I think it is quite unfair to Max Planck to suggest that his quantum theory of radiation
in any way justifies the concept of a Greenhouse Effect by which “back radiation” from the atmosphere can somehow warm the Earth.
Planck was the editor of the Journal that first published Einstein’s seminal papers. It was Planck’s Journal, and there was only one “peer reviewer”, Max Planck himself. Einstein was able to derive the Planck distribution law from first principles only if he postulated the existence of something he called “negative absorption” which we now call stimulated emission which is the basis for all our lasers. Actually, Tolman who referred to Einstein’s paper, was actually the first to suggest that the phenomenon of negative absorption could be used in such a way as to reinforce a primary beam: thus anticipating lasers as early as the 1930’s
One of Planck’s friends and colleagues, Fritz Haber, who had been director of the Kaiser Wilhelm Institute for Physical Chemistry, had been force to resign because of his “Jewish Heritage”. On the first anniversary of his death, Planck and others were courageous enough to arranged for a memorial service for him. They got permission from the Nazis to hold it provided no media publicity appeared about it.
Planck presided over it, starting the proceedings with the perfunctory “Heil Hitler” salute. Those who knew Haber memorialized him for his service to the “fatherland”: his invention of the “Haber Process” for producing ammonia directly from nitrogen and hydrogen. The process allowed Germany to continue producing explosives during WW I despite the Allied blockade. He was also praised for being the head of the German Chemical Warfare Group. He had developed chemical warfare agents and had supervised the use of poison gas on the battlefield. He didn’t live to see some of his inventions used to exterminate some of his relatives, or even he himself had he lived longer!
On the same day, another memorial service was held for Haber in Palestine: at the Chaim Weitzmann Institute. He was memorialized in Hebrew for his service to mankind in developing the process that allowed the plentiful production of artificial fertilizers. I once read that there is a statue of him somewhere in Germany with the inscription “Der der hat brot aus luft gemacht” - “he who made bread from air”.
Now, consider the following thought experiment. Two black bodies are lined up face to face with their apertures adjacent to each other. Both are perfectly insulated from their surroundings (except for their open apertures).
And is always from the hotter black body to the colder black body as required by the Second Law of Thermodynamics.
Is there any meaning or physical effect associated with the “backwelling” of radiation from the colder blackbody to the warmer one. It has some effect on the overall balance but cannot change the direction of energy flow even as they eventually equilibrate to the same temperature.
Consider a 10 Newton force operating from left to right on a I Kg mass on a frictionless air table. At the same time a 2 Newton force operates on the mass from right to left. Now you can calculate what the acceleration and motion to the left would be from the 2 Newton force if it were operating by itself. The calculation would be meaningless since the real motion is to the right under the net force of 8 Newtons.
Now Spencer would argue that the back radiation from the colder body actually impedes the cooling of the hotter body.
But the atmosphere is not a solid body, and whatever absorbance it has for IR ground radiation is immediately transformed into emittance of that radiation from the atmosphere to the much colder free space. In the atmospheric window for IR radiation from the Earth, the cooling is a one-step process: photons going directly from the Earth surface to free space. In the gas absorption bands, it is a two step process: from the Earth’s surface to the atmosphere to free space. I think the overall cooling effect is not significantly different.
I once had a discussion with someone who used the Spencer argument and claimed that the cooling was “delayed” by the two-step process. I then asked him if he could tell me by how much it was “delayed”: was it delayed by a microsecond, a millisecond, a second, an hour, or a day? I never got a response.