UPDATE: A much better title
In the comments, palindrom points to a toy model which has been submitted to EGU.
Over in the wacky world of Huffington Post, a denialist troll posted a link to this odd paper:John points out the obvious (damn it get to work and post stuff, Eli is gonna retire)
in which Hermann Harde, a laser spectroscopist morphs into a climate modeler, inserts some very good molecular data into what appears to be a rather crude, toy, do-it-yourself planetary atmosphere, and decides the CO2 isn't quite what it's cracked up to be as a greenhouse gas. Can someone who is actually expert at this give an authoritative review of this? (Dammit, Jim), I'm an astronomer, not a planetary atmospheres person, so I don't have the requisite deep knowledge of planetary atmospheres models, but the inquiring minds posting here ought to know ...
Harde calculates a smaller rise in global temperature (about 0.45 C) as a result of doubling CO2, compared with the IPCC number (3C), by a factor of about 7.but we still got a factor of three, so Eli went and read the damn thing. It was actually quite nice, some original stuff in there like
The IPCC result is based on: (1) a rise of 1.2 C from doubled ed CO2 in the atmosphere, causing an enhanced Greenhouse effect, and (2) positive feedbacks (ice-albedo, rising water vapor concentrations) which raise the IPCC estimate to about 3 C +_ 1.5 C.
Harde has calculated only the atmospheric effects, and has ignored feedbacks completely. So his result of 0.45 C should be compared with the IPCC "no-feedback" estimate of 1.2 C. Thus the discrepancy is more like a factor of three, not seven.
The propagation length of the sun light in these layers, which depends on the angle of incidence to the atmosphere and therefore on the geographic latitude, is included by considering the earth as a truncated icosahedron (bucky ball) consisting of 32 surfaces with well defined angles to the incoming radiation and assigning each of the areas to one of the three climate zones.but where the factor of three comes from is easy to see
To identify the influence of the absorbing gases on the climate and particularly the effect of an increasing CO2- concentration on the warming of the earth, a two-layer climate model was developed, which describes the atmosphere and the ground as two layers acting simultaneously as absorbers and Planck radiators. Also heat transfer by convection between these layers and horizontally by winds or oceanic currents between the climate zones is considered. At equilibrium each, the atmosphere as well as the ground, delivers as much power as it sucks up from the sun and the neighbouring layer or climate zone.With this model for each climate zone the temperature progression of the earth and the atmosphere is calculated as a function of the CO2-concentration and several other parameters like ozone and cloud absorption, short- and long-wavelength scattering at clouds as well as the reflection at the earth’s surface.The problem is that there are only two levels. The greenhouse effect is driven by the increase in the height of the atmosphere from which radiation that can be absorbed or emitted by CO2 can reach space. This cannot be captured in a two level model, which, of necessity has to crudely average over a lot of parameters. Of course some of the devil is in the details, such as how much water vapor, clouds, etc is in the second level. The figure, of course, is from Rabett Run's reply to Gerlich and Tschuschner. Harde's stuff is of a much higher quality than the G&T joke.
Oh yes, this appears to be a bad week for climate denialists. Roy Spencer took five on the nose, two from Arthur Smith and three from Barry Bickmore