The atmosphere is a commons and this situation is the tragedy of the commons. In the language of the classic sheep-grazing commons, each player has incentive t

The atmosphere is a commons and this situation is the tragedy of the commons. In the language of the classic sheep-grazing commons, each player has incentive to put an extra sheep in the commons -- that is, to defect. Everyone loses, but that player benefits in the short term. With cars, by defecting -- that is, allowing its car makers to sell less-regulated cars -- the U.S. gets to sell more profitable cars, despite polluting the atmosphere for everyone else (and, shortsightedly, us too).