Sigh The model used by RS in  is very primitive its not a GCM its a d RC model It was refuted a long time ago In fact its selfrefuting as they say in the paper the model is only suitable for studying small perturbations but they use it for large ones I recommend reading note  to the article As everyone has pointd out to you the logarithmic nature is well known its in all the current GCMs the results you refuse to believe incorporate it it is not in dispute