Global Warming 37 Percent To Blame For Droughts:
Scientist
Date: 26-Mar-09
Country: SINGAPORE
Author: David Fogarty, Climate Change Correspondent, Asia
Global Warming 37 Percent To Blame For Droughts: Scientist Photo:
REUTERS/Stringer
A man walks past a cement factory on the outskirts of Baokang,
Hubei province February 26, 2009.
Photo: REUTERS/Stringer
SINGAPORE - Global warming is more than a third to blame for a major drop in
rainfall that includes a decade-long drought in Australia and a lengthy dry
spell in the United States, a scientist said on Wednesday.
Peter Baines of Melbourne University in Australia analyzed global rainfall
observations, sea surface temperature data as well as a reconstruction of
how the atmosphere has behaved over the past 50 years to reveal rainfall
winners and losers.
What he found was an underlying trend where rainfall over the past 15 years
or so has been steadily decreasing, with global warming 37 percent
responsible for the drop.
"The 37 percent is probably going to increase if global warming continues,"
Baines told Reuters from Perth in Western Australia, where he presented his
findings at a major climate change conference.
Baines' analysis revealed four regions where rainfall has been declining.
The affected areas were the continental United States, southeastern
Australia, a large region of equatorial Africa and the Altiplano in South
America.
But there were two areas in the tropics where rainfall has been increasing
-- northwestern Australia and the Amazon Basin.
"This is all part of a global pattern where the rainfall is generally
increasing in the equatorial tropics and decreasing in the sub-tropics in
mid-latitudes," Baines said.
"This is a little bit like the pattern that the (computer) models predict
for global warming but this is coming out of the rainfall observations of
the past 30 years," added Baines, of Melbourne University's civil and
environmental engineering department.
The rainfall trend was also accompanied by a trend in global sea surface
temperatures (SST), he said, adding he used temperature data going back to
1910.
Sea surface temperatures have been rising as the atmosphere warms.
"If you take the SST data and analyze that over a long period you can break
that up into a variety of components, such a global warming component," he
said.
He also looked at the influence on rainfall of major ocean circulation
patterns that have a major impact on the world's weather such as the
Atlantic conveyor belt that brings warm temperatures to northern Europe.
Two Pacific circulation patterns, including the Pacific Decadal Oscillation,
were also studied for their influence on rainfall.
The key in the analysis was to strip out the influence of the El Nino
ocean-climate pattern which causes drought in Southeast Asia and Australia
and floods in Chile and Peru.
Baines, who also works for the Department of Earth Sciences at the
University of Bristol in England, said the Atlantic conveyor belt was 27
percent to blame for the decreased rainfall, while the two Pacific ocean
circulation patterns were 30 percent responsible.
(Editing by Dean Yates)
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