Here is my take on the issue. Please feel free to provide any input you have on this topic.
The question I asked of everyone was what would the temperature of the Earth be if everything else was held constant except there was no CO2 in the atmosphere.
So questions of albedo and clouds must be ignored. Another thread can discuss the legitimacy of such feedbacks, but the question I want answered by everyone is what would the Earth’s temperature be if there was no CO2.
My approach was to determine the total net energy that is transferred from the surface to the atmosphere. I used Kiehl-Trenberth 1997 and 2008 and others. While slight differences existed the overall result is that there is 120 W/m^2 of energy transferred to the atmosphere by the Earth’s surface. This is 71% of the total energy that is absorbed by the surface from the Sun.
I then broke down each transfer mechanism. Here is the end result as shown in my book.
Evaporation: 80.0 W/m^2
Water vapor (GHG): 18.1 W/m^2
Convection: 17.0 W/m^2
CO2 (GHG): 3.3 W/m^2
Ozone (GHG): 1.0 W/m^2
Other (GHG): 0.7 W/m^2
This total energy transfer is consistent with the daily temperature cycle that exists in the atmosphere. I can provide more details on that if anyone is interested.
Since the accepted value of the total GHE is 33 °C, I used each proportion of energy to the 33 °C. The result was as follows:
Evaporation: 22.0 °C
Water vapor (GHG): 5.0 °C
Convection: 4.7 °C
CO2 (GHG): 0.9 °C
Ozone (GHG): 0.3 °C
Other (GHG): 0.2 °C
If CO2 were removed, the change in energy transfer would be 3.3 W/m^2 which is 2.75% of the total. That change corresponds to a total change to the GHE of 0.9 °C which I will consider 1 °C as the ozone transfer really takes place in the stratosphere.
Since the Earth’s temperature is ~287K, the temperature of the Earth without CO2 would be ~286K.