It would seem to me that chaos theory would suggest that it is impossible to predict with any degree of certainty any claims of future global warming specificially due to man. Too many variables, too many assumptions or simplifications/etc. in variables.
I think you have a good point there.
UN IPCC WG1 Technical Summary (TS) and expert review draft TAR, Chapter 14:
"The climate system is a coupled non-linear chaotic system, and therefore the long-term prediction of future exact climate states is not possible. Rather the focus must be upon the prediction of the probability distribution of the systems future possible states by the generation of ensembles of model solutions..."
"In sum, a strategy must recognize what is possible. In climate research and modeling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that the prediction of a specific future climate state is not possible. The most we can expect to achieve is the prediction of the probability distribution of the system's future possible states by the generation of ensembles of model solutions. This reduces climate change to the discernment of significant differences in the statistics of such ensembles. The generation of such model ensembles will require the dedication of greatly increased computer resources and the application of new methods of model diagnosis."