
sorry jc, your link is full of....sophistry.
he states the warm wall is "refer to a hot wall with constant temperature". that means an outside source is controlling the temperature. it is somewhat ridiculous to state later in his calculations that " increasing temperature of the cold wall does not affect the temperature of the independent hot wall".
the second part of the article refers to one of his simplified models-

I am not concerned with his choice of solar input, or the ridiculously foreshortened time to equilibrium BUT it does illustrate an important point which many here dont seem to be able to grasp.
the left half of the graph shows how the object is warming up from solar input. all of the solar input is being used to warm the surface with little energy being released to space. the atmosphere would start to evaporate from the frozen crust on the surface. it would take millions of days or years just to get the atmosphere aloft again, absorbing and retaining most of the solar input. then comes the next big step; warming the ice until it starts to melt. this would take even longer, not just because of the latent heat involved but because by this time a fair amount of the solar input is also being radiated away to space. once the oceans are melted, currents would form to transport heat towards the poles. the amount of energy stored by the atmosphere, oceans, and their currents is totally staggering.
the stored energy in the atmosphere is the source of the 'backradiation'. any atmosphere will return part of its energy to the surface. an atmosphere with greenhouse gases will return more because it is more efficient at absorbing energy from the surface and hence is warmer.
the actual energy returned as 'backradiation' is both highly diffuse and in the low energy IR band of wavelengths. because of this it cannot perform 'work' on the warmer and more highly ordered surface. sunshine is both highly ordered and of a higher energy density wavelength so it can do work on the surface, like increasing the temperature or causing evaporation, etc.
'backradiation' does not 'warm' the surface directly, it passively changes the conditions whereby solar insulation can effect a greater change of temperature with the same amount of energy input. surface temperature is a function of energy input minus energy output. the temperature goes up by either increasing the input or decreasing the output.
****important point****. the energy 'backradiated' by the atmosphere is happening at the same time as the surface is radiating. radiation does not 'cancel out' somewhere between emission and absorption. the net exchange is the combination of gross flows in either direction.

