Game theory came handy during the Cold War, when there were two big players, both of whom had fairly clear choices of what do to, as well as reasonably credible information about the consequences of their actions. Not surprisingly, it was used mainly in simulations of military conflict. Is this the case with climate change, though? Following Robert Axelrod, who showed that games change dramatically when they are played repeatedly, Michael Liebreich argues in a recent paper that it is (“Playing Games with the Planet,” September 29, 2007). Besides, he comes to rather optimistic conclusions about international cooperation in the implementation of treaties such as the Kyoto Protocol, which come up for revision from time to time. On such occasions, those who misbehave can be punished and thus forced to cooperate. Splendid. But any game with so many small players, all of whom have quite hazy choices of what to do and pretty lousy information about the consequences of their actions, is likely to become indeterminate, especially if it is played repeatedly. In addition, the clarity of military structure is gone when it comes to other branches of government, let alone all the economic sectors involved in curbing climate change. In short, playing games with the planet is liable to remain just that: playing games.