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Using a novel agent-based model, we study how US withdrawal might influence the political process established by the Paris Agreement, and hence the prospects for reaching the collective goal to limit warming below 2°C. Our model enables us to analyze to what extent reaching this goal despite US withdrawal would place more stringent requirements on other core elements of the Paris cooperation process. We find, first, that the effect of a US withdrawal depends critically on the extent to which member countries reciprocate others’ promises and contributions. Second, while the 2°C goal will likely be reached only under a very small set of conditions in any event, even temporary US withdrawal will further narrow this set significantly. Reaching this goal will then require other countries to step up their ambition at the first opportunity and to comply nearly 100% with their pledges, while maintaining high confidence in the Paris Agreement's institutions. Third, although a US withdrawal will first primarily affect the United States' own emissions, it will eventually prove even more detrimental to other countries' emissions.

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.

Aiming to reduce the number of brown (polluting) cars on the road, several countries currently promote the purchase and use of green (emission-free) cars through financial and non-financial incentives. We study how such incentives affect consumers who continue to drive brown cars. Using a simple model, we analyze the effects of policy instruments such as subsidizing green cars, taxing brown cars, and allowing green cars to drive in bus lanes. Car owners are influenced by price incentives as well as by external effects from traffic (such as congestion) both in regular lanes and in bus lanes. An extension of the model also considers how changes in local driving habits affect brown-car driving. We find that subsidizing green cars and allowing them to drive in bus lanes might increase brown-car driving. We also report the results of a recent survey containing questions specifically designed to tap the significance of the model’s core mechanisms. The results are partially consistent with propositions derived from the model. While most brown-car respondents report their driving was unchanged after the implementation of the policies to promote green cars, some – particularly in major cities – report that these policies caused them to reduce or increase their driving. We conclude that some mechanisms in our model are more important than others and that certain mechanisms appear to influence different brown-car drivers in different ways. Overall, it seems that Norwegian policies to promote the transition from brown to green cars have somewhat reduced brown-car driving.

The 2015 Paris Agreement (PA) has been widely hailed as a diplomatic triumph and a breakthrough in global climate cooperation. However, it is commonly accepted that the PA's collective goal—keeping global warming “well below” 2°C above preindustrial levels—remains ambitious. Making matters even more challenging, in 2017, global CO2 emissions resumed growth after 3 years of near standstill. In 2018, this growth accelerated. It is therefore extremely important that the PA's institutional architecture meet expectations concerning its ability to induce member countries to promise and deliver emissions reductions. This study offers a review of the rapidly growing literature on the PA, to assess its strengths and weaknesses, its significance, and its prospects. We focus on evaluations of its institutional structure and its ability to induce member countries to implement policies. We frame the issues as a trilemma: the challenge of simultaneously satisfying all three main conditions for effectiveness—broad participation, deep commitments, and satisfactory compliance rates. Based on our review, we conclude that the key challenge for the PA will likely be to facilitate sufficiently fast ratcheting‐up of nationally determined contributions, while keeping compliance rates high. This article is categorized under: Policy and Governance > Multilevel and Transnational Climate Change Governance

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.

On 1 June 2017, President Trump announced that the US intends to leave the Paris Agreement if no alternative terms acceptable to his administration can be agreed upon. In this article, an agent-based model of bottom-up climate mitigation clubs is used to derive the impact that lack of US participation may have on the membership of such clubs and their emissions coverage. We systematically analyse the prospects for climate mitigation clubs, depending on which of three conceivable roles the US takes on: as a leader (for benchmarking), as a follower (i.e. willing to join climate mitigation clubs initiated by others if this is in its best interest) or as an outsider (i.e. staying outside of any climate mitigation club no matter what). We investigate these prospects for three types of incentives for becoming a member: club goods, conditional commitments and side-payments. Our results show that lack of US leadership significantly constrains climate clubs’ potential. Lack of US willingness to follow others’ lead is an additional, but smaller constraint. Only in a few cases will US withdrawal entail widespread departures by other countries. We conclude that climate mitigation clubs can function without the participation of an important GHG emitter, given that other major emitters show leadership, although these clubs will rarely cover more than 50% of global emissions. Key policy insightsThe US switching from being a leader to being a follower substantially reduces the emissions coverage of climate mitigation clubs.The US switching from being a follower to being an outsider sometimes reduces coverage further, but has a smaller impact than the switch from leader to follower.The switch from follower to outsider only occasionally results in widespread departures by other countries; in a few instances it even entices others to join.Climate mitigation clubs can function even without the participation of the US, provided that other major emitters show leadership; however, such clubs will typically be unable to cover more than 50% of global emissions.Climate mitigation clubs may complement the Paris Agreement and can also serve as an alternative in case Paris fails. The US switching from being a leader to being a follower substantially reduces the emissions coverage of climate mitigation clubs. The US switching from being a follower to being an outsider sometimes reduces coverage further, but has a smaller impact than the switch from leader to follower. The switch from follower to outsider only occasionally results in widespread departures by other countries; in a few instances it even entices others to join. Climate mitigation clubs can function even without the participation of the US, provided that other major emitters show leadership; however, such clubs will typically be unable to cover more than 50% of global emissions. Climate mitigation clubs may complement the Paris Agreement and can also serve as an alternative in case Paris fails.

