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Global Warming to Bring Heavier Rains, Snow

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  • Mike Neuman
    Global warming to bring heavier rains, snow By Michael Kanellos http://news.com.com/Global+warming+to+bring+heavier+rains% 2C+snow/2100-11395_3-5895784.html
    Message 1 of 1 , Jan 9, 2006
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      Global warming to bring heavier rains, snow

      By Michael Kanellos
      http://news.com.com/Global+warming+to+bring+heavier+rains%
      2C+snow/2100-11395_3-5895784.html

      Fri Oct 14 13:36:00 PDT 2005

      In the forecast, more rain and snow.

      Rising temperatures in the world's atmosphere and oceans will lead to
      more intense storms as the century progresses, according to a new
      report from the National Center for Atmospheric Research.

      Evaporation increases when the surface temperature of the ocean rises
      and warmer air can hold more moisture. When this soggier-than-normal
      air moves over land, it results in storms wetter and more intense
      than those experienced in the past.

      The greatest changes will occur over land in the tropics, according
      to the study, which was released Thursday. Heavier rain or snow,
      however, will also fall in northwestern and northeastern North
      America, northern Europe, northern and eastern Asia, southwestern
      Australia, and parts of South America during the current century.

      "The models show most areas around the world will experience more
      intense precipitation for a given storm during this century," lead
      author Gerald Meehl said in a statement. "Information on which areas
      will be most affected could help communities to better manage water
      resources and anticipate possible flooding."

      The Mediterranean and the southwestern U.S., meanwhile, will
      experience a different pattern. Storms will likely become wetter,
      particularly in the fall and winter, but dry spells may stretch for
      longer in the warmer months. A picture of how this pattern might
      develop was seen in Europe this year: While Germany endured
      unprecedented floods, Spain and Portugal imposed water rationing
      because of a lengthy drought.

      Researchers at the Massachusetts Institute of Technology in April
      released a report predicting that hurricanes would become more
      intense over the coming century. It became an oft-cited study after
      Hurricane Katrina hit.

      Climate change has become a hot-button issue for scientists,
      politicians and the general public. The scientific community now
      generally agrees that global warming is in fact happening, and most
      of the future scenarios aren't pretty.

      Rising sea levels could lead to more frequent flooding in Bangladesh
      and other low-lying nations. Food production could also be disrupted.
      Melting polar ice is expected by some to lead to a sea lane above
      Siberia in a few years.

      "Probably most of the climate change in the early part of the century
      was caused by natural events," he said, such as a rebounding of
      temperatures that ordinarily occurs after volcanoes. "But the change
      in the latter part of he 20th century was the result of human
      activity."

      Others disagree. Still others assert that, because the stakes are so
      high, debating whether or not reducing greenhouse gas emissions can
      help makes no sense.

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      http://news.com.com/2102-11395_3-5895784.html?tag=st.util.print


      ------------- Parent Study -------------
      Warmer Seas, Wetter Air Make Harder Rains as Greenhouse Gases Build
      October 13, 2005
      http://www.ucar.edu/news/releases/2005/hardrain.shtml

      BOULDER—Storms will dump heavier rain and snow around the world as
      Earth's climate warms over the coming century, according to several
      leading computer models. Now a study by scientists at the National
      Center for Atmospheric Research (NCAR) explains how and where warmer
      oceans and atmosphere will produce more intense precipitation. The
      findings recently appeared in Geophysical Research Letters, a
      publication of the American Geophysical Union.

      The greatest increases will occur over land in the tropics, according
      to the study. Heavier rain or snow will also fall in northwestern and
      northeastern North America, northern Europe, northern Asia, the east
      coast of Asia, southwestern Australia, and parts of south-central
      South America during the 21st century.

      "The models show most areas around the world will experience more
      intense precipitation for a given storm during this century," says
      lead author Gerald Meehl. "Information on which areas will be most
      affected could help communities to better manage water resources and
      anticipate possible flooding."

      NCAR authors Meehl, Julie Arblaster, and Claudia Tebaldi analyzed the
      results of nine atmosphere-ocean global climate models to explain the
      physical mechanisms involved as intensity increased. Precipitation
      intensity refers to the amount of rain or snow that falls on a single
      stormy day.

      Both the oceans and the atmosphere are warming as greenhouse gases
      build in the atmosphere. Warmer sea surfaces boost evaporation, while
      warmer air holds more moisture. As this soggy air moves from the
      oceans to the land, it dumps extra rain per storm.

      Though water vapor increases the most in the tropics, it also plays a
      role in the midlatitudes, according to the study. Combined with
      changes in sea-level pressure and winds, the extra moisture produces
      heavier rain or snow in areas where moist air converges.

      In the Mediterranean and the U.S. Southwest, even though intensity
      increases, average precipitation decreases. The authors attribute the
      decrease to longer periods of dry days between wet ones. The heavier
      rain and snow will most likely fall in late autumn, winter, and early
      spring, while warmer months may still bring a greater risk of drought.
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