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Climate control
Meteorology researchers find impact of global climate patterns on
deforestation.
Tsing-chang "Mike" Chen will readily admit that he doesn’t know
much about deforestation.
That is why after all, that he enlisted the expertise of fellow atmospheric
sciences professor Gene Takle in a recent study.
Takle was equally as complimentary about Chen.
"He (Chen) has been working on these kind of issues for several years,"
said Takle, professor of geological and atmospheric sciences. "In this
type of research, you need several decades of data to see if the type of
trends we found continue. That's where Mike's analysis is extremely good.
He’s looked over a long period of time."
Chen, professor of geological and atmospheric sciences, and Takle, along
with graduate students Jin-ho Yoon and Kathryn St. Croix, have described
their research in the October issue of the Bulletin of the American Meteorological
Society. Their work is the first study to consider interdecadal changes
(changes which occur over decades at a time) in deforestation data.
The ISU researchers found that global climate patterns are reducing the
effects of deforestation in the Amazon Basin of South America. Massive deforestation
is generally thought to have a general warming and drying of the landmass
in that area of the world.
"When you cut down all the trees and vegetation in an area like the
Amazon Basin, you would expect that evaporation and subsequent rainfall
would be substanially reduced," Takle said. "Everyone accepts
that under deforestation the Amazon will get warmer and drier."
Chen and Takle's study of the climate from 1950-90, says the exact opposite
is true - that a 20 percent increase in rainfall has occurred. And they
attribute it to global climate patterns. Their research is based on data
from the Global Historical Climatology Network, data gathered on outgoing
long-wave radiation (satellite data to estimate precipitation), and of NCEP-NCAR
re-analysis data (surface- and balloon-based measurements) over the Amazon
Basin.
There are other factors that researchers have to consider according to the
Iowa State meteorologists. Water vapor is converging globally in tropical
South America causing the increase in rainfall during the 40-year time period.
When looking at the effects of deforestation on the Amazon Basin, Chen and
Takle say experts must also look at the effects of long-term global climate
patterns on the area.
Climate patterns could have important implications on a variety of issues
including determining the true effects of deforestation and reforestation
efforts to altering soil erosion and the ability of species to re-emerge
in altered areas.
Chen and Takle’s research indicates that interdecadal changes are indeed
having a profound effect on the Amazon Basin.
"Many scientists have studied the effects of deforestation, but no
one has paid much attention to interdecadal change," Chen aid. "That
is a very important component missing from the studies. It needs to be considered
to get a true reading of the effects of deforestation."
"We believe that deforestation by itself will cause warming and drying
of the Amazon region," Takle said. "But over the past 40 years,
global circulation patterns have been pumping extra moisture into this region
from the outside.
"We don't know when this present pattern will change. It can't continue
forever," he said. "If and when that happens, the deforestation
drying that everyone expected will be made even worse by the drying due
to the reversal of the global circulation. There may be drought never before
experienced in this region. We likely will see effects much worse than those
described by current deforestation-impact models."
Tsing-chang "Mike" Chen and Gene Takle
Around LAS
November 26 to December 2, 2001
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