We investigate whether global cooperation on emissions abatement can be improved if asymmetric countries agree to sign one out of several environmental agreements. The analysis is based on a two-stage game theoretical model. Conditions for stable coalitions and the resulting global emissions are determined. We allow for multiple coalitions with all countries being different, and analyze the effects in the cases of increasing marginal damages from emissions and of decreasing marginal benefits of emissions. We find that in the case of decreasing marginal benefits and constant marginal damages, admitting multiple coalitions increases the number of cooperating countries and reduces emissions (compared to the standard case with a single coalition). For increasing marginal damages and constant marginal benefits, however, multiple stable coalitions cannot coexist. If both damages and benefits are nonlinear, admitting multiple coalitions can decrease emissions. The paper thus contributes to the emerging discussion on the scope and limits of climate clubs.

中文翻译：

---

气候俱乐部与单一联盟：国际环境协议的野心

我们调查如果不对称国家同意签署几项环境协议中的一项，是否可以改善全球减排合作。该分析基于两阶段博弈理论模型。确定稳定联盟的条件以及由此产生的全球排放量。我们允许所有国家都不相同的多个联盟，并分析排放增加的边际损害和排放的边际收益减少的情况下的影响。我们发现，在减少边际收益和恒定边际损害的情况下，接纳多个联盟会增加合作国家的数量并减少排放量（与单个联盟的标准情况相比）。但是，为了增加边际损害赔偿和恒定的边际收益，多个稳定的联盟不能共存。如果损害和利益都是非线性的，则加入多个联盟可以减少排放。因此，本文有助于就气候俱乐部的范围和限制进行新的讨论。