Yes, I am here.  I signed up the other day to answer this and a couple other topics that caught my eye.

i am having the same trouble with lost posts.  This is the second attempt at this post.

It is an interesting question and one that is difficult to answer with clarity.  Not because the physics is uncertain but because the described process involves so many sub-processes that the effects become obscured in the minutia.

Let me try.  I suspect you know this theory but I will explain anyway to be sure you and I agree (it is entirely possible that I am wrong).

First off internal energy (measured by temperature) is released in the form of radiation of frequency that is quantized based on the potential energy differences between free electron orbital states.  These quantities are fixed by the physical conditions of the atom and molecules involved.  Higher internal energies (higher temperature) result in more frequent (higher amplitude) emissions.  The electrons have an equal propensity at any internal energy level to absorb and emit radiation.  Absorption occurs if the atom/mollecule is exposed to radiation from another source (like for example another atom/molecule or a black/grey body emitter).  If any given atom/molecule receives more radiation that it is capable of emitting at that temperature, it stores the energy internally and heats up until the amplitude of emission equals absorption.

From above, it should be clear that in the absence of other sources of energy, emission equals absorption when equilibrium is obtained. 

Now clearly your scenario did not involve this case so we need to go further, but I will pause here to see if we agree so far.

This thread seems to have some sort of system corruption problem.  the other posts can be viewed when you reply but don't show up on the main page.  I copied this again.


I had to dredge your response from the reply area, so clearly they come and go.

The radiation flux for the atmosphere is described by concentric layers of a sphere.  The net radiation of any given layer in equilibrium will be positive (just as you indicated might happen in your post) if that layer is receiving energy by convection and conduction and absorption of high frequency rf (sunlight) and negative if the opposite is true.  In general if any given layer is cooler than the layer below it, that layer will radiate slightly more than it absorbs while any layer slightly warmer or the same will disrupt convection and conduction and therefore generally halt this effect.  Now remember though that the layer emits and absorbs in both directions , but the slight net increase in emission will be up away from the surface and not back to earth. 

The presence of GHG in the atmosphere does "force" the earth's temperature to a higher equilibrium value that it would otherwise have without the effect, but this is true irrespective of convective and latent heat effects.  Convective and latent heat transfer has the opposite effect and dramatically cools the earth surface.  The increase in radiative transfer in the upper atmosphere provides a sink for the convective and latent heat and therefore aids cooling of the surface over what would happen without consideration of this effect.  Do you see why that is so?

None of this directly addresses the question of global climate change by variation of GHG concentration as far as I can see.