Global warming tied to risk of weather extremesJul-11-2012
Last year brought a record heat wave to Texas, massive floods in Bangkok and an unusually warm November in England. How much has global warming boosted the chances of events like that?
Quite a lot in Texas and England, but apparently not at all in Bangkok, say new analyses released Tuesday.
Scientists can't blame any single weather event on global warming, but they can assess how climate change has altered the odds of such events happening, Tom Peterson of the National Oceanic and Atmospheric Administration told reporters in a briefing. He's an editor of a report that includes the analyses published by the Bulletin of the American Meteorological Society.
In the Texas analysis, researchers at Oregon State University and in England noted that the state suffered through record heat last year. It happened during a La Nina weather pattern, the flip side of El Nino. Caused by the cooling of the central Pacific Ocean, La Nina generally cools global temperatures but would be expected to make the southern United States warmer and drier than usual. But beyond that, the scientists wondered, would global warming affect the chances of such an event happening?
To find out, they studied computer climate simulations for La Nina years, focusing on Texas. They compared the outcome of three such years in the 1960s with that of 2008. They used 2008 because their deadline for the study didn't allow enough time to generate thousands of new simulations with fresh data from 2011. The two years were similar in having a La Nina and in amounts of greenhouse gases in the air.
The idea of the study, they said, was to check the likelihood of such a heat wave both before and after there was a lot of man-made climate change, which is primarily from burning fossil fuels like coal and oil.
Their conclusion: Global warming has made such a Texas heat wave about 20 times more likely to happen during a La Nina year.
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Posted by Ken at 4:50 AM
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