Most people are surprised to hear that the estimated amount of the GHG effect that is attributed to CO2 in the scientific literature is a range from as low as 2 % to as high as 45 %. The amount of effect will vary with latitude, altitude, time of day/night, over land/water, season, cloud cover/type and humidity, etc. so finding an average that applies over a year or decades is a tall order. The climate models use values in the 20 to 30 % range.
As month after month goes by with the models running too hot the big question about basic assumptions comes to the top. Where are the assumptions wrong? Where are the blind spots that prevent these otherwise “brilliant researchers” from seeing the potential holes in their theories?
Climate sensitivity to changes in CO2 and the changes in forcings and the positive and negative responses to those forcings will all be non linear and change with time. The system will work its way towards an equilibrium and there will be responses to balance or offset the positive feedbacks. The amount of energy lost to space will increase or cloud cover will change and reduce the energy imbalance. There are events in geological history which change global temperatures to a new equilibrium for a period but changes in CO2 content does not have much support as a control knob in geological history.
The estimates of Climate Sensitivity are based on many assumptions but the most basic assumption is the amount of greenhouse effect that is attributed to CO2. There appears to be no way to empirically determine that amount but the estimates will continue to decrease as the bust in the model predictions grows.