Tragedy of the Commons
Philosophers refer to it as the tragedy of the commons. In Britain, pastures used to be held in common. If farmers grazed too many cattle on them, the pasture was destroyed. If an individual farmer reduced the number of cattle, he did not benefit unless other farmers reduced as well.
We have a similar problem with CO₂. If one country cuts back, but other countries continue to emit, the entire atmosphere is still poisoned.~ Roedy (1948-02-04 age:69)