What is Wrong with Global Warming Anyway? David Friedman

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Extracts:

The usual argument to show that an increase in global temperatures by a few degrees centigrade over the next century would be a catastrophe, or at least a very bad thing, consists of pointing out specific bad effects: rising  sea level increasing the risk of flooding in very low lying areas, rising temperature making particular areas less suited to growing the crops they now grow. But an increase in global temperature would also have good effects, as should be obvious to anyone who has ever spent a winter in Chicago, not to mention Alaska or Siberia. The question is not whether there are any bad effects but whether there are net bad effects, whether the increased risk of flooding in Bangladesh does or does not outweigh the opening of a sea route north of Asia and the increase in the habitable area of Canada and Siberia.

The answer, I think, is that 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?

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.

Vía Francisco Capella.