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I know someone who disputes the idea that the Earth's atmospheric temperature would average -18 deg C in the absence of greenhouse gasses. He maintains that conductive heating would warm the air and convective transport mix it, and, since the gasses are not greenhouse gasses they would not lose the heat by radiating it away, and so the heat could build up.

The thought experiment runs thus: a planet in earth's orbit without water and an atomosphere of, say, oxygen and nitrogen.

It seems to me that being such a small percentage (15%) of the incident radiation striking the Earth (even if, in the absence of GHG, the incident radiation would be higher) the effect could not possibly build up because the conduction would work the other way at night and most of it would, in turn be radiated away into space.

In short, he is saying that a significant portion of the effective warming we see in the atmosphere is attributable to this effect, making the basis for calculating the greenhouse gas effect suspect.

I don't have the mathematics to estimate this effect on balance, and it seems to me that it must have been accounted for previously, but I do not know. I would particularly appreciate a reference to a paper or article that discusses this aspect of atmospheric warming.

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  • $\begingroup$ The premise is wrong. What the meaning of considering soil to atmosphere heat transfer? Beside accurate modelling heat which dominates the balance is from sun. Greenhouse gas store that. Non greenhouse don't. Far away to modelling climate but the assertion " since the gasses are not greenhouse gasses they would not lose the heat by radiating it away, and so .." does not make any sense. $\endgroup$ – Alchimista Jan 6 at 9:03
  • $\begingroup$ @Alchimista, Are you saying that non-GHGasses DO lose energy by radiant heat? By what mechanism? Over what wavelengths? And if they emit it, why would they not also absorb and therefore scatter it by the same mechanisms, thus allowing some heat retention in the atmosphere? (The mechanisms by which GHG molecules absorb and re-emit IR are well understood.) Can you provide me with numbers or evidence to show that? I'd greatly appreciate it. Thank you. $\endgroup$ – Roger Neyman Jan 6 at 19:05
  • $\begingroup$ @Alchemista, continued. Absent GHGasses solar radiation would heat our hypothetical planet's surface a bit more than Earth's. Most of that heat, it is true, would be re-radiated in longer wavelength IR which would pass through the atmosphere back in to space. A very small portion of the energy would be conducted to the air within a few centimeters of the surface, to be distributed by convective mixing. The "meaning" of considering this portion is obviously to calculate what accumulative effect such warming (balanced by the cooling of the air by the same means at nighttime) would have. $\endgroup$ – Roger Neyman Jan 6 at 19:11
  • $\begingroup$ I do not mot any number not modelling the physics of the atmosphere. Greenhouse gas are necessary for the atmosphere that we actually have. If you remove them T will be in due time lower. I mostly pointed to the fact that non GH gas radiates heat as everything else. The point is that GH absorb heat and re emit it partially back. Non GH can get heat by contact but they are already doing it.. And surely they radiate to the vacuum of space up where they can. $\endgroup$ – Alchimista Jan 6 at 20:48
  • $\begingroup$ You don't need fine details to contrast a wrong assumption. $\endgroup$ – Alchimista Jan 6 at 20:49

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