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"Global warming making hurricanes stronger"

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  • Chris Robinson
    Associated Press, Monday, August 1, 2005 Global Warming Making Hurricanes Stronger by Joseph B. Verrengia Is global warming making hurricanes more ferocious?
    Message 1 of 1 , Aug 1, 2005
      Associated Press, Monday, August 1, 2005
      Global Warming Making Hurricanes Stronger
      by Joseph B. Verrengia

      Is global warming making hurricanes more ferocious? New research
      suggests the answer is yes. Scientists call the findings both
      surprising and "alarming" because they suggest global warming is
      influencing storms now — rather than in the distant future.

      However, the research doesn't suggest global warming is generating
      more hurricanes and typhoons.


      Palm trees wave and the sea is whipped up by winds caused by
      Hurricane Emily in the seaside town of La Pesca in northeastern
      Mexico July 20, 2005. Hurricane Emily slammed into northeastern
      Mexico and the U.S. border area on July 20, forcing thousands of
      people to run for cover and threatening dangerous mudslides. Photo
      by Andrew Winning/Reuters

      The analysis by climatologist Kerry Emanuel of the Massachusetts
      Institute of Technology shows for the first time that major storms
      spinning in both the Atlantic and the Pacific since the 1970s have
      increased in duration and intensity by about 50 percent.

      These trends are closely linked to increases in the average
      temperatures of the ocean surface and also correspond to increases
      in global average atmospheric temperatures during the same period.

      "When I look at these results at face value, they are rather
      alarming," said research meteorologist Tom Knutson. "These are very
      big changes."

      Knutson, who wasn't involved in the study, works in the National
      Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics
      Laboratory in Princeton, N.J.

      Emanuel reached his conclusions by analyzing data collected from
      actual storms rather than using computer models to predict future
      storm behavior.

      Before this study, most researchers believed global warming's
      contribution to powerful hurricanes was too slight to accurately
      measure. Most forecasts don't have climate change making a real
      difference in tropical storms until 2050 or later.

      But some scientists questioned Emanuel's methods. For example, the
      MIT researcher did not consider wind speed information from some
      powerful storms in the 1950s and 1960s because the details of those
      storms are inconsistent.

      Researchers are using new methods to analyze those storms and others
      going back as far as 1851. If early storms turn out to be more
      powerful than originally thought, Emmanuel's findings on global
      warming's influence on recent tropical storms might not hold up,
      they said.

      "I'm not convinced that it's happening," said Christopher W.
      Landsea, another research meteorologist with NOAA, who works at a
      different lab, the Atlantic Oceanographic & Meteorological
      Laboratory in Miami. Landsea is a director of the historical
      hurricane reanalysis.

      "His conclusions are contingent on a very large bias removal that is
      large or larger than the global warming signal itself," Landsea said.

      Details of Emanuel's study appear Sunday in the online version of
      the journal Nature.

      Theories and computer simulations indicate that global warming
      should generate an increase in storm intensity, in part because
      warmer temperatures would heat up the surface of the oceans.
      Especially in the Atlantic and Caribbean basins, pools of warming
      seawater provide energy for storms as they swirl and grow over the
      open oceans.

      Emanuel analyzed records of storm measurements made by aircraft and
      satellites since the 1950s. He found the amount of energy released
      in these storms in both the North Atlantic and the North Pacific
      oceans has increased, especially since the mid-1970s.

      In the Atlantic, the sea surface temperatures show a pronounced
      upward trend. The same is true in the North Pacific, though the data
      there is more variable, he said.

      "This is the first time I have been convinced we are seeing a signal
      in the actual hurricane data," Emanuel said in an e-mail exchange.

      "The total energy dissipated by hurricanes turns out to be well
      correlated with tropical sea surface temperatures," he said. "The
      large upswing in the past decade is unprecedented and probably
      reflects the effects of global warming."

      This year marked the first time on record that the Atlantic spawned
      four named storms by early July, as well as the earliest category 4
      storm on record. Hurricanes are ranked on an intensity scale of 1 to
      5.

      In the past decade, the southeastern United States and the Caribbean
      basin have been pummeled by the most active hurricane cycle on
      record. Forecasters expect the stormy trend to continue for another
      20 years or more.

      Even without global warming, hurricane cycles tend to be a
      consequence of natural salinity and temperature changes in the
      Atlantic's deep current circulation that shift back and forth every
      40 to 60 years.

      Since the 1970s, hurricanes have caused more property damage and
      casualties. Researchers disagree over whether this destructiveness
      is a consequence of the storms' growing intensity or the population
      boom along vulnerable coastlines.

      "The damage and casualties produced by more intense storms could
      increase considerably in the future," Emanuel said.

      © 2005 Associated Press
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