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   www.clim-past.net/7/17/2011/   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.