What is Wrong with Global Warming Anyway? por David D. Friedman:
.. nobody knows if the net effects would be good or bad, and probably nobody can know. We are talking, after all, about effects across the world over a century. How accurately could somebody in 1900 have predicted what would matter to human life in 2000? What reason do we have to think we can do better?
.. The earth and its climate were not, after all, designed for our convenience, so there is no good reason to believe that their current state is optimal for us ..
If we have no good reason to believe that humans will be substantially worse off after global warming than before, we have no good reason to believe that it is worth bearing sizable costs to prevent global warming.