Climate Scientists believe All Factors Including CO2 (AFIC) is the control variable with much weight given to CO2. With that, CO2 primarily controls Temperature. It is suggested that at equilibrium, Temperature becomes the control variable for AFIC. The graph illustrates the slope reversal at equilibrium. At equilibrium CO2’s affect is overwhelmed by all other factors.
Climate Scientist believe it is pretty much a) with AFIC controlling Temperature. The Alternate theory is a) and b) with Temperature controlling AFIC at equilibrium. This is possibly consistent with step changes a la Tisdale and Trenberth, climate regime changes and the hiatus.
Edit: It might help to think of it as a Z curve.
Idea inspired by Willis Eschenbach.