Just for the record, there is actually no real data that proves how much of man's activities are responsible for climatic changes. Climatic changes have always taken place and always will. The argument that man's activities are actually responsible for non-natural climate change comes from computer simulation models. While there is little doubt that man's activities have contributed to some of the climate change, the real question is how much: 5%, 10%, 50%?? The physics incorporated in computer simulation models is incomplete and these models, in my opinion, are not ready to be used as a tool for shaping public policy because they cannot answer the question of how much of the climate changes are do to man's activities. It is not enough to say "some of it". Full disclosure, I developed computer simulation models for the Government and I am well aware of their limitations and the assumptions used in construction such codes.