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.

This is the accepted, refereed and final manuscript to the article We study experimentally how enforcement influences public goods provision when subjects face two free-rider options that roughly parallel the nonparticipation and noncompliance options available for countries in relation to multilateral environmental agreements (MEAs). Our results add to the MEA literature in two ways. First, they suggest that compliance enforcement will fail to enhance compliance in the absence of participation enforcement. Second, they indicate that compliance enforcement will boost compliance significantly in the presence of participation enforcement. Our results also add to the experimental literature on public goods provision, again in two ways. First, they reveal that previous experimental findings of enforcement boosting cooperation are valid only in settings with forced (or enforced) participation. Second, they show that subjects’ willingness to allocate costly punishment points is significantly stronger when the enforcement system permits punishment of both types of free riding than when it permits punishment of only one type. 2, forfatterversjon

This thematic issue of Politics and Governance serves as a Festschrift in honor of Professor Dr. Philos. Arild Underdal on his 70th birthday. In this editorial, the guest editors summarize a few of Professor Underdal’s many academic merits and achievements. They also provide a synopsis of each of the ten contributions to the Festschrift, which focuses on climate governance in general and the 2015 Paris Agreement in particular.

"The 2015 Paris Agreement was widely greeted with enthusiasm. We assess the short-term and long-term potential effectiveness of Paris. Concerning short-term effectiveness, we contend that while Paris scores high on participation, and reasonably high on the depth of the parties' commitments (ambition), its Achilles' heel will likely be compliance. Concerning long-term effectiveness, we argue that Paris does little to restructure states’ incentives so as to avoid free riding. At worst, it might end up as a failure, much like Kyoto did. On the other hand, domestic and international norms could continue to develop in a direction that makes it more and more difficult for individuals, firms, and states alike to ignore the plea to limit and reduce their carbon footprints. Technological progress that gradually reduces abatement costs, combined with leadership by major emitters such as the United States, might further strengthen climate cooperation and enhance other countries' willingness to follow through. However, deep political polarization continues to represent a significant barrier to U.S. leadership on climate change." (author's abstract)

Can a conditional commitment by a major actor (for example, the European Union) induce other major actors (such as the USA, China, India, or Japan) to do more to mitigate global climate change? We analyse this question by first estimating the impact of emission reductions by one of these actors on the mitigation costs of the others and, second, by exploring how domestic politics influence the willingness of the European Union and the USA to contribute. We find that an emission cut by any actor will reduce mitigation costs for all the others and thereby expand the settlement range. These cost reductions seem, however, insufficient to induce significant unilateral policy change. Emissions trading can cut aggregate costs further, but also redistribute wealth. Domestic politics tend to add weight to the concerns of powerful actors that stand to lose from more ambitious mitigation policies.

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.

As a quintessential long-term policy problem, climate change poses two major challenges. The first is to develop, under considerable uncertainty, a plan for allocating resources over time to achieve an effective policy response. The second is to implement this plan, once arrived at, consistently over time. We consider the second of these two challenges, arguing that it consists of three interrelated, commitment problems—the time inconsistency problem, the domestic politics problem, and the anarchy problem. We discuss each of these commitment problems in some detail, explore how they relate to climate policy, and suggest institutional designs that may help limit their adverse impact. While each of these commitment problems is difficult to tackle on its own, climate change requires us to cope with all of them at once. This is likely one major reason why we have so far made only modest headway on this vital issue.

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.

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.

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.

One of the ways to induce compliance is for an international enforcement mechanism to authorize the use of punitive consequences against a non-compliant country. However, such consequences should not cause significant damage to other (compliant) countries. The compliance mechanism of the Kyoto Protocol fails to meet this requirement. The Enforcement Branch of the Compliance Committee is instructed to impose punitive consequences on a non-compliant country that will have considerable adverse welfare effects for compliant countries as well. Using a numerical model, we show that in the case of Norway, the welfare effects can actually be worse if another country is punished than if Norway itself is punished.

Arild Underdal's work on the Law of the Least Ambitious Program (LLAP) is a significant contribution to our understanding of the logic of international collaboration. The LLAP, however, applies only under particular conditions. After comparing the law to the joint decision trap and the veto player concept, we discuss four observations that tend to limit the law's domain. First, while the LLAP is intended to apply to decision-making under unanimity, in a number of international bodies decisions are made by some kind of majority voting. Second, the LLAP assumes that the alternative to collective agreement is individual decision-making, yet in practice the relevant alternative (the “reversion rule”) is often the continuation of some pre-existing collaborative arrangement. Third, whereas the LLAP assumes that the unanimity rule invariably favors the least ambitious program, there are interesting cases where this assumption does not hold. Finally, the LLAP does not take into account that the outcome of international decision-making not only depends on the decision rule and the reversion rule, but also on the voting sequence.

