Guest Post by Willis Eschenbach

On an average day you’ll find lots of people, including NASA folks like Gavin Schmidt and James Hansen, evaluating how well the climate models compare to reality. As I showed here, models often don’t do well when matched up with real-world observations. However, they are still held up as being accurate by the IPCC, which uses climate models throughout their report despite their lack of rigorous testing.

XKCD, of course.

But if you ask me, that evaluation of the models by comparing them with reality is not possible. I think that the current uncertainties in the total solar irradiation (TSI) and aerosol forcings are so large that it is useless to compare climate model results with observed global temperature changes.

Why do I make the unsubstantiated claim that the current uncertainties in TSI and aerosols are that large? And even if they are that large, why do I make the even more outlandish claim, that the size of the uncertainties precludes model testing by comparison with global temperature observations?

Well … actually, I’m not the one who made that claim. It was the boffins at NASA, in particular the good folks at GISS, including James Hansen et al., who said so (emphasis mine) …

Total solar irradiance (TSl) is the dominant driver of global climate, whereas both natural and anthropogenic aerosols are climatically important constituents of the atmosphere also affecting global temperature. Although the climate effects of solar variability and aerosols are believed to be nearly comparable to those of the greenhouse gases (GHGs; such as carbon dioxide and methane), they remain poorly quantified and may represent the largest uncertainty regarding climate change. … The analysis by Hansen et al. (2005), as well as other recent studies (see, e.g., the reviews by Ramaswamy et al. 2001; Kopp et al. 2()05b; Lean et al. 2005; Loeb and Manalo-Smith 2005; Lohmann and Feichter 2005; Pilewskie et al. 2005; Bates et al. 2006; Penner et al. 2006), indicates that the current uncertainties in the TSI and aerosol forcings are so large that they preclude meaningful climate model evaluation by comparison with observed global temperature change. These uncertainties must be reduced significantly for uncertainty in climate sensitivity to be adequately constrained (Schwartz 2004).

“Preclude meaningful climate model evaluation” … hmmm. Of course, they don’t make that admission all the time. They only say things like that when they want to get money for a new satellite. The rest of the time, they claim that their models are accurate to the nearest 0.15°C …

Now, the satellite that the NASA GISS folks (very reasonably) wanted to get money for, the very satellite that the aforementioned study was written to promote, was the Glory Mission … which was one of NASA’s more unfortunate failures.

NASA’s Glory Satellite Fails To Reach Orbit WASHINGTON — NASA’s Glory mission launched from Vandenberg Air Force Base in California Friday at 5:09:45 a.m. EST failed to reach orbit. Telemetry indicated the fairing, the protective shell atop the Taurus XL rocket, did not separate as expected about three minutes after launch.

So … does this mean that the evaluation of models by comparison with observed global temperature change is precluded until we get another Glory satellite?

Just askin’ … but it does make it clear that at this point the models are not suitable for use as the basis for billion dollar decisions.

w.

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