"Alastair" wrote:

....
The models are fatally flawed because the radiation emitted
by the surface is totally absorbed near the surface (in the
boundary layer) as Barrett points out. So increasing CO2 does
not affect the radiation out to space.

I think the idea is that increasing CO2 reduces the IR radiation to space
from the atmosphere, and that then increases the heat content of the entire
climate system. I don't know how many atmospheric layers a climate model
typically has, but the effect has to percolate downwards to the surface, and
that's how the models reproduce the global warming effect of increasing
atmospheric CO2.