The Marrakesh Accords provide a detailed compliance system for the Kyoto Protocol. An innovative feature of this system is an Enforcement Branch authorized to apply punitive measures or “consequences” in the second commitment period to Annex I Parties that have been found to be in non-compliance in the first commitment period. However, even after the latest Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC), COP-11, and the first COP serving as the meeting of the Parties to the Kyoto Protocol, COP/MOP-1, it is not yet clear whether these consequences will be legally binding. The purpose of this paper is three-fold. First, we examine the legal nature of the punitive consequences embedded in the Marrakesh Accords. Second, we discuss potential motives for making these consequences legally binding. We point out that one such motive is that their implementation requires cooperation by the Party that is in non-compliance. In this regard, Kyotoȁ9s compliance system differs from other international compliance systems equipped with punitive consequences, such as those of the WTO and the UN. Finally, we consider whether making the punitive consequences legally binding is likely to make a difference. The conclusion, which should be of interest to both academic researchers and the policy community, is that the legal status of the consequences is likely to have only a modest effect on compliance levels. A country that deliberately fails to abide by other legally binding commitments under the Kyoto Protocol is also likely to resist the application of punitive consequences, regardless of whether these consequences are made legally binding or not.

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.

While there is a vast literature both on international bargaining and on how international agreements can be enforced, very little work has been done on how bargaining and enforcement interact. An important exception is Fearon (1998), who models international cooperation as a two-stage process, in which the bargaining process is constrained by a need for decentralized enforcement (meaning that the agreement must be enforced by the parties themselves, rather than a third party such as a court). Using the Clean Development Mechanism of the Kyoto Protocol as an example, the present paper proposes a different model of this kind of interaction. This model follows Fearon's in so far as we both use the infinitely repeated Prisoners' Dilemma to capture the enforcement phase of the game. However, while Fearon depicts the bargaining stage as a War of Attrition, the present model sees that stage as a sequential bargaining game of the Ståhl-Rubinstein type. The implications of the present model are compared both to those of the Ståhl-Rubenstein model and to those of the Fearon model. A surprising conclusion is that a need for decentralized enforcement tends to make the bargaining outcome more symmetrical than otherwise. Thus, the impact of bargaining power is actually smaller when the resulting agreement must be enforced by the parties themselves, than it is if enforcement is taken care of by a third party.

Using a repeated-game model, we demonstrate that by limiting the punishment for non-compliance, a climate agreement with full participation can be sustained as a weakly renegotiation-proof equilibrium even without watering down abatement levels.

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.

Fromourpoint of view, the exchange has been very rewarding. In this rejoinder, we brie‘ ysummarize our own position and identify some remaining issues where ourviews seem to differ from Oran Young’ s.First, we are encouraged by Young’ s evaluation that there are some attrac-tive features about the Oslo-Potsdam solution— in particular that it offers a con-ceptual framework producing a single effectiveness score bounded between 0and 1 which permits comparisons across regimes.Second, Young is correct in pointing out that there are multiple alternativeprocedures for evaluating regime

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.

Whereas the US President signed the Kyoto Protocol, the failure of the US Congress to ratify it seriously hampered subsequent international climate cooperation. This recent US trend, of signing environmental treaties but failing to ratify them, could thwart attempts to come to a future climate agreement. Two complementary explanations of this trend are proposed. First, the political system of the US has distinct institutional features that make it difficult for presidents to predict whether the Senate will give its advice and consent to multilateral environmental agreements (MEAs) and whether Congress will pass the required enabling legislation. Second, elected for a fixed term, US presidents might benefit politically from supporting MEAs even when knowing that legislative support is not forthcoming. Four policy implications are explored, concerning the scope for unilateral presidential action, the potential for bipartisan congressional support, the effectiveness of a treaty without the US, and the prospects for a deep, new climate treaty. Policy relevance Why does the failure of US ratification of multilateral environmental treaties occur? This article analyses the domestic political mechanisms involved in cases of failed US ratification. US non-participation in global environmental institutions often has serious ramifications. For example, it sharply limited Kyoto's effectiveness and seriously hampered international climate negotiations for years. Although at COP 17 in Durban the parties agreed to negotiate a new agreement by 2015, a new global climate treaty may well trigger a situation resembling the one President Clinton faced in 1997 when he signed Kyoto but never obtained support for it in the Senate. US failure to ratify could thwart future climate agreements.

We provide experimental evidence of self-serving fairness ideals in a dictator game. Our design includes treatments where funds can be transferred in two ways to the one player and in one way to the other. Two methods for transferring funds to the recipient produce generosity levels similar to those of the regular dictator game. However, two methods for transferring funds to the dictator reduce her generosity substantially. Hence, the fairness ideal adopted by dictators appears to be equal share per individual in the former case (as in the regular dictator game), and equal share per transfer method in the latter case.