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More rain, little benefit predicted
http://www.insidedenver.com/drmn/sta...750406,00.html
More rain, little benefit predicted Increased moisture over next 100 years expected to be lost to evaporation By Todd Hartman, Rocky Mountain News February 17, 2003 Drought-weary Coloradans may want to get used to life without lawns. A leading climate researcher predicts that the state, along with the rest of the West, will get more rain and snow as the planet warms over the next 100 years, but evaporation and parched soils will quickly drink up the moisture - more than erasing the benefit of greater precipitation. That scenario is part of the seemingly paradoxical nature of global warming, which will put more water vapor into the air, but leave many regions drier than they were over the past 1,000 years, the researcher said Sunday at the American Association for the Advancement of Science meeting in Denver. Warren Washington, senior research scientist for the National Center for Atmospheric Research in Boulder, said that increasingly precise computer models show the planet warming by a range of nearly 3 to 11 degrees Fahrenheit by the year 2100. The bulk of that temperature rise appears linked to human combustion of fossil fuels, which is loading the atmosphere with heat-trapping greenhouse gases, particularly carbon dioxide, Washington said, a conclusion supported by an international panel of scientists, and more recently by a 2001 assessment from the National Academy of Sciences. Since 1870, global temperatures have risen about 1.25 degrees, but almost a full degree of that came in the past 25 years, he said. That sudden rise, and the sharper rise expected by 2100, contrasts with a relatively stable temperature pattern over the past millennium. "Recent experiments and routine monitoring have found evidence of global climate changes already occurring that are much larger than can be explained by the climate's natural variability," Washington said. Climate models are increasingly sophisticated, and scientists have increasing confidence in their predictions, Washington said. One key reason: The models, when fed climate data from the past, accurately predict current conditions. One supercomputer, the so-called Earth Simulator in Japan, can do an unprecedented 35 trillion calculations per second and sports an annual electricity bill of $12 million. That, and other models, are all churning out varying predictions of the planet's warming, with the bulk of forecasts in the range of 3.6 to 7.2 degrees over the next century, he said. Washington focused on the global picture, but offered a broad view about the fate of the Rocky Mountain region. "There'll be more precipitation, but evaporation tends to win out," Washington said. "It will be drier in terms of soil moisture and river flows." He cautioned that Colorado's current drought is less likely linked to global warming, but more to cycles involving the interplay of ocean temperatures and production of storm systems. Washington, an NCAR researcher for 40 years, said public policy should employ a combination of scaling back on greenhouse gas emissions and "adapting" to a changing climate. Adaptation is necessary, he said, because the climate will keep warming no matter what the world does in the near term, noting that a carbon dioxide molecule emitted today remains in the atmosphere for 90 to 100 years. But, he added, we should start chipping away at the problem now to lessen the impact for those who follow. "If we don't deal with it," he said, "this problem is going to be enormous in terms of our future." |
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