Wednesday, October 20, 2010

Study predicts Extreme Drought conditions worsening globally with climate change

Extreme Drought and aridity is likely to increase within decades across much of Africa, Australia, North and South America, South west Asia, and around the Mediterranean Sea according to a new study by National Center for Atmospheric Research (NCAR) scientist Aiguo Dai.

Earlier research published in 2005 by Aiguo Dai and scientists at the National Center for Atmospheric Research (NCAR) in the USA found that Global Warming is a major factor in Drought increasing globally.

Dai used 22 computer climate models and a comprehensive index of drought conditions, as well as analyses of previously published studies for his review. Extreme drought may reach such a scale in some regions by the end of the century that has rarely, if ever, been observed in modern times.


The world's most densely populated regions and substantial agricultural productivity lands will be threatened with severe drought conditions, threatening food security. In contrast, higher-latitude regions from Alaska to Scandinavia, and portions of the southern hemisphere are likely to become more moist and available for agricultural use, although not nearly enough to compensate the loss of tropical and temperate agricultural productivity.

"This research does an excellent job of placing future warming-induced drought in the context of the historical drought record," says Eric DeWeaver, program director in NSF's Division of Atmospheric and Geospace Sciences, which funds NCAR. "The work argues credibly that the worst consequences of global warming may come in the form of reductions in water resources."

Dai's study indicates that most of the western two-thirds of the United States will be significantly drier by the 2030s.

"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," Dai said. "If the projections in this study come even close to being realized, the consequences for society worldwide will be enormous."

The global land areas are predicted to be drier overall. While the Western United States faces the possibility of extreme drought, other countries and continents that could face significant drying include:

* Much of Latin America, including large sections of Mexico and Brazil
* Regions bordering the Mediterranean Sea, which could become especially dry
* Large parts of Southwest Asia
* Most of Africa and Australia, with particularly dry conditions in regions of Africa
* Southeast Asia, including parts of China and neighboring countries
* The study also finds that drought risk can be expected to decrease this century across much of Northern Europe, Russia, Canada, and Alaska, as well as some areas in the Southern Hemisphere.

"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 explained.

The 2007 assessment by the Intergovernmental Panel on Climate Change (IPCC) concluded that subtropical areas will likely have precipitation declines, with high-latitude areas getting more precipitation.

In Australia the CSIRO and Bureau of Meteorology have warned for several years that Australia to get hotter, wetter, with more extreme weather. In March 2010 scientists from the CSIRO and Bureau of Meteorology released a joint statement affirming Australia's climate was already changing with a distinct trend in increasing mean temperatures and a change in annual rainfall patterns.

More Information:
* Read the full study: Dai, A. , Drought under global warming: a review. Wiley Interdisciplinary Reviews: Climate Change, n/a. doi: 10.1002/wcc.81
* Science Daily Media Release, Oct 19, 2010 - Drought May Threaten Much of Globe Within Decades, Analysis Predicts

Image Caption
Image: Future drought: These four maps illustrate the potential for future drought worldwide over the decades indicated, based on current projections of future greenhouse gas emissions. These maps are not intended as forecasts, since the actual course of projected greenhouse gas emissions as well as natural climate variations could alter the drought patterns. The maps use a common measure, the Palmer Drought Severity Index, which assigns positive numbers when conditions are unusually wet for a particular region, and negative numbers when conditions are unusually dry. A reading of -4 or below is considered extreme drought. Regions that are blue or green will likely be at lower risk of drought, while those in the red and purple spectrum could face more unusually extreme drought conditions. (Credit: Courtesy Wiley Interdisciplinary Reviews, redrawn by UCAR, republished from Sciencedaily)