First its great you able to reverse engineer their math.
And I'm nowhere near ready for a full response. I'm a bit awed at the work you put into this and I don't want a hasty response.
But couple of questions, if you don't mind.
1. I didn't see any glaring errors in your Venus absorbtion caluculation of ~80w/m^2.. Have you seen the Pioneer Venus probe data that showed about 200 w/m^2 was getting through the cloud shroud with about 20 w/m^2 getting to the surface? That would seem to imply we are missing 100 w/m^2 somewhere.
2. Have you seen either the ~80w/m^2 absorption number or the 25 degree contribution to warming from CO2 anywhere reputable other than that 1994 paper or its 2002 electronic version?
1. I didn't see any glaring errors in your Venus absorbtion caluculation of ~80w/m^2.. Have you seen the Pioneer Venus probe data that showed about 200 w/m^2 was getting through the cloud shroud with about 20 w/m^2 getting to the surface? That would seem to imply we are missing 100 w/m^2 somewhere.
Have you seen the Pioneer Venus probe data that showed about 200 w/m^2 was getting through the cloud shroud with about 20 w/m^2 getting to the surface?
No my calculation are essential taking the NASA data on albedo and blackbody temp as stated in http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html, for Venus.
The blackbody temp is a function of bond albedo 75% of incident solar flux at Venus orbit reflected before it can get into the atmosphere or the surface to be absorbed and re-emitted as IR to be trapped or absorbed by whatever.
What I have done is calculate a theoretical blackbody calc for change in temperature of a psuedo-mirror above Venus, that reflects solar only at 75%, and transmits 100% venus blackbody IR so we remove the effect of the sulfuric acid cloud layer on surface temperature, but do reduce the solar flux to that which is implied by the listed albedo. The idea being, to isolate that effect that due to a CO2 atmosphere absent all other factors.
The CO2 abosorption is set by the spectrographic absorption qualities of CO2, by the MODTRAN & the Myhre relationship as the MODTRAN program isn't designed to handle 92 bar 96% CO2 atmosphere so I had to make use of both to get where we wanted to be.
What was calculated is a purely theorectical number based on the listed blackbody temp as starting point and a 96.2% CO2, 92 bar atmosphere to establish what the contribution of CO2 to the Venus temperature must be.
An alternative route would be to assume a pure blackbody at 231.7K with a 100% IR absorbing gas in the atmosphere.
The calculation would that be for an absorption of all 163.41 w/m2 instead of the 80 we established for CO2, for which we must compensate by raising temperature to a full:
(163.41*2)/(5.67*10-8)]0.25 = 275.53K
With a delta T of (275.53-231.7) = 43.3oC, still a very long way from the conditions actually found at the surface.
Either way, it becomes clear that the conditions on Venus are not due to IR absorption of the atmosphere alone, however efficient it might be at such.
Rather the temperature conditions on Venus surface must be explained in some other mechanism such as cloud scattering and reflection of IR back to the surface in much the same way that a one way mirror would work which brings us back to the applicablility of the conjecture in comment #31, of R. T. Pierrehumbert and C. Erlick (1998):
AMS Online Journals - On the Scattering Greenhouse Effect of CO2 Ice Clouds Consider an atmosphere-clad planet with net albedo a0 in the solar spectrum. If it is illuminated by a solar flux, S0, and radiates infrared to space at a rate, I0, it is in equilibrium when (1 - a0)S0 = I0. Now introduce a high CO2 ice cloud with albedo ac in the visible and a'c in the infrared, but that absorbs neither solar nor infrared radiation. This perturbs both the solar and infrared terms in the radiation budget, as shown in Fig. 1 . Let the cloud be high enough that it is above virtually all of the infrared-radiating mass of the atmosphere and suppose that the subcloud atmosphere–surface system is a perfect infrared absorber. Taking into account the effects of multiple scattering between the high cloud and the subcloud regions, the cloud changes the planetary solar albedo to
a = ac + a0 [(1 - ac)2/(1 - aca0)]. (1)
If I1 is the upward infrared flux from the subcloud atmosphere, the flux escaping to space is (1 - a'c)I1. To restore equilibrium with the insolation S0, the temperature must change so as to make I1 = [(1 - a)/(1 - a'c)]S0.
