more studies to look at regional
climate change in more detail, and to understand the variability that
is likely to occur," Snyder said. "It's important to consider not only
the average conditions but also what the extremes will be."

The researchers are also exploring refinements in the model that would
yield even higher spatial resolution. Already, the model provides more
detail than any previous study, showing how climate change is likely
to affect different parts of the state, such as the Coast Ranges, the
Central Valley, the Mojave Desert, and the Sierra Nevada.

All of the major features of the results were statistically
significant, Sloan said. She added, however, that the results are not
predictions.

"The model gives us scenarios of what the future may look like," Sloan
said. "There are only two ways to tell how good the model is: One is
to wait for 50 years and see what happens, and the other is to model
the present day. We've done the latter quite rigorously and have
satisfied ourselves that the model does a good job of representing the
present climate. So our confidence in these scenarios is pretty good."

In addition to Sloan, Snyder, and Bell, the paper's authors include
Philip Duffy and Bala Govindasamy, both climate researchers at
Lawrence Livermore National Laboratory. Sloan's research is supported
in part by a fellowship from the David and Lucile Packard Foundation.
- By Tim Stephens

Images can be downloaded from the web at this URL
http://www.ucsc.edu/news_events/download/

[Contact: Lisa Sloan, Tim Stephens]

05-Jun-2002

UniSci.Com