CO2 Contributes 1.3% Of The Greenhouse Effect In The Tropics

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.

1. 0 ppm   392.3 w/m²
2. 364 ppm   397.5 w/m²
3. 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.

1. 0 ppm   372.8 w/m²
2. 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.