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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.

Under what conditions should we expect the United States to support international enforcement of treaties? We hypothesize that U.S. support is most likely for treaties where international enforcement will cause considerable (desired) behavioral change by other countries but little (undesired) behavioral change by the United States. Similarly, U.S. support is least likely for treaties where international enforcement will generate the converse effects. In developing this hypothesis, we derive specific conditions under which we should expect U.S. benefits of international enforcement to outweigh U.S. costs (or vice versa). We also provide empirical examples. Finally, we consider three alternative explanations of U.S. views on international enforcement—concern for U.S. sovereignty, desire to prevent infringements on U.S. constitutional protection of individual rights, and the usefulness of international enforcement as a domestic commitment device. We discuss these alternative explanatory factors' relationship to our own hypothesis.

Under the 2015 Paris climate agreement, each Party sets its own mitigation target by submitting a Nationally Determined Contribution (NDC) every five years. An important question is whether including conditional components in NDCs might enhance the agreement s effectiveness. We report the results of a closely controlled laboratory experiment based on a mixed sequential-simultaneous public good game with one leader and three followers that helps answer this question. The experiment investigates how two factors infl uence the effectiveness of leadership based on intrinsically conditional commitments. Measuring e¤ectiveness in terms of followers ' and total contributions, we find that it may help if the conditional promise is credible and if its implementation in fluences followers' welfare substantially. Importantly, however, for both factors we fi nd a signi cant effect only if the leader does not reap disproportionate gains from the group' s efforts. These fi ndings have important implications concerning the future success of the Paris agreement. This is a pre-copyedited, author-produced version of an article accepted for publication in Oxford Economic Papers following peer review. The version of record is available online at: http://dx.doi.org/10.1093/oep/gpx045

Enforcement of agreements can be a major challenge in international politics. However, the interest in mechanisms of self-enforcement seems significantly lower among scholars studying international peace agreements (IPAs) than among scholars studying international environmental agreements (IEAs). Moreover, practically no exchange of ideas and findings about enforcement can be found between these two fields of research. We argue that a combination of similarities and differences between the two issue-areas provides fertile ground for mutual learning. To facilitate communication we develop a unifying but differentiated definition of self-enforcing agreements (SEAs). We then use this conceptual framework to explore lessons about IEA design that might be learned by studying IPAs and lessons about IPA design that might be learned by studying IEAs. We submit that this kind of compare-and-contrast analysis may provide important input for the development of a more refined and general theory of SEAs.

The limited success of the UNFCCC negotiations has enticed scholars, environmentalists, and policymakers alike to propose alternative approaches to climate cooperation. This article reviews the scholarly literature concerning one such proposed alternative—climate clubs. According to the club approach, it would be promising to start with small groups of “enthusiastic” countries. These countries would outline what they are willing and able to do, conditional on what other enthusiastic countries offer and implement. Moreover, these enthusiastic countries would try to entice “reluctant” countries to join via “exclusive and contingent” measures. Focusing on the conditions for a climate club to effectively reduce global emissions, we organize our review around four main questions: first, what is a climate club’s potential for providing benefits that accrue exclusively to club members? Second, how might leadership influence a climate club’s ability to eventually become effective? Third, what insights can the formal modelling literature offer concerning the effectiveness of climate clubs? Finally, which is the empirical record of existing climate clubs? We conclude by providing several suggestions for future research.

According to two-level game theory, negotiators tailor agreements at the international level to be ratifiable at the domestic level. This did not happen in the Kyoto negotiations, however, in the US case. We interviewed 26 German, Norwegian, and US participants in and observers of the climate negotiations concerning their views on three explanations for why the United States did not become a party to Kyoto. Explanation 1 argues that Kyoto delegations mistakenly thought the Senate was bluffing when adopting Byrd–Hagel. Explanation 2 contends that Europeans preferred a more ambitious agreement without US participation to a less ambitious agreement with US participation. Finally, explanation 3 suggests that in Kyoto the Clinton–Gore administration gave up on Senate ratification, and essentially pushed for an agreement that would provide them a climate-friendly face. While all explanations received some support from interviewees, explanation 1 and (particularly) explanation 3 received considerably more support than explanation 2.

