Well, TBH, I was making many assumptions, but they were reasonable. (It was some time ago and repeating from memory, not an exercise I would like to repeat). From memory, it has 60% more solar energy in, but less after reflection at the edge of the atmosphere. That different lower energy input on a higher pressure of gas by default accounted for almost all of the temperature differences. Other factors I've raised was enthalpy (in air, not for HVAC) the charts consider temperature, humidity and altitude (air density) CO2 is irrelevant to where in high co2 environments like mines they will have the chart adapted for the difference at the expected co2 levels. And when CO2 can be up to 10k ppm before any breathing difficulties begin, 400ppm is hardly like "drinking too much water is bad" like normies often bring up.