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Sea level may rise more than 1m by 2100

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  • Mike Neuman
    Sea level may rise more than 1m by 2100 Julio Godoy | Berlin, Germany 31 December 2006 06:00 Ocean levels will rise faster than expected if greenhouse-gas
    Message 1 of 1 , Jan 2, 2007
      Sea level may rise more than 1m by 2100
      Julio Godoy | Berlin, Germany
      31 December 2006 06:00

      Ocean levels will rise faster than expected if greenhouse-gas
      emissions continue to rise, a leading German researcher warns.

      Using Nasa data, Stefan Rahmstorf, professor of physics of the oceans
      at the University of Potsdam near Berlin, estimates that the sea
      level could rise by 140cm by 2100.

      Rahmstorf, a member of the German Advisory Council on Global Change,
      is considered a leading European researcher on global warming and its
      effect on oceans.

      "The semi-empirical model we used to process Nasa data showed a
      proportional constant sea level rise of 3,4mm per year per degree
      Celsius," Rahmstorf said. "Then we applied this constant
      proportionality to future earth-surface warming scenarios of the
      Intergovernmental Panel on Climate Change [IPPC], and came to
      estimate that by the year 2100, sea level could rise between 50cm and
      140cm above the level measured in 1990."

      Through the 20th century, global warming led to an average 20cm rise
      in sea level. But most computer models of climate change used at
      present significantly underestimate sea-level rise, Rahmstorf
      said. "Future projections of sea level based on these climate models
      are therefore unreliable."

      Currently, sea level is rising at 3cm per decade, faster than
      projected in the scenarios of the IPCC third assessment report,
      Rahmstorf added.

      The IPCC, an intergovernmental team of scientists carrying out a wide
      range of research related to climate change, was established in 1988
      by the World Meteorological Organisation and the United Nations
      Environmental Programme. It aims to assess scientific, technical and
      socio-economic information relevant for understanding of climate
      change, its potential impact and options for adaptation and

      Carbon dioxide
      Scientific research has found that industrial activities have
      produced greenhouse-gas emissions considerably higher than levels
      observed before the industrial revolution.

      Concentration of carbon dioxide, the most potent of greenhouse gases,
      has risen from about 280 parts per million (ppm) in the atmosphere in
      the year 1750 to about 380 ppm today.

      This rise is primarily due to the burning of fossil fuels and, to a
      lesser extent, deforestation. Scientists estimate that if the present
      emissions trend continues, the atmosphere could heat up by about five
      degrees Celsius by 2100.

      Studies by the Potsdam Institute for Climate Impact Research suggest
      that this would roughly be the temperature difference between an ice
      age and a warm stage. But while the rise of average temperatures by
      about five degrees between the last great ice age and today took 5
      000 years, the new global warming would need only 100 years.

      Rahmstorf acknowledged that forecasts of global warming and its
      effects on sea levels continue to be marked by uncertainty. "The fact
      that we get such different estimates using different methods shows
      how uncertain our sea level forecasts still are," Rahmstorf said.

      Ice sheets
      A major reason for the uncertainty is the behaviour of the large ice
      sheets in Greenland and Antarctica.

      A likely consequence of a massive melting of the ice masses on the
      North Pole could be the breakdown of the North Atlantic Current. The
      current is the northern extension of the Gulf Stream, and constitutes
      a warm-water current flowing between Britain and Iceland. This has
      considerable effect in moderating the north European and Scandinavian

      "One critical factor for the continuation of this current is the
      amount of fresh water that enters the northern Atlantic region in the
      future," Rahmstorf said. "This will depend in large part on the speed
      at which Greenland's ice sheet melts."

      Rahmstorf, who earlier this year co-authored a research paper titled
      The Future Oceans: Warming Up, Rising High, Turning Sour, said
      reliable prediction on the risk of a total stoppage of deepwater
      formation in the northern Atlantic is not possible given present

      But he pointed out that experts have evaluated that risk at more than
      50% if global warming is between three and five degrees Celsius.

      Rahmstorf said greenhouse-gases emissions are also increasing the
      acidity of oceans. "In the atmosphere, carbon dioxide does not react
      with other gases, but in the ocean it dissolves, contributing to the
      acidification of seawater," he said. This acidity is a serious threat
      to marine biodiversity.

      "There is a good chance to avoid such dangerous climate change if
      global warming caused by human activities is limited to two degrees
      in the coming decades," Rahmstorf said. -- IPS
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