While the techniques and experiments used to link cancer to tobacco and human activities to global change are, as you point out, different, the scientific process underlying both is pretty much the same: research is conducted, the results are published in peer-reviewed publications and scrutinized and checked by workers in the field, and a consensus is arrived at by scientists working those fields. Subsequent research either strengthens or weakens that consensus. I'm confused about why you are perfectly willing to accept the consensus of experts that smoking causes cancer, but not the consensus of experts that human activities are the primary cause of global climate change. The skeptics and deniers in both the tobacco-cancer and anthropogenic climate change are either a very small number of scientists employed by the tobacco and fossil fuel industries or they are cranks that have no background in these fields. Boulderhawk once trotted out on this board the writings of a fellow, whose name escapes me at the moment, as a source arguing against the reality of climate change. This guy had no training in climatology, ecology or earth science. His academic credentials consisted of an MS in English Lit with a specialization in W.B. Yeats. Am I going to take his word over the word, the consensus, of hundreds of scientists belonging to the National Academy of Sciences?
You seem to be resistant to the notion that their are some scientific issues for which the science IS settled. Evolution is such an issue and the primary cause of climate is another. But, if your source of information on the latter topic is the mainstream media or the internet, you are properly unaware that this is a settled issue among the experts.
