Time for water vapor to generate more greenhouse effect than latent heat? I have an argument with a climate change denier.
He says the rise of water vapor in the atmosphere causes a &quot;much larger&quot; cooling effect by taking vaporisation heat from the ground than the heat generated by the additional greenhouse effet.
I say the additional greenhouse effect integrates with time, so after a certain time T (which I suspect &quot;small&quot;), this heat will compensate the latent heat taken from the ground.
Does anyone have a reference establishing the order of magnitude of T ?
Note the question is NOT about the &quot;normal&quot; water cycle where latent heat is taken at vaporisation and released at condensation, it is about the (undisputed) global augmentation of water vapor in the troposphere.
I am doing some calculations on this question myself. The atmospheric lapse rate is about 6.5K/1.000m. The adiabatic lapse rate is 9.8K/1.000 and the dry lapse rate of the naturally unstable atmosphere of Earth should even be 10.8K. So arguably the constant transport of latent heat by vapor from the surface into the atmosphere is reducing the lapse rate by some 4.3K/1.000m. Without a doubt the GHE would be much larger if it was not for the latent heat provided by vapor.
The GHE itself is a function of the emission temperature, which again is a function of the emission altitude. Vapor increases this emission altitude, which is why it is considered a GHG, the most significant one actually.
We need to ask what size GHE has (not 33K, but less), what bigger size it counterfactually had without latent heat and a lapse rate of 10.8K, determine the share of vapor in this case, and compare it to the (negative) effect of latent heat. Depending on what is bigger, vapor is either a GHG or an anti-GHG. From all the modelling so far I get definitely the latter result.