The I1 required to balance the absorbed solar radiation becomes infinite if a'c ® 1 with a < 1, in which case the planetary temperature also becomes infinite. In this limit, the cloud acts like a one-way mirror that lets solar radiation in but does not let any planetary radiation out. This state of affairs would violate the second law of thermodynamics, as the planetary temperature would exceed the solar blackbody temperature. In fact, the temperature limits itself because, once the surface warms to solar temperatures, it radiates at solar wavelengths and the albedo for solar and planetary radiation becomes identical. This limit nevertheless shows the potency of the cloud-mirror effect. In contrast, the conventional greenhouse effect for a single-layer IR-absorbing cloud could increase the unperturbed temperature by no more than a factor of 21/4. Unlike the conventional greenhouse effect, the scattering greenhouse effect blocks IR emission to space without the clouds having to absorb any IR themselves. The clouds therefore do not have to heat up in response to the absorbed radiation, which removes a limit to warming inherent in the conventional single-layer case.
2. Have you seen either the ~80w/m^2 absorption number or the 25 degree contribution to warming from CO2 anywhere reputable other than that 1994 paper or its 2002 electronic version?
No, and why would it matter?
The radiative absorption characteristics of CO2 are well known, the blackbody calcs are standard thermodynamics and as we have applied it assumes the maximum efficiency possible for an asbsorption situation. The results are what they are and one is required to look beyond the capacity of CO2 to absorb IR radiation to explain why Venus' surface is as hot as it is.
Just as one must look beyond CO2 alone as to explain all that happens in earth's atmosphere as regards climate here.
2. Have you seen either the ~80w/m^2 absorption number or the 25 degree contribution to warming from CO2 anywhere reputable other than that 1994 paper or its 2002 electronic version?
Remember this one from comment #36?
All that is lack is specific numbers, the requirement that more than IR absorption by CO2 being operative and required is clearly and unequivocally stated.
THE VENUSIAN ENVIRONMENT
3.2 Energy Balance
At a distance of 108.2 million km, Venus is closer to the Sun than the Earth by a factor of about Ö2, and so has about twice the incidence of solar energy. It is also much hotter at the surface, nearly 2 times more than the terrestrial mean of about 300 K. These facts are not simple to reconcile, however, because the ubiquitous and highly reflective cloud cover on Venus reflects 76% of the incoming solar flux and this results in a smaller net solar constant for Venus than for Earth. The high surface temperature must, therefore, be due to ‘greenhouse’ warming produced by the thick, cloudy atmosphere, possibly augmented by a contribution from the internal heat of the planet.
It is not simple to prove that the observed atmospheric conditions can in fact generate such a large ‘greenhouse’ effect. The problem is that the massive amounts of carbon dioxide are very effective at blocking the emission of thermal infrared radiation, but only at those wavelengths where the gas has absorption bands, which are far from covering the entire spectrum. Moderate amounts of water vapour are also required, and even then considerable spectral gaps or ‘windows’ remain. These could be blocked by the clouds, since liquid or solid absorbers present some opacity at every wavelength, the details depending on composition and particle size. The problem for early theorists was that using clouds to ‘close’ the greenhouse also tended to block the incoming sunlight, so that the calculated equilibrium temperature of the surface remained well below that observed.
This problem began to be resolved when it was realised that the clouds are made of sulphuric acid droplets, at least in the higher, most easily measured layers. These have the property of being highly absorbing at thermal infrared wavelengths, while being nearly conservative scatterers in the visible and near infrared. Thus, the clouds tend to diffuse downwards those of the incoming solar photon that they do not reflect to space, while blocking thermal emission from the lower atmosphere and surface. This explains the result, surprising at the time, that the Venera landers in the 1970s were able to photograph the surface in natural light. It also means that radiative transfer models, involving weak as well as strong bands of CO2 and H2O, plus those of the minor constituents CO, HCl and SO2, can account for the high surface temperatures by careful incorporation of the scattering and absorbing properties of the clouds.
The total solar energy diffusing through the cloud cover on Venus corresponds to about 17 watts per cm2 of surface insolation on the average, about 12% of the total absorbed by the planet and the atmosphere. The high opacity of the gaseous atmosphere and cloud at longer wavelengths requires the surface to reach temperatures high enough to melt zinc before the upwelling flux is intense enough, and at shorter wavelengths, so that equilibrium is attained. An airless body with the same albedo and at the same distance from the Sun as Venus would reach equilibrium for a mean surface temperature of only about 230 K. This 500K greenhouse enhancement of the surface temperature compares with only about 30K on Earth and 10K on Mars.