Nash bargaining solutions for international climate agreements under different sets of bargaining weights

Bargaining is a tool to share collaborative gains and to facilitate reaching agreement. To improve incentives to join an international climate agreement (ICA), the Nash bargaining solution can be used to distribute cooperative gains across signatories. In this paper, we examine how the formation of ICAs and their mitigation efficiency are impacted by the use of the Nash bargaining solution. In a Nash bargaining game with heterogeneous players, bargaining powers are unequal and may be driven by different characteristics of the players. We employ different sets of asymmetric bargaining weights in order to examine the effectiveness of climate coalitions that emerge as stable agreements. Using the Nash bargaining solution, we obtain results from the stability of coalition model (STACO). We find that the Nash bargaining solution can improve the participation incentives and performances of ICAs as compared to agreements that do not redistribute gains from cooperation, but its capacity to overcome free-riding incentives is limited. However, if Nash bargaining accounts for outside options of players, we find larger stable coalitions and higher global abatement levels. In fact, Nash bargaining with outside options can stabilise the largest coalitions that can possibly be stable in our game.