Re: Global warming problems in homeschool text

From: George Murphy <>
Date: Thu Aug 18 2005 - 10:40:15 EDT

Not quite sure of your point. The fact that there were high CO2 levels in the distant past without fossil fuels certainly doesn't mean that anthropogenic effects can't contribute to high levels today.

  ----- Original Message -----
  From: Glenn Morton
  To: George Murphy ; Sarah Berel-Harrop
  Sent: Thursday, August 18, 2005 10:09 AM
  Subject: Re: Global warming problems in homeschool text

  George Murphy <> wrote:

    There is 1 rather glaring reason for resistance to global warming &
    especially the idea that a major cause of it is use of fossil fuels & other
    human actions: Acceptance of these claims would require some costly actions
    to deal with the problem. I'm not suggesting that all resistance is driven,
    consciously or subconsciously, by economic interests but they certainly are
    a part of the mix.

    GRM: There is another. IN the Cretaceous the level of CO2 in the atmosphere was about 5 times that of today. Life survived it. And It was warmer in the year 800 than it is today. Both of those periods in history lacked cars (to the best of my understanding. At least I don't think dinosaurs were driving hummers)

    Here is some backup data:

      "Several authors have presented evidence that CO2
    and O2 concentrations were elevated throughout the
    Mesozoic. Cerling's (1991) analysis of root paleosols
    found CO2 concentrations from two to ten times that of
    present atmospheric levels (PAL) in the Mesozoic. Carbon
    dioxide concentrations in the low end of this range are
    known to differentially promote plant growth in modern
    plants, but concentration effects in the upper range in
    modern plants or effects of elevated CO2 on plants of
    Mesozoic origin are not complete at this time." Richard
    A. Hengst et al, "Biological Consequences of Mesozoic
    Atmospheres: Respiratory Adaptations and Functional Range
    of Apatosaurus," in Norman Macleod and Gerta Keller,
    "Cretaceous-Tertiary Mass Extinctions: Biotic and
    Environmental Changes (New York: W. W. Norton & Co.,
    1996), p. 328

    When I was born the CO2 content was about 300 on the scale below:

     "Early in late Miocene.-The first evidence of C4 biomass
    being a significant part of local ecosystems in the Old World
    is about 7 to 8 my. Carbonates from preserved paleosols in
    Africa, Asia, and Europe older than 8 my have del 13 C values
    from about -10 to -12 permil. Figure 7 and table 2 show that
    there are compatible with a maximum P(CO2) level of about 700
    ppmV." Thure E. Cerling, "Carbon Dioxide in the Atmosphere:
    Evidence from Cenozoic and Mesozoic Paleosols," American
    Journal of Science, 291(1991):377-400, p. 394
    Miocene Pakistan <700
    Miocene E. Africa <400
    Eocene Wyoming <600
    L. Cretaceous Texas 2500-3300
                   Spain 1600-2600
    U. Triassic/
    l. Jurassic New Haven 2000-3000
                New Haven 2500-4200
                Fundy Rift 3000-6000
    Thure E. Cerling, "Carbon Dioxide in the Atmosphere: Evidence
    from Cenozoic and Mesozoic Paleosols," American Journal of
    Science, 291(1991):377-400, p. 394


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Received on Thu Aug 18 10:42:14 2005

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