This is something I wrote about long ago (reference pg. 16), but in a recent Slayer email exchange I re-realized just how important it was. Hopefully any Slayers will follow up in the comments if anything else needs to be added.
In Misunderstood Basic Concepts and the Greenhouse Effect, it is stated:
“The tropospheric temperature lapse rate would not exist without the greenhouse effect. While it is true that convective overturning of the atmosphere leads to the observed lapse rate, that convection itself would not exist without the greenhouse effect constantly destabilizing the lapse rate through warming the lower atmosphere and cooling the upper atmosphere.”
However, let us look once again at the derivation for the lapse rate (also reference this previous post):
When there is no longer any gain or loss of energy in a column of gas (i.e., when it is in energy equilibrium), then the energy ‘U’ of an arbitrary parcel of gas is given by the sum of its thermal and gravitational potential energies. The sum of thermal and gravitational potential energies is:
U = mCpT + mgh
However, this energy is constant since there is no other energy input (or loss), and so its differential is equal to zero:
dU = 0 = mCp*dT + mg*dh
which results in
dT/dh = -g/Cp
Note that this equation and its derivation has no reference to greenhouse gases or thermal radiation at all – the lapse rate is dependent only upon the gas’ thermal capacity, and the strength of gravity, and this will occur for any gas even if it is totally “radiatively inert”, and, even if the gas isn’t undergoing bulk convection; the lapse rate develops at the infinitesimal scale of the action of gravity on the particles of the gas.
Now I will simply quote my reference, with some editing:
This result is independent of any effect of greenhouse gases (GHG’s) as no consideration of those were made in the derivation.
Now, it is expected that GHG’s increase the temperature of the bottom of the atmosphere, while decreasing that at the top, and so this would require that the lapse rate of temperature to be larger than what was derived by means without reference to GHG’s.
That is, the lapse rate should be steeper than -g/Cp = -10 K/km because there is (ostensibly) already a GHE in operation in the atmosphere.
Yet this is clearly not the case because the fastest lapse rate derived and observed in meteorology is still that value as can be derived from -g/Cp, independent of any preexisting GHE.
Additionally, if we examine the effect of the strongest GHG on the lapse rate, which is water vapour, we find that it acts to reduce the lapse rate, not increase it, which is again in direct opposition to the requirements of the GHE postulate.
There is not any room for the postulate of a radiative GHE because observations from the real world, and mathematics, refute it.
The fact that the dry lapse rate of the atmosphere is -10 K/km, and not steeper, is a 100% refutation of the postulate of a radiative greenhouse effect.
The radiative greenhouse effect is predicated upon the requirement that it “destabiliz[es] the lapse rate through warming the lower atmosphere and cooling the upper atmosphere”.
That means that the greenhouse effect has to make the temperature gradient of the atmosphere to be greater than the lapse rate that is achieved by -g/Cp! Yet, the lapse rate is not steeper than this, and, when the strongest greenhouse gas is present, the opposite occurs!