We identify and explain significant differences between the compliance enforcement systems of three cap-and-trade programmes: the European Union’s Emission Trading Scheme (EU-ETS), the US SO2 emission trading programme and the Kyoto Protocol. Because EU-ETS’s compliance enforcement system is somewhat less potent than that of US SO2, but vastly more potent than Kyoto’s, it might be tempting to predict that EU-ETS will (1) not quite achieve the SO2 programme’s near-perfect compliance rates, yet (2) achieve significantly better compliance rates than Kyoto. However, we offer a novel theoretical framework suggesting that how compliance enforcement affects compliance will depend on how the emission trading programme addresses participation. We conclude that while (1) will likely prove correct, (2) will not; Kyoto may even outperform EU-ETS compliance-wise because whereas EU-ETS (and US SO2) specify mandatory participation, most Kyoto member countries participate voluntarily.

Several scholars have suggested that the United States can be compelled to reengage in the Kyoto process by linking cooperation on climate change to cooperation on trade or technology research and development. We argue that such issue linkage would likely fail and suggest that a more promising road to U.S. cooperation is to develop an alternative climate agreement based on federal U.S. climate policy. However, the question then becomes whether the Kyoto countries might be prepared to abandon the Kyoto process in favor of such a U.S.-based agreement. We argue that if a U.S.-based agreement were to be built on President Bush's current climate policy, the Kyoto countries (especially the European Union) would likely be reluctant to go along. However, if a U.S.-based agreement were to be built on the many Kyoto-like initiatives now emerging at state and local levels, the Kyoto countries might well be more favorably inclined.

The US government is being pressured by both international and domestic influences to re-engage in international climate control. This paper considers whether the international “pull” and the domestic “push” will be strong enough to accomplish this. First, we discuss whether changes in the architecture of the current climate regime might induce the United States to re-engage at the international level. We argue that the United States is unlikely to rejoin any global climate regime that is based on the Kyoto architecture, even if Kyoto were to be “reformed”. Second, we discuss whether domestic political developments might eventually cause the United States to re-engage. We conclude that US re-engagement is likely to require the emergence of a new climate regime that basically extends US regulation to other countries. However, the forging of a unified US climate policy is still in the making. Furthermore, a new regime can gain widespread participation only if the Kyoto countries accept the idea of replacing Kyoto with some alternative architecture, which seems unlikely in the near future.

This paper considers whether international environmental public goods provision, such as mitigation of climate change, is better dealt with through regional cooperation than through a global treaty. Previous research suggests that, at best, a global environmental treaty will achieve very little. At worst, it will fail to enter into force. Using a simple dynamic game-theoretic model, with weakly renegotiation-proof equilibrium as solution concept, we demonstrate that two agreements can sustain a larger number of cooperating parties than a single global treaty. The model provides upper and lower bounds on the number of parties under each type of regime. It is shown that a regime with two agreements can Pareto dominate a regime based on a single global treaty. We conclude that regional cooperation might be a good alternative–or supplement–to global environmental agreements.

The United States, the world's largest emitter of greenhouse gases, is not going to ratify the Kyoto Protocol in the foreseeable future. Yet, a number of countries have decided to stay on the Kyoto track. Four main explanations for this apparent puzzle are considered. The first is that remaining Annex I countries still expect the Kyoto Protocol to reduce global warming sufficiently to outweigh the economic costs of implementation. The second is that the parties, by implementing the treaty, hope to induce non-parties to follow suit at some later stage. A third hypothesis is that EU climate institutions have generated a momentum that has made a change of course difficult. Finally, Kyoto's persistence may be linked to the European Union's desire to stand forth as an international leader in the field of climate politics. We conclude that the first two explanations have little explanatory power, but find the latter two more promising.

