http://www.insidedenver.com/drmn/sta...750406,00.html

More rain, little benefit predicted
Increased moisture over next 100 years expected to be lost to
evaporation

By Todd Hartman, Rocky Mountain News
February 17, 2003

Drought-weary Coloradans may want to get used to life without lawns.

A leading climate researcher predicts that the state, along with the
rest of the West, will get more rain and snow as the planet warms over
the next 100 years, but evaporation and parched soils will quickly
drink up the moisture - more than erasing the benefit of greater
precipitation.

That scenario is part of the seemingly paradoxical nature of global
warming, which will put more water vapor into the air, but leave many
regions drier than they were over the past 1,000 years, the researcher
said Sunday at the American Association for the Advancement of Science
meeting in Denver.

Warren Washington, senior research scientist for the National Center
for Atmospheric Research in Boulder, said that increasingly precise
computer models show the planet warming by a range of nearly 3 to 11
degrees Fahrenheit by the year 2100.

The bulk of that temperature rise appears linked to human combustion
of fossil fuels, which is loading the atmosphere with heat-trapping
greenhouse gases, particularly carbon dioxide, Washington said, a
conclusion supported by an international panel of scientists, and more
recently by a 2001 assessment from the National Academy of Sciences.

Since 1870, global temperatures have risen about 1.25 degrees, but
almost a full degree of that came in the past 25 years, he said. That
sudden rise, and the sharper rise expected by 2100, contrasts with a
relatively stable temperature pattern over the past millennium.

"Recent experiments and routine monitoring have found evidence of
global climate changes already occurring that are much larger than can
be explained by the climate's natural variability," Washington said.

Climate models are increasingly sophisticated, and scientists have
increasing confidence in their predictions, Washington said. One key
reason: The models, when fed climate data from the past, accurately
predict current conditions.

One supercomputer, the so-called Earth Simulator in Japan, can do an
unprecedented 35 trillion calculations per second and sports an annual
electricity bill of $12 million. That, and other models, are all
churning out varying predictions of the planet's warming, with the
bulk of forecasts in the range of 3.6 to 7.2 degrees over the next
century, he said.

Washington focused on the global picture, but offered a broad view
about the fate of the Rocky Mountain region.

"There'll be more precipitation, but evaporation tends to win out,"
Washington said. "It will be drier in terms of soil moisture and river
flows."

He cautioned that Colorado's current drought is less likely linked to
global warming, but more to cycles involving the interplay of ocean
temperatures and production of storm systems.

Washington, an NCAR researcher for 40 years, said public policy should
employ a combination of scaling back on greenhouse gas emissions and
"adapting" to a changing climate. Adaptation is necessary, he said,
because the climate will keep warming no matter what the world does in
the near term, noting that a carbon dioxide molecule emitted today
remains in the atmosphere for 90 to 100 years.

But, he added, we should start chipping away at the problem now to
lessen the impact for those who follow.

"If we don't deal with it," he said, "this problem is going to be
enormous in terms of our future."