We study international environmental agreements in a setting that incorporates catastrophic climate change, and sovereign countries, who are heterogeneous in their exposure to climate change. This leads to a stochastic game with an absorbing state whose equilibrium structure is very different from the infinitely repeated games that are usually studied in the literature on environmental agreements. In particular there is no folk theorem that guarantees that the social optimum can be sustained in a Nash equilibrium as long as players are sufficiently patient. However, in most circumstances, it is feasible to implement an abatement scheme with a level of aggregate abatement that is close to the social optimum. Moreover, the discount rate has a non-monotonic effect on the optimal environmental agreement.