We analyze the design of an international climate agreement. In particular, we consider two goals of such an agreement: overcoming free-rider problems and adjusting for differences in mitigation costs between countries. Previous work suggests that it is difficult to achieve both of these goals at once under asymmetric information because countries free ride by exaggerating their abatement costs. We argue that independent information collection (investigations) by an international organization can alleviate this problem. In fact, though the best implementable climate agreement without investigations fails to adjust for individual differences even with significant enforcement power, a mechanism with investigations allows adjustment and can enable implementation of the socially optimal agreement. Furthermore, when the organization has significant enforcement power, the optimal agreement is achievable even with minimal investigative resources (and vice versa). The results suggest that discussions about institutions for climate cooperation should focus on information collection as well as enforcement.

我们分析了国际气候协议的设计。特别是，我们考虑了此类协议的两个目标：克服搭便车问题和调整国家之间缓解成本的差异。以前的工作表明，在信息不对称的情况下很难同时实现这两个目标，因为各国通过夸大减排成本来搭便车。我们认为，国际组织的独立信息收集（调查）可以缓解这个问题。事实上，尽管没有调查的最佳可实施气候协议即使具有强大的执行力也无法针对个体差异进行调整，但具有调查的机制允许调整并能够实施社会最优协议。此外，当组织拥有强大的执法权时，即使调查资源最少（反之亦然），也可以达成最佳协议。结果表明，关于气候合作机构的讨论应侧重于信息收集和执法。