here is a link to an article by William Nordhaus about climate change policies and their economic implications. His conclusion about Kyoto:
"Climate change is a complex phenomenon, subject to great uncertainties, with changes in our knowledge occurring virtually daily. Climate change is unlikely to be catastrophic in the near term, but it has the potential for very serious damages in the long run. There are big economic stakes in designing efficient approaches to slow global warming and to ensure that the economic environment is friendly to innovation. The current international approach in the Kyoto Protocol will be economically costly and have virtually no impact on climate change. In my view, the best approach is also one that is relatively simple—internationally harmonized carbon taxes. Economists and environmentalists will undoubtedly continue to debate the proper level of the carbon price. But all who believe that this is a serious global issue can agree that the current price—zero—is too low and should be promptly corrected."If you're really interested, you can download a prepublication copy of his book A Question of Balance (Yale University Press, 2008) from his website at nordhaus.econ.yale.edu/Balance_prepub.pdf -- pay attention to Chapter 9 on discounting.