Drought is spreading, study finds | VailDaily.com

Drought is spreading, study finds

Bob Berwyn

As the evidence for human-caused climate disruption keeps mounting, scientists in Colorado are pinpointing some of the effects. In a recent study, Boulder’s National Center for Atmospheric Research determined that the percentage of Earth’s land area stricken by serious drought has more than doubled from the 1970s to the early 2000s.The center’s researchers reported widespread drying over much of Europe and Asia, Canada, western and southern Africa, and eastern Australia. Rising global temperatures appear to be a major factor, says Aiguo Dai, lead author of the study. Dai said the fraction of global land experiencing very dry conditions rose from about 10 percent to 15 percent in the early 1970s to about 30 percent by 2002. Almost half of that change is due to rising temperatures rather than decreases in rainfall or snowfall, Dai said. At the same time, the amount of water vapor in the air has increased and average global precipitation has risen slightly, suggesting that the moisture is evaporating from land areas.The researchers also said the United States has not been affected by the trend as much, with moisture increasing, especially in the region between the Rockies and the Mississippi River. In another center study, researchers said global warming will continue for decades, even if humans stopped releasing all carbon dioxide and other greenhouse gases today.Published in the journal Science, the report says sea levels will continue to rise, potentially worsening the damage from extreme high tides and storm surges, and that heat waves, droughts and storms could all become more intense.The longer the delay in stemming so-called greenhouse gases, the more climate change impacts are inevitable, lead researcher Gerald Meehl says.Meehl’s team developed two complex computer models, including variables like human carbon emissions, other pollution, current temperatures and their rate of change, emissions from volcanoes, changes in solar radiation and shifts in the ozone layer. Then the scientists crunched the numbers in different ways, including a simulation showing the outcome if greenhouse-gas emissions had been stabilized in 2000.Even in that scenario, the model projected another 0.5 degrees Celsius of warming by 2100, equaling the warming that has occurred in the 20th century.In a second study, the center used a different model to show that it may not even be possible to lower emissions enough to prevent rising sea levels. Even if all greenhouse gas production were stopped now, the model suggests sea levels could rise another four inches per century.Vail, Colorado

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