Scientists Foresee Extreme Drought Impacts by 2030
Future droughts will be shockers, study says
1970s Sahel disaster will seem mild compared to areas by 2030s, models project
msnbc.com staff and news service reports, Oct. 20, 2010
Increasingly dry
conditions across much of the globe — including the U.S. — are likely
over the next 30 years, a new study predicts. Moreover, by the year 2100
drought in some regions could be unprecedented in modern times.
Increasing
drought has long been forecast as a consequence of warming temperatures,
but the study from the National Center for Atmospheric Research
projects serious impacts as soon as the 2030s. Impacts by century's end
could go beyond anything in the historical record, the study suggests.
"We are facing
the possibility of widespread drought in the coming decades, but this
has yet to be fully recognized by both the public and the climate change
research community," study author Aiguo Dai said in a statement. "If
the projections in this study come even close to being realized, the
consequences for society worldwide will be enormous."
To get an idea of
how severe droughts might get, scientists use a measure called the
Palmer Drought Severity Index, or PDSI. A positive score is wet, a
negative score is dry and a score of zero is neither overly wet nor dry.
The most severe drought in recent history, in the Sahel region of western Africa in the 1970s, had a PDSI of -3 or -4.
By contrast, the
study indicates that by 2100 some parts of the U.S. could see -8 to -10
PDSI, while Mediterranean areas could see drought in the -15 or -20
range.
"Historical PDSI
for the last 60 years show a drying trend over southern Europe but
nothing like those values at the end of this century," Dai said.
"Decadal mean values of PDSI have not reached -15 to -20 levels in the
past in any records over the world."
By the 2030s, the central and western U.S. could see average readings dropping to -4 to -6, the study projected.
Areas likely to experience significant drying include:
-
the western two-thirds of the United States;
-
much of Latin America, especially large parts of Mexico and Brazil;
-
regions bordering the Mediterranean Sea;
-
large parts of southwest Asia;
-
southeast Asia, including China and neighboring countries;
-
most of Africa and Australia.
While Earth is
expected to get dryer overall, some areas will see a lowering of the
drought risk. These include: much of northern Europe; Russia; Canada;
Alaska; and some areas of the Southern Hemisphere.
That doesn't
necessarily mean that agriculture will migrate from the drought areas to
these places in the high latitudes, Dai wrote.
"The
high-latitude land areas will experience large changes in terms of
warmer temperatures and more precipitation, and thus may indeed become
more habitable than today," he wrote. "However, limited sunshine, short
growing season, and very cold nighttime temperature will still prevent
farming over most of these high-latitude regions."
The study's
findings are based on 22 computer models and the best current
predictions of climate-warming greenhouse gas emissions. This could
change depending on actual greenhouse emissions in the future as well as
natural climate cycles such as El Nino, Dai said.
The study appears
this week in the journal Wiley Interdisciplinary Reviews: Climate
Change. It was supported by the National Science Foundation.
Reuters contributed to this report.
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