Yahoo News 20 Oct 10;
WASHINGTON (AFP) – Large swathes of the planet could experience extreme drought within the next 30 years unless greenhouse gas emissions are cut, according to a study released Tuesday.
"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," said National Center for Atmospheric Research (NCAR) scientist Aiguo Dai, who conducted the study.
"If the projections in this study come even close to being realized, the consequences for society worldwide will be enormous," he said.
Parts of Asia, the United States, and southern Europe, and much of Africa, Latin America and the Middle East could be hit by severe drought in the next few decades, with regions bordering the Mediterranean Sea seeing "almost unprecedented" drought conditions, the study says.
"Severe drought conditions can profoundly impact agriculture, water resources, tourism, ecosystems, and basic human welfare," says the study, published in Wiley Interdisciplinary Reviews: Climate Change.
In the United States, drought causes six to eight billion dollars in damages a year on average, and drought-related disasters killed more than half a million people in Africa in the 1980s, the study says.
While vast areas of the world will become extremely dry for long periods, higher-latitude regions from northern Europe to Russia, Canada, Alaska and India could become wetter.
Increased moisture in those regions would not, however, make up for the drier conditions across much of the rest of the world.
"The increased wetness over the northern, sparsely populated high latitudes can't match the drying over the more densely populated temperate and tropical areas," Dai said.
Dai used results from 22 computer models used by the Nobel Prize-winning Intergovernmental Panel on Climate Change (IPCC), to make projections about temperature, precipitation, humidity and other climate factors based on current projections of greenhouse gas emissions.
Maps of the world that Dai produced using the data show "severe drought by the 2060s over most of Africa, southern Europe and the Middle East, most of Americas (except Alaska and northern Canada, Uruguay, and northeastern Argentina), Australia, and Southeast Asia," the study says.
The maps also show that most of central and northern Eurasia, Alaska and northern Canada, and India would become wetter over the same period.
The study's predictions are based on current projections of what greenhouse gas emissions will be this century.
What actually happens in the next few decades will depend on several factors, including the actual future level of greenhouse gas emissions and natural climate cycles such as El Nino, which often reduces precipitation over low-latitude land areas.
The study follows on from earlier research, including by Dai and the IPCC, that found that global warming will probably alter precipitation patterns as the subtropics expand.
Drought could hit world's populous areas - study
* South Europe, Latin America among driest areas by 2100
* Russia, Canada will see more moisture
* Unprecedented drought possible by century's end
Deborah Zabarenko, Reuters AlertNet 19 Oct 10;
WASHINGTON, Oct 19 (Reuters) - Some of the world's most populous areas -- southern Europe, northern Africa, the western U.S. and much of Latin America -- could face severe, even unprecedented drought by 2100, researchers said on Tuesday.
Increasing drought has long been forecast as a consequence of climate change, but a new study from the U.S. National Center for Atmospheric Research projects serious impact by the 2030s. Impacts by century's end could go beyond anything in the historical record, the study suggests.
To get an idea of how severe the drought 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.
As an example, 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 new study indicates some areas with high populations could see drought in the -15 or -20 range by the end of the century.
"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," study author Aiguo Dai said in answer to e-mailed questions. "Decadal mean values of PDSI have not reached -15 to -20 levels in the past in any records over the world."
A GENERALLY DRIER WORLD
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, and
-- 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 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, the center said in a statement.
More information and graphics on the study can be seen at https://www2.ucar.edu/news/climate-change-drought-may-threaten-much-globe-within-decades .
(Editing by Paul Simao)