More than two decades of climate change negotiations have produced a series of global climate agreements, such as the Kyoto Protocol and the Copenhagen Accords, but have nevertheless made very limited progress in curbing global emissions of greenhouse gases. This paper considers whether negotiations can succeed in reaching an agreement that effectively addresses the climate change problem. To be effective, a climate agreement must cause substantial emissions reductions either directly (in the agreement's own lifetime) or indirectly (by paving the way for a future agreement that causes substantial emissions reductions directly). To reduce global emissions substantially, an agreement must satisfy three conditions. Firstly, participation must be both comprehensive and stable. Secondly, participating countries must accept deep commitments. Finally, the agreement must obtain high compliance rates. We argue that three types of enforcement will be crucial to fulfilling these three conditions: (1) incentives for countries to ratify with deep commitments, (2) incentives for countries that have ratified with deep commitments to abstain from withdrawal, and (3) incentives for countries having ratified with deep commitments to comply with them. Based on assessing the constraints that characterize the climate change negotiations, we contend that adopting such three-fold potent enforcement will likely be politically infeasible, not only within the United Nations Framework Convention on Climate Change, but also in the framework of a more gradual approach. Therefore, one should not expect climate change negotiations to succeed in producing an effective future agreement—either directly or indirectly.

This is the originally published version of the article, as published in the journal, available here: www.ejge.org (Open Access) Elected representatives serving their final period face only weak incentives to provide costly effort. However, overlapping generations (OLG) models suggest that exit prizes sustained by trigger strategies can induce representatives in their final period to provide such effort. We evaluate this hypothesis using a simple OLG public good experiment, the central treatment being whether exit prizes are permitted. We find that a significantly higher number of subjects in their final period contribute when exit prizes are permitted. However, this result does not originate from use of trigger strategies. More likely explanations include gift-exchange and focal-point effects.

This is an Accepted Manuscript of an article published by Taylor & Francis in Climate Policy on 12 Jun 2012, available online: http://www.tandfonline.com/doi/full/10.1080/14693062.2012.692206 The compliance enforcement system of the Kyoto Protocol provides only weak incentives for Parties to comply with their commitments. For example, the penalties for non-compliant countries are not legally binding, and moreover, there is no second-order punishment for those countries that fail to implement them. Thus, a Party can simply refuse to comply without consequence. The alternative compliance enforcement systems that have been proposed in the literature also face substantial problems. A simple, flexible, potent, and credible compliance enforcement system for a post-Kyoto climate agreement, based on deposits, is proposed here: at ratification, each country deposits a significant amount of money, and continues to do so in the preparation stage each year until the start of the commitment period. At the end of this period, those countries that meet their emissions limitation targets receive a full refund of their deposit, while those that fail to do so forfeit part or all of it. A simplified two-country model of the deposit system and a numerical example of an agreement involving the US, Japan, Russia, and Europe is also provided. If each country’s deposit is no less than its abatement costs, there is a strong incentive for participating countries to avoid noncompliance.

The circumstances under which it pays for an outsider to join an existing group of collaborators are investigated, using the compound Prisoner's Dilemma supergame as a model. Two different regimes are considered; one where discriminating behaviour is allowed, one where it is effectively banned. It is shown that an incentive for outsiders to join the colluders may exist in the former case, but not in the latter. In the latter case, however, a substitute for this incentive can sometimes be created, by threatening collective defection from the colluding group, unless the relevant outsider(s) join(s) in.

The essay offers a review of Steven J. Brams' book Superpower Games. In this book, Brams uses 2 x 2 games to investigate important aspects of the superpower relationship. Particular attention is given to problems of deterrence, armaments, and verification — the aim being partly to explain actual behavior by the superpowers, and partly to provide possible solutions to their dilemmas. A number of models are presented and analyzed with great skill and imagination. In some cases, Brams considers the possibility that the players use probabilistic strategies, while in others, the models are analyzed by invoking the so-called Theory of Moves. While the present essay stresses the importance of some of Brams' results, it also questions the relevance of his argument at a few points. In particular, it is argued that the Theory of Moves may be less widely applicable than Brams seems to believe.