Mark Twain observed, “The trouble with most of us is that we know too much that ain't so.”
Adding to the “Δ33C without an atmosphere” (see other article) that completely ain’t so is the example of Venus.
Venus, we are told, has an atmosphere that is almost pure carbon dioxide and an extremely high surface temperature, 750 K, and this is allegedly due to the radiative greenhouse effect, RGHE. But the only apparent defense is, “Well, WHAT else could it BE?!”
Well, what follows is the else it could be. (Q = U * A * ΔT)
Venus is half the distance to the sun so its average solar constant/irradiance is twice as intense as that of earth, 2,615 W/m^2 as opposed to 1,368 W/m^2.
But the albedo of Venus is 0.77 compared to 0.31 for the Earth - or - Venus 601.5 W/m^2 net ASR (absorbed solar radiation) compared to Earth 943.9 W/m^2 net ASR.
The Venusian atmosphere is 250 km thick as opposed to Earth’s at 100 km. Picture how hot you would get stacking 2.5 more blankets on your bed. RGHE’s got jack to do with it, it’s all Q = U * A * ΔT.
The thermal conductivity of carbon dioxide is about half that of air, 0.0146 W/m-K as opposed to 0.0240 W/m-K so it takes twice the ΔT/m to move the same kJ from surface to ToA.
Put the higher irradiance & albedo (lower Q = lower ΔT), thickness (greater thickness increases ΔT) and conductivity (lower conductivity raises ΔT) all together: 601.5/943.9 * 250/100 * 0.0240/0.0146 = 2.61.
So, Q = U * A * ΔT suggests that the Venusian ΔT would be 2.61 times greater than that of Earth. If the surface of the Earth is 15C/288K and ToA is effectively 0K then Earth ΔT = 288K. Venus ΔT would be 2.61 * 288 K = 748.8 K surface temperature. All explained, no need for any S-B BB RGHE hocus pocus.
Simplest explanation for the observation.