Clive – “that assumes the models are a correct description of nature.”
Yes. The IPCC assumes that the principle factors in their models are correct descriptions of nature.
As R. Gates suggests, the physics of the basic factors in the model are reasonably well understood. The models use our best scientific estimates of those fundamental processes and combine them into a model to understand/explore/test how they work together.
Given confidence in the basic inputs of the models, the models as a whole are basically treated as correct descriptions of nature. There is additional energy being recycled (by GHG) into the system which is being absorbed by the system (Oceans). That energy must go somewhere and in the process it will change the variables that drive our climate.
Now, HOW does all of that happen? Our understanding is limited, but that does not mean it is absent. We are learning more as we go. However, the HOW energy builds up in the system is not as critical to the discussion at hand as the THAT it is building up.
Of course, one can certainly challenge the idea THAT GHG are causing more energy to be contained in the system. However, if your challenge consists of stating that “SOMETHING” is releasing the energy from the system “SOMEHOW” – and you don’t have a proposed mechanism (HOW) to describe the THING that is releasing the energy … your challenge can seem a bit weak.
Yes?