Although the Paris Agreement arguably made some progress, interest in supplementary approaches to climate change co-operation persist. This article examines the conditions under which a climate club might emerge and grow. Using agent-based simulations, it shows that even with less than a handful of major actors as initial members, a club can eventually reduce global emissions effectively. To succeed, a club must be initiated by the ‘right’ constellation of enthusiastic actors, offer sufficiently large incentives for reluctant countries and be reasonably unconstrained by conflicts between members over issues beyond climate change. A climate club is particularly likely to persist and grow if initiated by the United States and the European Union. The combination of club-good benefits and conditional commitments can produce broad participation under many conditions.

Climate engineering in general and solar radiation management (SRM) in particular raise profound and complex political, legal, social, and ethical questions that go well beyond technical feasibility issues. We consider three such questions. First, can existing EU decision-making processes accommodate sufficient public engagement to ensure legitimate decisions on SRM? Second, does politics influence the choice of legislative procedure for SRM regulation? Third, does the choice of legislative procedure influence the likelihood of SRM implementation? Three main conclusions emerge from our analysis. First, existing EU decision-making processes can – given certain conditions – accommodate considerable public engagement and hence ensure legitimate decisions on SRM. Second, politics matters; indeed, the EU's choice of legislative procedure concerning SRM may well become subject to political negotiations. Finally, the choice of legislative procedure may substantially influence the likelihood of SRM implementation.

To enhance effective cooperation, the Marrakesh Accords provide a compliance system for the international climate regime. An innovative part of this system is an Enforcement Branch authorised to apply punitive consequences against countries that fail to comply with their Kyoto obligations. While previous research has primarily focused on the ability of this compliance system to deter non-compliance, this article discusses whether the actual use of punitive consequences will induce a non-compliant country to return to compliance. The Marrakesh Accords explicitly emphasise that the punitive consequences shall be aimed at the restoration of compliance. However, we show that the application of punitive consequences will accomplish this in only exceptional circumstances.

Previous research has documented only a modest success rate for imposed sanctions. By contrast, the success rate is higher in cases that are settled at the threat stage. In this article, the authors provide new insights about the circumstances under which sanctions cause behavioral change only after being imposed. First, the target must initially underestimate the impact of sanctions, miscalculate the sender's determination to impose them, or wrongly believe that sanctions will be imposed and maintained whether it yields or not. Second, the target's misperceptions must be corrected after sanctions are imposed. A game-theoretical model with incomplete information is used to develop and clarify the argument.