George Carlin says that optimists see the glass as half full, pessimists see the glass as half empty, and he sees the glass as too big. Some people are optimistic about international environmental agreements. Many people think that the Montreal Protocol has done a wonderful job, for example. Within that optimistic camp, there are even divisions of optimism and pessimism, with some double-optimists believing that the Montreal Protocol represents a triumph over a global problem of daunting scientific complexity, while the less optimistic temper their enthusiasm for the general applicability of the ozone example by pointing to the paucity of actors involved and the ready availability of economically viable substitutes for the relevant pollutants.

David Freestone is an optimist about the Kyoto Protocol because he believes that it has promoted cost internalization among European executives in connection with a European trading system that, while not directly mandated by the Protocol, clearly has its genesis in that agreement. Some people are pessimistic about international environmental agreements. Pessimists might point to the fact that the Kyoto Protocol does not bind the United States, the largest current producer of greenhouse gases.

The Kyoto Protocol does not even attempt to impose binding reductions upon China and India, who are sure to become colossal producers of greenhouse gases in the not-too-distant future. And many believe that the targets of the Kyoto Protocol are much too modest. Similarly, the Biodiversity Protocol has not generated much enthusiasm. Membership is broad, but commitments are shallow. If you listen to enough of these evaluations, however, then you begin to realize that a good deal of them depend on how large the evaluator is making his or her glass.

John K. Setear, Carlin and Collapse, 101 American Society of International Law Proceedings 171–172 (2007).