Thursday, November 10, 2011

Global Warming Driving Extreme Weather

For a world already weary of weather catastrophes, the latest warning from top climate scientists paints a grim future: More floods, more heat waves, more droughts and greater costs to deal with them.

A draft summary of an international scientific report obtained by The Associated Press says the extremes caused by global warming could eventually grow so severe that some locations become "increasingly marginal as places to live."

The report from the Nobel Prize-winning Intergovernmental Panel on Climate Change marks a change in climate science, from focusing on subtle shifts in average temperatures to concentrating on the harder-to-analyze freak events that grab headlines, hurt economies and kill people.

"The extremes are a really noticeable aspect of climate change," said Jerry Meehl, senior scientist at the National Center for Atmospheric Research. "I think people realize that the extremes are where we are going to see a lot of the impacts of climate change."

The report says scientists are "virtually certain" — 99 percent — that the world will have more extreme spells of heat and fewer of cold. Heat waves could peak as much as 5 degrees hotter by mid-century and even 9 degrees hotter by the end of the century.

From June to August this year in the United States, blistering heat set 2,703 daily high temperature records, compared with only 300 cold records during that period. That made it the hottest summer in the U.S. since the Dust Bowl of 1936, according to Weather Underground Meteorology Director Jeff Masters, who was not involved in the study.

While rains in October brought some relief to parts of Texas, further drought is forecast, which will add to agricultural losses already exceeding $5 billion. The bigger question is whether the Texas drought is a harbinger of things to come for the entire Southwest - and if so, what the broader impact on Americans living in the region will be.

Climate models indicate that the Southwest will get drier in the coming decades, threatening water supplies already under pressure from a growing population and ageing infrastructure.

The most alarming projections come from a team led by Richard Seager of Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York. They ran 19 climate simulations, averaged out across the entire Southwest, and came to a stark conclusion: that conditions matching the 1930s Dust Bowl and the multi-year droughts of the 1950s "will become the new climatology of the American Southwest" within decades

Water infrastructure can be overhauled, and this is what some states - Texas included - are planning. But their proposals mostly do not allow for what climate change may bring. The latest draft of the Texas State Water Plan, for instance, assumes that between now and 2060 the most severe drought it will face will match the worst on record, from 1950 to 1956. The Intergovernmental Panel's pending report suggests the the worst Texas drought on record is become the new normal with periods of even more extreme drought conditions occurring from that new normal.

The final version of the report from a Intergovernmental panel of leading climate scientists will be issued in a few weeks. The draft says there is at least a 2-in-3 probability that climate extremes have already worsened because of man-made greenhouse gases.

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