I admit to not really following your comments, in particular this one.No you are wrong.
My understanding is that the atmosphere is matter. Some of that matter is warmed by the surface of the earth. Of concern in that regard is CO2, a well mixed gas, which is being emitted by human activity. If we measure the temperature of that matter at a particular place, it is argued that over time - all other things being equal - the average temperature will increase. This is because the number of molecules of CO2 in the atmosphere has increased. It follows that if the number of molecules of CO2 were to decrease, the temperature would decrease. This is the basis for arguing in favour of lowering emissions.
If the concentration of GHG molecules is less, the temperature of the atmosphere is less. So surely it follows that were the earth's atmosphere less dense but retained the same relative proportions of gasses as today, the temperature at the same place I mention above would be lower.
Why am I wrong to infer this?