Motl, in comments, has erected a pyramid of hokum that he claims is isomorphic to the call for AGW action. To wit:
...a pyramid of roughly a dozen of assumptions and all of them need to be true at the same moment for the final conclusion to be justifiable: you need warming to exist, to continue in the future, to be caused by CO2, you need the economy to be able to reduce CO2, to make a difference, and so on.
His notion is the justification that these are independent constraints that are both of dubious truth and necessary to warrant action to prevent anthropogenic global warming. There are really only three points (a)human activity is increasing the CO2 in the atmosphere, (b)increasing CO2 increases temperature, and (c)how much? The first two of these are proven beyond reasonable doubt, and don't depend on statistical arguments. The first depends only on measurement and logic, and the second on the validity of the laws of physics. The third is difficult and the relevant lines of evidence depend on statistical and other arguments, but not in way Motl implies. Instead there are various lines of evidence (models, the historical record, the geological record) each of which give similar and mutually confirmatory evidence.
We can (and must) ask other questions. What is the cost of not acting to control our emissions? What would be the cost of acting?
My own suspicion is that we can't act decisivly in time to do much good. Thanks to the cost of acting and to the mass of lies and distortions propagated by Motl and his fellow propagandists, it seems unlikely that action will be taken. It will be a different planet our descendents (if any) inherit, and likely less hospitable to human life.