Climate
Extremes Are Coming, Study Says
Oct 20 6:55 PM US/Eastern
By SETH BORENSTEIN
AP Science Writer
WASHINGTON
The world _ especially the Western United States, the Mediterranean
region and Brazil _ will likely suffer more extended droughts,
heavy rainfalls and longer heat waves over the next century because
of global warming, a new study forecasts.
But the prediction of a future of nasty extreme weather also
includes fewer freezes and a longer growing season.
In a preview of a major international multiyear report on climate
change that comes out next year, a study out of the National Center
for Atmospheric Research details what nine of the world's top
computer models predict for the lurching of climate at its most
extreme.
"It's going to be a wild ride, especially for specific regions,"
said study lead author Claudia Tebaldi, a scientist at the
federally funded academic research center.
Tebaldi pointed to the Western U.S., Mediterranean nations and
Brazil as "hot spots" that will get extremes at their worst,
according to the computer models.
And some places, such as the Pacific Northwest, are predicted to
get a strange double whammy of longer dry spells punctuated by
heavier rainfall.
As the world warms, there will be more rain likely in the tropical
Pacific Ocean, and that will change the air flow for certain areas,
much like El Nino weather oscillations now do, said study co-author
Gerald Meehl, a top computer modeler at the research center. Those
changes will affect the U.S. West, Australia and Brazil, even
though it's on South America's eastern coast.
For the Mediterranean, the issue has more to do with rainfall in
the tropical Atlantic Ocean changing air currents, he said.
"Extreme events are the kinds of things that have the biggest
impacts, not only on humans, but on mammals and ecosystems," Meehl
said. The study, to be published in the December issue of the
peer-reviewed journal Climatic Change, "gives us stronger and more
compelling evidence that these changes in extremes are more
likely."
The researchers took 10 international agreed-upon indices that
measure climate extremes _ five that deal with temperature and five
with precipitation _ and ran computer models for the world through
the year What Tebaldi called the scariest results had to do with
heat waves and warm nights. Everything about heat waves _ their
intensity, length and occurrence _ worsens.
"The changes are very significant there," Tebaldi said. "It's
enough to say we're in for a bad future."
The measurement of warm nights saw the biggest forecast changes.
Every part of the globe is predicted to experience a tremendous
increase in the number of nights during which the low temperature
is extremely high. Those warm night temperatures that should happen
only once every decade will likely occur at least every other year
by the time we reach 2099, if not more frequently, Tebaldi
said.
Warm nights are crucial because Chicago's 1995 heat wave
demonstrated that after three straight hot nights, people start
dying, Meehl said. However, heat wave deaths are decreasing in the
United States because society has learned to adapt better, using
air conditioning, noted University of Alabama at Huntsville
atmospheric sciences professor John Christy. He is one of a
minority of climate scientists who downplay the seriousness of
global warming.
Similarly, the days when the temperature drops below freezing will
plummet worldwide. That's not necessarily a good thing, because
fewer frost days will likely bring dramatic change in wildlife,
especially bug infestation, Tebaldi said.
"It's a disruption of the equilibrium that's been going for many
centuries," Tebaldi said. But she noted that a lengthier growing
season in general is good.
"This notion of the greening of the planet ... generally is a
positive benefit," Christy said.
Christy, who did not participate in the study but acknowledges that
global warming is real and man-made, said an increase in nighttime
low temperatures makes much more sense than the rain-and-drought
forecasts of the paper.
One of the larger changes in precipitation predicted is in the
intensity of rain and snowfall. That means, Tebaldi said, "when it
rains, it rains more" even if it doesn't rain as often.
Tebaldi's assessment jibes with the National Climatic Data Center's
tracking of extreme events in the United States, said David
Easterling, chief of the center's scientific services. Easterling's
group has created a massive climate extreme index that measures the
weather in America. Last year, the United States experienced the
second most extreme year in 95 years; the worst year was in
1998.
