Monday, January 10, 2011

Climate Models Differ on CO2 Warming Effect by over 32°F

A paper published today in the journal Climate of the Past illustrates the magnitude of confusion in climate science regarding the 'settled' 'basic physics' of the CO2 'greenhouse effect.' The climate model results of this paper are compared to 2 other recent peer-reviewed papers and show that the 3 climate models differ by over 32 degrees F (18.3°C) in explaining the 'greenhouse warming' effect of CO2 during the period of time when the entire Earth was covered by ice (the "snowball Earth"). This huge difference dwarfs the IPCC-claimed computer-modeled 0.6°C of anthropogenic global warming during the industrial age and the IPCC-claimed 3°C global warming prediction for doubled CO2 concentrations derived from the same family of computer models. As this study gingerly points out, these are "large differences" between climate models, resulting from differing "assumptions" of the "model physics," in other words, due to whatever fudge factors one chooses to plug in for the 'greenhouse effect' of CO2. All claims of catastrophic anthropogenic global warming rest upon the shaky scientific foundations and gross assumptions of these same climate models.

Three climate models compared for global temperature claimed to result from 0.2 bar CO2 atmospheric level:

1. Hu et al finds 268K = -5.15C = 22.73F
2. Pierrehumbert et al finds 255K = -18.15C = -.67F
3. Le Hir et al finds (for 50% less CO2 or 0.1 bar) 270K+3K (temp increase claimed for doubled CO2 per IPCC) = 273K = -.15C = 31.73F

Final Revised Paper (PDF, 470 KB)

Clim. Past, 7, 17-25, 2011   doi:10.5194/cp-7-17-2011

Model-dependence of the CO2 threshold for melting the hard Snowball Earth

Y. Hu, J. Yang, F. Ding, and W. R. Peltier

Abstract. One of the critical issues of the Snowball Earth hypothesis is the CO2 threshold for triggering the deglaciation. Using Community Atmospheric Model version 3.0 (CAM3), we study the problem for the CO2 threshold. Our simulations show large differences from previous results (e.g. Pierrehumbert, 2004, 2005; Le Hir et al., 2007). At 0.2 bars of CO2, the January maximum near-surface temperature is about 268 K, about 13 K higher than that in Pierrehumbert (2004, 2005), but lower than the value of 270 K for 0.1 bar of CO2 in Le Hir et al. (2007). It is found that the difference of simulation results is mainly due to model sensitivity of greenhouse effect and longwave cloud forcing to increasing CO2 [in other words the 'basic physics' of the CO2 'greenhouse effect']. At 0.2 bars of CO2, CAM3 yields 117 Wm−2 of clear-sky greenhouse effect and 32 Wm−2 of longwave cloud forcing, versus only about 77 Wm−2 and 10.5 Wm−2 in Pierrehumbert (2004, 2005), respectively. CAM3 has comparable clear-sky greenhouse effect to that in Le Hir et al. (2007), but lower longwave cloud forcing. CAM3 also produces much stronger Hadley cells than that in Pierrehumbert (2005).

Effects of pressure broadening and collision-induced absorption are also studied using a radiative-convective model and CAM3. Both effects substantially increase surface temperature and thus lower the CO2 threshold. The radiative-convective model yields a CO2 threshold of about 0.21 bars with surface albedo of 0.663. Without considering the effects of pressure broadening and collision-induced absorption, CAM3 yields an approximate CO2 threshold of about 1.0 bar for surface albedo of about 0.6. However, the threshold is lowered to 0.38 bars as both effects are considered.


  1. "One of the critical issues of the Snowball Earth hypothesis is the CO2 threshold for triggering the deglaciation."

    The fact that CO2 lags temperature by app. 800 years in the Vostok records renders this premise rather absurd, does it not?

  2. The warmist religion continues to insist that CO2 is The climate control knob, no matter how much contrary evidence is presented, including the Vostok and Greenland ice cores. Scientists can only get grant funding by proposing research to try to "prove" the CO2 control knob theory; anything contrary is left unproposed and unfunded.

  3. Howard Hayden has made the point rather succinctly that if this were science , there would be one model accurately explaining global temperature rather than 30 giving widely divergent numbers .

    I keep challenging the "climate science" community to show me the handful of equations proving they even know how to compute the temperature of a simple radiantly heated colored ball .

    Marty Hertzberg is about the only voice I have seen pointing out that the appropriate "null hypothesis" is a gray ( flat spectrum ) ball in our orbit which gives a temperature of about 279k or 4c . Significantly , this is above 0c .

    Instead , both sides of the debate , for some reason I'd love to know the history of , use an assumption that we absorb heat from the sun with an observed coefficient of about 0.7 , but , slightly impossibly , radiate as a black body with a coefficient of 1.0 . I have never seen anybody show the calculation for an actual spectrum . Most particularly , if there is any "tipping point" around , it is "snowball earth" , and I have never seen a computation proving that snow's spectrum is so peaked in the 300k region that it pulls the mean temperature below 0c .

    I continue to find the understanding of the most fundamental classical physics evident in the field , pathetic , and what it says about the teaching of hard science now days , frightening .

  4. yes, not to mention the silly assumption that ideal gases behave as solid blackbodies

  5. Are you planning on updating the graph at the top of your blog with up to date data?

    Or wouldn't that fit your agenda?

  6. cthulhu,
    oh my gosh, the global temperature has increased an average 0.00363152C per year over the past 13 years! At this rate, by 2100 the globe will be 0.3C hotter!!! BUY YOUR LIFEBOAT NOW! and DON'T look at Hansen's computer model predictions in 1988 and 1998 of where the global warming - sorry climate change - was "supposed" to be by now, since that wouldn't fit your agenda nor your delusions.

    BTW the header graph will be updated annually in February- the latest monthly data has always been located right over there ->

    #Data processed by
    #Please check original source for first-hand data and information:
    #Data from Remote Sensing Systems
    #File: RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_2.txt
    #Time series (rss) from 1979 to 2011
    #Selected data from 1998
    #Least squares trend line; slope = 0.00363152 per year
    1998 0.263463
    2011 0.310673
    #Data ends
    #Number of samples: 2
    #Mean: 0.287068

  7. I agree with Bob Armstrong above.
    Its not hard to show (making no assumptions about the nature of the planet) that the average radiative temperature is about 279K.(6C).
    A calculation based on the Suns radiative output received at the Earths orbit gives this undramatic result.

    How the IPCC proponents turn CO2 induced AGW into a 33K greenhouse gain is a smart piece of creative accounting.
    Most of the values are calculated assuming perfect Black body emitters.
    Very few of the figures used are measured by experiment.
    Given the wide scope for fiddling the result its note surprising that several values are produced for the same quantity

  8. And how do they explain the continental cooling that has occurred in the U.S. since 1998?