I took the radiate transfer model used by NCAR (RRTM) and ran it with tropical humidity (0.025 mole fraction H2O) and three levels of CO2. Results are shown below.
- 0 ppm 392.3 w/m²
- 364 ppm 397.5 w/m²
- 3640 ppm 403.8 w/m²
CO2 contributes almost nothing to the greenhouse effect in the tropics. The removal of all CO2 would only lower downwelling longwave radiation by 1.3%. A 10X increase in the amount of CO2 would only increase downwelling longwave radiation by a little over 1%.
At lower surface humidity (0.015 mole fraction H2O), co2 contributes about 2.5% of the greenhouse effect.
- 0 ppm 372.8 w/m²
- 364 ppm 381.3 w/m²
The role of CO2 is wildly exaggerated by alarmists. Gavin typically uses a number somewhere around 30%, when in fact the real number is less than 5% over most of the Earth’s surface.