IMO, there is plenty of evidence out there to demonstrate that man can contribute to warming. The problem is, of course, figuring out how much. The cost of action is rather immediate and directly impacts the country taking action. The cost of inaction has large error bars, is delayed, and may or may not affect the country taking action as largely as it would, perhaps, other nations. Sounds like a an issue that easily becomes political.
The necessity for action is largely where the political debate should lie. The concept of AGW to me is largely settled. Man, through CO2 emissions, contributes to the greenhouse gas effect and thus warming. How much is the scientific question of merit....and the climatologists seem to be gaining confidence in their estimates, but that is certainly open for scientific debate....and has been debated....and will continue to be, but I think that the ranges are possible (though I believe the probabilities assigned to these ranges are likely still wrong). What is open to even more debate is the question of what the effects of this warming will be.
