Can anyone help with these questions?

1. Between what altitudes does 90% of the effect of CO2 occur ?  
2. Do you have a graphic for a multi layer model of the atmosphere ?  
3. How many layers did Gilbert Plass use ?

From a personal communication with Kevin Trenberth:

Trenberth, K. E., and L. Smith, 2005: The Mass of the Atmosphere: a Constraint on Global Analyses. J. Climate, 18, 864-875.

With regard to the questions you pose. See below. The atmosphere has about the same gas constants up to about 80 km altitude. It is not well mixed wrt water vapor or ozone. Above 80 km the molecular weight changes and then the atmosphere becomes ionized (the ionosphere) and at that point the concept of temperature breaks down as the mean free path between molecules is too long.

To me the important consideration is the mass of the atmosphere in the layer. If the layer is radiating it loses energy and the temperature drops, and it can drop a lot. It can be in equilibrium if it is compensated by radiation received. But that means the gas has to be a continuum and molecules in contact. But the import of all this has to relate to the total energy which brings in the mass.

It is important to resolve the vertical structure of the atmosphere but if one does that by mass layers then the whole of the atmosphere above 30 km is in the top 1% wrt mass.

Hope some of that was applicable.

Looking back, maybe not so much

I can't help much John but one observation. The altitude range for the GH Effect is wavelength dependent. In those bands where H2O is at play the upper altitude is much lower since H2O condenses out with altitude. CO2 and Ozone are much higher, seemingly up into the stratosphere at the centre of their bands. In fact the relatively constant brightness temperature you see at the bottom of the CO2 'notch' probably says that in those bands Top of Atmosphere is above the Tropopause, in the lower Stratosphere where temps are steady. The central spike in the notch will be even higher, up where the stratosphere ais actually warming with altitude. The edges of the notch probably reflect an ever decreasing altitude until it merges into the H2O region.

I don't know haw many layers Plass used. It couldn't have been many or the valves on the old computer would have started melting.

Just a few pointers:

Carbon dioxide atmospheric vertical profiles retrieved from space observation using ACE-FTS solar occultation instrument.

Weak Northern and Strong Tropical Land Carbon Uptake from Vertical Profiles of Atmospheric CO2.

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