NASA Study Finds Warmer Future Could Bring DroughtsFebruary 14, 2007NASA scientists may have discovered how a warmer climate in the future could increase droughts in certain parts of the world, including the southwest United States. The researchers compared historical records of the climate impact of changes in the sun's output with model projections of how a warmer climate driven by greenhouse gases would change rainfall patterns. They found that a warmer future climate likely will produce droughts in the same areas as those observed in ancient times, but potentially with greater severity. "These findings strongly suggest that greenhouse gases and long-term changes in solar activity both can have major influences on climate via similar processes," said Drew Shindell, NASA Goddard Institute for Space Studies, New York. Shindell is lead author of a paper that appeared in the Dec. 27, 2006, issue of the American Geophysical Union's "Geophysical Research Letters." "There is some evidence that rainfall patterns already may be changing," Shindell added. "Much of the Mediterranean area, North Africa and the Middle East rapidly are becoming drier. If the trend continues as expected, the consequences may be severe in only a couple of decades. These changes could pose significant water resource challenges to large segments of the population." Using the NASA Goddard Institute for Space Studies climate model, researchers found that changes in solar output in the ancient past increased surface warming and altered atmospheric moisture and circulations. These changes likely led to the severe droughts seen in paleoclimate records. The same model showed that greenhouse-gas warming has similar effects on the atmosphere, suggesting drier conditions may become more common in the subtropics. Rainfall could decrease further in already water-stressed regions such as the southwest United States, Mexico, parts of North Africa, the Middle East, and Australia. Meanwhile, precipitation may increase across the western Pacific, along much of the equator and in parts of southeast Asia. The computer model considers changes in the oceans, weather, and chemistry of the atmosphere, like ozone concentrations, and accurately reproduced the broad rainfall shifts toward regionally drier or wetter conditions during the past several hundred years. Sunspot and ice core data also link the historical rainfall shifts to variations in the amount of energy released by the sun. Since the size of solar changes is uncertain, the study focused on the location and pattern of precipitation shifts, not their precise amount. Increases in solar output break up oxygen molecules, raising ozone concentrations in the upper atmosphere. This adds to upper atmospheric heating that leads to shifts in circulations down to the surface. In turn, surface temperatures warm, and the Earth's basic rainfall patterns are enhanced. For instance, in wet regions such as the tropics, precipitation usually increases, while dry areas become more prone to drought since rainfall decreases and warmer temperatures help remove the small amount of moisture in the soil. "Precipitation is hard to predict because it is so highly variable, but these results increase our confidence that continued warming will be associated with large-scale changes in rainfall," said Shindell. Researchers also considered numerous tree-ring, fire, and lake sediment records from across the Americas, including Mexico, Peru, and the Yucatan Peninsula. These data are reliable indicators of historical climate and confirm a pronounced increase in drought frequency in the southern United States, Mexico, and other subtropical locations during periods of increased solar output in the past 1,200 years. This long-term record of solar output is based on chemical isotopes whose production is related to the sun's brightness. Conversely, in parts of the tropics, ocean sediment data, key indicators of precipitation changes, reflect increased rainfall. According to the researchers, the same processes identified by this new research very likely also affected past civilizations, such as the Pueblo people of New Mexico and Arizona who abandoned cities in the 1300s. For information about NASA and agency programs on the Web, visit: http://www.nasa.gov/home NASA |
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| Related Drought Current Events and Drought News Articles Time of day matters to thirsty trees, U of T researcher discovers The time of day matters to forest trees dealing with drought, according to a new paper produced by a research team led by Professor Malcolm Campbell, University of Toronto Scarborough's vice-principal for research and colleagues in the department of cell and systems biology at the St. George campus. Scientists at UA, collaborating institutions decode maize genome Scientists from the University of Arizona led by Arizona Genomics Institute director Rod A. Wing and from collaborating institutions have deciphered the complete genetic code of the maize plant for the first time. UCR plant scientist's research spawns new discoveries showing how crops survive drought Breakthrough research done earlier this year by a plant cell biologist at the University of California, Riverside has greatly accelerated scientists' knowledge on how plants and crops can survive difficult environmental conditions such as drought. New explanation for nature's hardiest life form Got food poisoning? The cause might be bacterial spores, en extremely hardy survival form of bacteria, a nightmare for health care and the food industry and an enigma for scientists. New Water Management Tool May Help Ease Effects of Drought Continued improvement of climate forecasts is resulting in better information about what rainfall and streamflow may look like months in advance. Drought resistance explained Much as adrenaline coursing through our veins drives our body's reactions to stress, the plant hormone abscisic acid (ABA) is behind plants' responses to stressful situations such as drought, but how it does so has been a mystery for years. Hybrid bluegrasses analyzed for use in transition zone The transition zone can be one of the most challenging places to maintain high-quality turfgrass; changeable growing conditions in these regions often prove too hot for some grasses and too cold for others. Finding turfgrass that thrives in these challenging environments can be perplexing for turf management professionals and homeowners alike. Monash study suggests rainwater is safe to drink A world first study by Monash University researchers into the health of families who drink rainwater has found that it is safe to drink. Wolves lose their predatory edge in mid-life, new U of Minnesota study shows Although most wolves in Yellowstone National Park live to be nearly six years old, their ability to kill prey peaks when they are two to three, according to a study led by Dan MacNulty and recently published online by Ecology Letters. Team led by Scripps Research and UC San Diego scientists reveals secrets of drought resistance A team of biologists in California led by researchers at The Scripps Research Institute and the University of California (UC), San Diego has solved the structure of a critical molecule that helps plants survive during droughts. More Drought Current Events and Drought News Articles |
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