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Earth 'shook off' ancient warming (BBC) added version from: news.scotsman.com

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  • Patrick Neuman
    Same basic story but from http://news.scotsman.com Sun 1 Feb 2004 10:29am (UK) http://news.scotsman.com/latest.cfm?id=2478109 Earth Saves Itself from Global
    Message 1 of 1 , Feb 3, 2004
      Same basic story but from http://news.scotsman.com
      Sun 1 Feb 2004

      10:29am (UK)
      http://news.scotsman.com/latest.cfm?id=2478109

      Earth Saves Itself from Global Warming - over 150,000 Years

      By John von Radowitz, Science Correspondent, PA News

      Scientists have discovered how the Earth saved itself from a severe
      hot flush that struck during the time of the dinosaurs.

      Understanding what happened might have a bearing on the future impact
      of man-made global warming, experts believe.

      It was already known that about 180 million years ago temperatures on
      Earth rapidly shot up by about 5C.

      The cause was a sudden release of huge amounts of methane from the
      sea bed, which quickly transformed to the greenhouse gas carbon
      dioxide in the atmosphere.

      Plants and animals were affected by the sudden change. Scientists
      have found evidence of a marine mass extinction during this period
      that killed off 84% of bivalve shellfish.

      But miraculously, over a period of 150,000 years, the Earth returned
      to normal and life continued to flourish.

      How this occurred has been a mystery until now. But today a team led
      by Dr Anthony Cohen at the Open University in Milton Keynes revealed
      it was weathered rocks that saved the planet from meltdown.

      Dr Cohen said: "Our new evidence has shown that this warming caused
      the weathering of rocks on the Earth's surface to rapidly increase by
      at least 400%.

      "This intense rock-weathering effectively put a brake on global
      warming through chemical reactions that consumed the atmosphere's
      extra carbon dioxide in about 150,000 years.

      "Our findings are of the broadest interest because past events of
      this nature demonstrate how the Earth recovers from large, natural
      perturbations and how the long-term stability of the climate is
      maintained."

      The research appears in the February issue of the American Geological
      Society journal Geology.

      Dr Cohen and his colleagues based their results on geochemical
      studies of organic-rich mudrock samples collected from near Whitby in
      North Yorkshire.

      They discovered that the rock had been subject to high rates of
      weathering caused by the warm and wet conditions during the Jurassic
      hot spell.

      This led to minerals such as calcium and magnesium eroding away and
      pouring into the sea, where they "fixed" carbon dioxide.

      Calcium combined with the gas, for instance, would have formed
      calcium carbonate which could not return to the atmosphere.

      As the process occurred all over the Earth, atmospheric carbon
      dioxide levels slowly reduced and put a halt to rising temperatures.

      Dr Cohen said: "What we have learned from these rocks is how the
      Earth can – over a long time – combat global warming. What we need to
      discover now is why and at what point it goes into combat mode, and
      precisely how long the conflict takes to resolve."

      Some experts believe human global warming might trigger another
      upwelling of methane that puts the climate into overdrive.

      Vast amounts of methane still lie at the bottom of the oceans trapped
      in frozen hydrates.

      If global temperatures reach a critical point, it is possible they
      might suddenly be released into the atmosphere.

      This is what is thought to have occurred 180 million years ago. The
      liberation of methane at that time followed a long period of very
      gradual global warming.

      Dr Cohen said: "The lesson we have learned is that the planet will
      survive such catastrophes, but not every species will survive with
      it."

      --- In Paleontology_and_Climate@yahoogroups.com, npat1@j... wrote:

      "What we have learned from these rocks is how the Earth can, over a
      long time, combat global warming Dr Anthony Cohen, Open University "

      UK scientists claim they now know how Earth recovered on its own from
      a sudden episode of severe global warming at the time of the
      dinosaurs.

      Understanding what happened could help experts plan for the future
      impact of man-made global warming, experts say.

      Rock erosion may have leached chemicals into the sea, where they
      combined with carbon dioxide, causing levels of the greenhouse gas to
      fall worldwide.

      UK scientists report the details of their research in the journal
      Geology.

      About 180 million years ago, temperatures on Earth rapidly shot up by
      about 5 Celsius. The cause is thought to have been a sudden release
      of huge amounts of methane from the sea bed. Methane is itself a
      greenhouse gas but it is short-lived.

      However, it is easily oxidised to carbon dioxide (CO2) which lingers
      in the atmosphere for long periods of time.

      Mass extinction

      Plants and animals were affected by the sudden rise in atmospheric
      CO2. Scientists have found evidence of a marine mass extinction
      during this period that killed off 84% of bivalve shellfish.

      Over a period of about 150,000 years, the Earth returned to normal
      and life continued flourishing. How this happened was a mystery, but
      now scientists from the Open University in Milton Keynes claim to
      have a possible answer.

      "Our new evidence has shown that this warming caused the weathering
      of rocks on the Earth's surface to rapidly increase by at least
      400%," said Dr Anthony Cohen, who led the research.

      "This intense rock-weathering effectively put a brake on global
      warming through chemical reactions that consumed the atmosphere's
      extra carbon dioxide."

      They discovered that intense rock weathering coincided with warm
      conditions and high atmospheric CO2.

      'Methane burp'

      Weathering occurs through the action of rain. Although the
      researchers did not uncover direct evidence for increased
      precipitation, they believe there were no limitations on water during
      the period.

      The warm conditions caused by the "methane burp" would have sped up
      the rate at which weathering occurred. This led to minerals such as
      calcium and magnesium eroding from rocks and pouring into the sea.

      Calcium combined with CO2, for instance, would have caused the
      precipitation of calcium carbonate. This process of CO2 consumption
      would have lowered levels of the greenhouse gas on a global scale.

      As CO2 levels fell, so did global temperatures.

      "Global warming is affecting the climate today, but it's very
      difficult to predict what's going to happen," Dr Cohen told BBC News
      Online.

      "The reason for doing these studies is that you get the whole
      history. If you learn what happened then, that can inform how you
      deal with [the same problem] in future."

      Dr Cohen added that there are still vast reserves of carbon -
      possibly as much as 14,000 gigatons - locked up as methane ice in
      ocean sediments.

      If global temperatures reach a critical point, it is possible they
      might suddenly be released into the atmosphere causing a similar
      event to the one that occurred during the Jurassic.

      "What we have learned from these rocks is how the Earth can, over a
      long time, combat global warming. What we need to discover now is why
      and at what point it goes into combat mode, and precisely how long
      the conflict takes to resolve," he explained.

      Dr Cohen and his colleagues based their results on studies of mudrock
      rich in organic material and collected near Whitby in North
      Yorkshire.

      Story from BBC NEWS:
      Published: 2004/02/02 15:22:58 GMT
      © BBC

      http://news.bbc.co.uk/2/hi/science/nature/3451787.stm

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