The atmosphere is modeled as graduated concentric spherical shells. The number of shells depends on the path length and altitude range. For example, a path from the ground to 120 km (the top of our model atmospheres) is split into 19 shells: 250 meters thick at the surface, growing to 10 km thick at high altitudes. The temperature and gas concentrations in each shell are taken from the selected model atmosphere. These model data can be viewed/downloaded with the Atmosphere Browser tool. Within each shell, a mass-weighted computation is performed, as described by Gordley and Marshall. Refraction effects are rigorously included in all paths. (Note that radiance spectra for up-looking and downlooking paths are different, whereas transmittance spectra are the same for both directions.) 

DeWitt , could you point me to that "RT program" . I'm at least bookmarking all these references . 

You will see on my http://cosy.com/Science/ColoredBalls.html how it's reasonable to talk about short wavelength versus long , but why to actually calculate temperatures you need the actual full spectra of what ever you are talking about .  Does anyone have a link to the full spectrum of the earth as seen from a distant probe ? How different from that is our averaged surface temperature ?

And does anybody have a full spectrum for Venus ? Not just the lumped albedo with respect to the sun . But as crucially , what is the rest of its spectrum ? What's the long wave portion ?  

One of the first graphs I made when this battle for rationality was heating up back in 2008 is  http://cosy.com/Science/PlanetTempPlotT250.gif , which shows that all the other inner planets follow their gray ball temperature rather closely . ( We are just 9 or 10 degrees ( 3% ) warmer than a flat spectrum ball in our orbit . ) My bet is that that the limped earth's spectrum explains that down to a degree or so .

Using values from NASA's Venus Fact Page , Venus is | 737 % 327.65 |>|  2.25  times hotter than that of an opaque gray ball in its orbit . That means 25.63 time the energy density at its surface as outside . Given that it's Bond albedo is 0.9 , thus it's absorptivity 0.1 , its emissivity in the long wavelength band must be  | 0.1 % 25.63  |>|  0.004  .

Is that everbody's contention ?

A little big of geothermal heating like so many other planets exhibit would sure ease that ratio .