Regional variation, holdouts, and climate treaty negotiations

We develop a model of international agreements to price a transboundry externality and provide a new heuristic to aid in interpreting negotiation behavior. Under conservative assumptions, a country’s net benefits will be positive under an efficient pollution price if its share of global damages is less than half its share of worldwide abatement costs. We solve for a permit allocation scheme consistent with that heuristic such that every region will have positive net benefits in an agreement to price the pollution externality at the globally efficient level. We then apply this framework to climate change using regional data from Integrated Assessment Models and test the feasibility of a global climate change treaty. The results indicate that several regions have positive net benefits from a globally efficient price on carbon, including Western Europe, South Asia (including India), and Latin America. We then solve for a permit allocation scheme that should produce worldwide agreement on a climate treaty. Using the same model, we show that differential carbon taxes aimed at producing universal agreement would produce tax rate differences of an order of magnitude. We also argue that shares of global GDP might be an appropriate proxy for exposure to climate damages and find that a global climate treaty would be cost-benefit justified for all countries without transfers when that assumption is used.