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CO2 today and 20 million years ago

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  • npat1@juno.com
    Carbon Dioxide (CO2). In nature, carbon is cycled between various atmospheric, oceanic, land biotic, marine biotic, and mineral reservoirs. The largest
    Message 1 of 1 , Feb 11, 2003
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      "Carbon Dioxide (CO2). In nature, carbon is cycled between various
      atmospheric, oceanic, land biotic, marine biotic, and mineral reservoirs.
      The largest fluxs occur between the atmosphere and surface water of the
      oceans. In the atmosphere, carbon predominantly exists in its oxidized
      form as CO2. Atmospheric carbon dioxide is part of this
      global carbon cycle, and therefore its fate is a complex function of
      geochemical and biological processes. Carbon dioxide concentrations in
      the atmosphere increased from approximately 280 parts per million by
      volume (ppmv) in preindustrial times to 367 in 1999, a 31 percent
      increase (IPCC 2001). The IPCC notes that:

      "[t]his concentration has not been exceeded during the
      past 420,000 years, and likely not during the past 20
      million years. The rate or increase over the past century
      is unprecedented, at least over the past 20,000 years."

      The IPCC definitively states that "the present atmospheric CO2 increase
      is caused by anthropogenic emissions of CO2" (IPCC 2001). Forest
      clearing, other biomass burning, and some non-energy production processes
      (e.g., cement production) also emit notable quantities of carbon dioxide.

      In its second assessment, the IPCC also stated that "[t]he increased
      amount of carbon dioxide [in the atmosphere] is leading to climate change
      and will produce, on average, a global warming of the Earth's
      surface--although the magnitude and significance of the effects are not
      fully resolved" (IPCC 1996).

      Excerpt from Inventory of U.S. Gas Emissions and Sinks 1990-2000
      http://yosemite.epa.gov/oar/globalwarming.nsf/UniqueKeyLookup/SHSU5BUM9T/
      $File/ghg_gwp.pdf

      From what I now know about the Paleocene-Eocene Thermal Maximum (PETM) of
      55 Ma and the Eocene, 20 Ma seems about right for the time that the
      concentration of CO2 was as high as it is today (and increasing ! ).

      Pat


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