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CLIMATE COLLAPSE by David Stipp at www.fortune.com

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  • Patrick Neuman
    CLIMATE COLLAPSE Growing Evidence of Scary Change By David Stipp Scientists used to think that major climate changes, like the onset of an ice age, took
    Message 1 of 1 , Feb 3 12:33 PM
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      CLIMATE COLLAPSE
      Growing Evidence of Scary Change
      By David Stipp

      Scientists used to think that major climate changes, like the onset
      of an ice age, took thousands of years to unfold. Now they know such
      dramatic transitions can occur in less than a decade. The probable
      trigger of abrupt climate changes, at least in the Northern
      Hemisphere, is the shutdown of a huge ocean current in the Atlantic
      Ocean. The current is driven by dense, salty water that flows north
      from the tropics and sinks in the North Atlantic. If fresh water is
      pumped into the northerly part of the current—which can occur as
      global warming melts Arctic ice—its salinity drops, making it less
      dense. This diminishing density can prevent the water from sinking in
      the North Atlantic, stopping the current's flow. Much of Europe and
      the U.S. could become colder and drier if that happened.

      Many details of this big picture remain hazy, including whether
      recent global warming threatens to shut down the Atlantic current.
      But over the past few years, scientists have detected disquieting
      trends:

      • In tandem with rising average temperatures across the globe, 3% to
      4% of the Arctic ice cap has melted per decade since about 1970.

      • Recently the Arctic's largest ice shelf broke up near Canada's
      Ellesmere Island, releasing an ice-dammed freshwater lake into the
      ocean. (Scientists believe that the similar melting of an Arctic ice
      dam 8,200 years ago triggered an episode of abrupt climate change.)

      • The North Atlantic's salinity has declined continuously for the
      past 40 years—the most dramatic oceanic change ever measured.

      • The flow of cold, dense water through a North Atlantic channel near
      Norway—part of the great ocean current that warms northern Europe—has
      dropped by at least 20% since 1950, suggesting that the current is
      weakening.

      Scientists still don't know whether a climate disaster is on the way.
      But taken together, these changes appear strikingly similar to ones
      that preceded abrupt climate shifts in the past. Many researchers now
      believe the salient question about such change is not "Could it
      happen?" but "When?"

      From the Feb. 9, 2004 Issue

      http://www.fortune.com/fortune/technology/articles/0,15114,582593,00.h
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