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Black Soot and Snow: A Warmer Combination

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  • npat1@juno.com
    December 22, 2003 Black Soot and Snow: A Warmer Combination New research from NASA scientists suggests emissions of black soot alter the way sunlight reflects
    Message 1 of 2 , Dec 31, 2003
      December 22, 2003

      Black Soot and Snow: A Warmer Combination
      New research from NASA scientists suggests emissions of black soot alter the way sunlight reflects off snow. According to a computer simulation, black soot may be responsible for 25 percent of observed global warming over the past century.

      Soot in the higher latitudes of the Earth, where ice is more common, absorbs more of the sun�s energy and warmth than an icy, white background. Dark-colored black carbon, or soot, absorbs sunlight, while lighter colored ice reflects sunlight.

      Soot in areas with snow and ice may play an important role in climate change. Also, if snow- and ice-covered areas begin melting, the warming effect increases, as the soot becomes more concentrated on the snow surface. �This provides a positive feedback (i.e. warming); as glaciers and ice sheets melt, they tend to get even dirtier,� said Dr. James Hansen, a researcher at NASA�s Goddard Institute for Space Studies, New York.

      Hansen and Larissa Nazarenko, both of the Goddard Institute and Columbia University�s Earth Institute, found soot�s effect on snow albedo (solar energy reflected back to space), which has been neglected in previous studies, may be contributing to trends toward early springs in the Northern Hemisphere, thinning Arctic sea ice, melting glaciers and permafrost. Soot also is believed to play a role in changes in the atmosphere above the oceans and land.

      �Black carbon reduces the amount of energy reflected by snow back into space, thus heating the snow surface more than if there were no black carbon,� Hansen said.

      Soot�s increased absorption of solar energy is especially effective in warming the world�s climate. �This forcing is unusually effective, causing twice as much global warming as a carbon-dioxide forcing of the same magnitude,� Hansen noted.

      Hansen cautioned, although the role of soot in altering global climate is substantial, it does not alter the fact greenhouse gases are the primary cause of climate warming during the past century. Such gases are expected to be the largest climate forcing for the rest of this century.

      The researchers found that observed warming in the Northern Hemisphere was large in the winter and spring at middle and high latitudes. These observations were consistent with the researchers� climate model simulations, which showed some of the largest warming effects occurred when there was heavy snow cover and sufficient sunlight.

      Hansen and Nazarenko used a leading worldwide-climate computer model to simulate effects of greenhouse gases and other factors on world climate. The model incorporated data from NASA spacecraft that monitor the Earth�s surface, vegetation, oceans and atmospheric qualities. The calculated global warming from soot in snow and ice, by itself in an 1880-2000 simulation, accounted for 25 percent of observed global warming. NASA�s Terra and Aqua satellites are observing snow cover and reflectivity at multiple wavelengths, which allows quantitative monitoring of changing snow cover and effects of soot on snow.

      The research is in the paper �Soot Climate Forcing via Snow and Ice Albedos,� appearing online this week in the Proceedings of the National Academy of Sciences.

      This research was funded by NASA�s Earth Science Enterprise. The Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth system science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.

      For more information and images on the Internet, visit:
      http://www.gsfc.nasa.gov/topstory/2003/1223blacksoot.html

      A previous, related NASA release, �NASA Finds Soot Has Impact on Global Climate,� is at:
      http://www.gsfc.nasa.gov/topstory/2003/0509pollution.html

      ###
      Contacts:

      David E. Steitz
      Headquarters, Washington
      Phone: 202/358-1730

      Rob Gutro/Krishna Ramanujan
      Goddard Space Flight Center, Greenbelt, Md.
      Phone: 301/286-4044; 607/273-2561

      Mary Tobin
      Columbia University, New York
      Phone: 845/365-8607




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    • Mike Neuman
      The key conclusion of the study is this: Although the role of soot in altering global climate is substantial, it does not alter the fact greenhouse gases are
      Message 2 of 2 , Dec 31, 2003
        The key conclusion of the study is this: "Although the role of soot
        in altering global climate is substantial, it does not alter the fact
        greenhouse gases are the primary cause of climate warming during the
        past century. Such gases are expected to be the largest climate
        forcing for the rest of this century."

        --- In ClimateArchive@yahoogroups.com, npat1@j... wrote:
        > December 22, 2003
        >
        > Black Soot and Snow: A Warmer Combination
        > New research from NASA scientists suggests emissions of black soot
        alter the way sunlight reflects off snow. According to a computer
        simulation, black soot may be responsible for 25 percent of observed
        global warming over the past century.
        >
        > Soot in the higher latitudes of the Earth, where ice is more
        common, absorbs more of the sun's energy and warmth than an icy,
        white background. Dark-colored black carbon, or soot, absorbs
        sunlight, while lighter colored ice reflects sunlight.
        >
        > Soot in areas with snow and ice may play an important role in
        climate change. Also, if snow- and ice-covered areas begin melting,
        the warming effect increases, as the soot becomes more concentrated
        on the snow surface. "This provides a positive feedback (i.e.
        warming); as glaciers and ice sheets melt, they tend to get even
        dirtier," said Dr. James Hansen, a researcher at NASA's Goddard
        Institute for Space Studies, New York.
        >
        > Hansen and Larissa Nazarenko, both of the Goddard Institute and
        Columbia University's Earth Institute, found soot's effect on snow
        albedo (solar energy reflected back to space), which has been
        neglected in previous studies, may be contributing to trends toward
        early springs in the Northern Hemisphere, thinning Arctic sea ice,
        melting glaciers and permafrost. Soot also is believed to play a role
        in changes in the atmosphere above the oceans and land.
        >
        > "Black carbon reduces the amount of energy reflected by snow back
        into space, thus heating the snow surface more than if there were no
        black carbon," Hansen said.
        >
        > Soot's increased absorption of solar energy is especially effective
        in warming the world's climate. "This forcing is unusually effective,
        causing twice as much global warming as a carbon-dioxide forcing of
        the same magnitude," Hansen noted.
        >
        > Hansen cautioned, although the role of soot in altering global
        climate is substantial, it does not alter the fact greenhouse gases
        are the primary cause of climate warming during the past century.
        Such gases are expected to be the largest climate forcing for the
        rest of this century.
        >
        > The researchers found that observed warming in the Northern
        Hemisphere was large in the winter and spring at middle and high
        latitudes. These observations were consistent with the researchers'
        climate model simulations, which showed some of the largest warming
        effects occurred when there was heavy snow cover and sufficient
        sunlight.
        >
        > Hansen and Nazarenko used a leading worldwide-climate computer
        model to simulate effects of greenhouse gases and other factors on
        world climate. The model incorporated data from NASA spacecraft that
        monitor the Earth's surface, vegetation, oceans and atmospheric
        qualities. The calculated global warming from soot in snow and ice,
        by itself in an 1880-2000 simulation, accounted for 25 percent of
        observed global warming. NASA's Terra and Aqua satellites are
        observing snow cover and reflectivity at multiple wavelengths, which
        allows quantitative monitoring of changing snow cover and effects of
        soot on snow.
        >
        > The research is in the paper "Soot Climate Forcing via Snow and Ice
        Albedos," appearing online this week in the Proceedings of the
        National Academy of Sciences.
        >
        > This research was funded by NASA's Earth Science Enterprise. The
        Enterprise is dedicated to understanding the Earth as an integrated
        system and applying Earth system science to improve prediction of
        climate, weather and natural hazards using the unique vantage point
        of space.
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