This article wasn’t supposed to be so long, but it is important to understand the science behind the Greenhouse Effect (GHE). My view is that net energy transfer to the atmosphere is the primary driver of the warmer atmosphere and the GHE. While that isn’t currently the conventional approach, there is nothing that precludes it from being a better approach and there are some benefits.
The first benefit is that the ratio’s of convective and radiative heat transfer are more in line with each other. In a typical situation with a 10-20 °C temperature difference between objects, the ratio of energy transfer between natural convection and radiative transfer should be of a comparable order of magnitude. The net transfer shows a ratio of 0.74. That the atmosphere doesn’t absorb all the energy skews the ratio a little. The FT08 gives a ratio of 0.05. This equation was modified for the horizontal surface for the Nusselt number from the basic derivation here. This case is limited to small temperature gradients.
One benefit from my view is that it allows the different components of the overall GHE to be directly weighted and compared to each other. If the assumption is made that half of the energy absorbed by the stratosphere (78 W/m2 total) and the other half by the troposphere, then the total energy radiated up by the troposphere is 159 W/m2. If that energy is the primary cause of the GHE, then 159 W/m2 of energy is causing the 33 °C GHE.
Evaporation / Transpiration:
This is the largest source of energy transferred to the troposphere at 80 W/m2. This accounts for 50.3% of the total. If it is the same ratio of the GHE, then this accounts for 16.6 °C of the GHE. When liquid water evaporates it takes energy away from the surface. This causes a cooling effect at the surface. When water vapor condenses in the atmosphere (to make clouds or fog depending on where it happens) the energy is then transferred to the atmosphere. This is only part of why water is the most important part of the GHE.
Direct absorption from the Sun
78 W/m2 of energy are directly absorbed by the atmosphere. This is divided up into two parts. The ozone layer strongly absorbs the different wavelengths of shortwave (SW) energy from the sun. This is why the stratosphere is warm. Almost none of the very high energy UV from the sun reaches the surface of the Earth.
The 2nd part is absorbed in the lower atmosphere by water vapor. Since water vapor is very rare above the troposphere, the energy that can be absorbed by water vapor is absorbed in the troposphere. The precise breakdown is difficult because clouds really alter this. I will simply split the total in half. It is probable that the stratosphere gets more than the troposphere. The effect of that change would be to decrease the direct portion of the GHE.
If the troposphere does get 39 W/m2 then it is the 2nd most important part of the GHE at 24.5%. CO2 does absorb a small portion of this amount, but at 1% it is not very significant and that absorption would take place much higher in the atmosphere as the CO2 concentration is mostly constant in the atmosphere.
Greenhouse Gas Absorption
At 23 W/m2 the absorption of longwave energy from the surface is 14.5% of the 33 °C total, or about 4.8 °C. Of that water vapor is the most important. It causes between 60-80% depending on cloud cover. KT97 puts the clear sky at 60% and the cloud estimates put it around 80%. Regions with high humidity also favor water vapor over CO2.
CO2 on average is 15-18% of the greenhouse gas absorption, or it is responsible for 0.72-0.86 °C of the total GHE. If changing CO2 levels did increase this by a few percent, the contribution of CO2 would then be 0.74-0.88 °C. This is a part of why I remain unconvinced that CO2 is capable of causing significant global warming.
Convection / Thermals
Last and actually least is direct convection of the air caused by the air collisions with the warm ground. This warms the air which then circulates. At 17 W/m2 it is the smallest contributor to the GHE at 10.7% of the total. This means that convection by itself contributes 3.5 °C of the GHE. Or about the same as water vapor by itself.
Here is a NASA picture that uses percentages of the total incoming solar energy to show the atmospheric energy balance. You will see it is very similar to my own.