Multilateral versus sequential negotiations over climate change

We discuss a model of gradual coalition formation with positive externalities in which a leading country endogenously decides whether to negotiate multilaterally or sequentially over climate change. We show that the leader may choose a sequential path, and that the choice is determined by the convexity of the TU-game and the free-rider payoffs of the followers. Except in a few clearly defined cases, the outcome of the negotiation process is always the grand coalition, although the process may need some time. This holds for the standard IEA game with heterogeneous players even if the grand coalition is not stable in a multilateral context. We also analyse the role of a facilitating agency. The agency has an incentive to speed up intra-stage negotiations and to extend the period between negotiation stages in a sequential process.