Of course nature doesn’t work that way. The impact of the increase in CO2 at the radiant layer is pretty accurate. The location of that radiant layer is not all that accurate. Energy from that layer will not be felt fully at the surface since you cannot transfer energy without some loss. Under ideal conditions, the radiant layer energy would increase by 3.7 Wm-2 (1.5C) and depending on the conditions between the surface and that layer, the surface temperature would increase by 1 to 1.2 degrees “if all things remain equal”. To go beyond that 1 to 1.2 would require some positive feed back to the CO2 forcing. Water vapor itself is a negative feed back, contrary to popular opinion. Since water vapor shares parts of the CO2 spectrum, it would absorb some of the energy at the radiant layer which would increase the rate of convection and since water vapor does not share all of the CO2 spectrum, provide a radiant path through the atmospheric window, decreasing the CO2 impact. That was the 20Wm-2 the K&T missed.
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