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Abstract:
This article provides a non-technical overview of important results of the game theoretical literature on the formation and stability of international environmental agreements (IEAs) on transboundary pollution control. It starts out by sketching features of first and second best solutions to the problem of transboundary pollution. It then argues that most actual IEAs can be considered at best as third best solutions. Therefore, three questions are raised: 1) Why is there a difference between actual IEAs and first and second best solutions? 2) Which factors determine this difference? 3) Which measures can help to narrow this difference? This article attempts to answer these questions after giving an informal introduction to coalition models.

International pollution, International environmental agreements, Treaty design, Coalition theory

Abstract:
We extend the work on coalition formation in global pollution control by allowing for multiple coalitions. Equilibrium coalitions are derived under different "rules of the game" and compared with each other. We consider internal & external equilibria and equilibrium binding agreements in the cartel formation game, coalition-proof and strong Nash equilibria in the open-membership game and in the exclusive membership - and - games, subgame-perfect equilibria in the sequential move unanimity game and equilibria in the equilibrium binding agreement game. We show that farsightedness and exclusive membership leads to more concentrated coalition structure, implying lower global emissions and higher global welfare. Moreover, we evaluate the different coalition formation games with respect to their ability to explain existing international environmental agreements and with respect to their theoretical consistency.

International environmental agreements, coalition formation games, global pollution

Abstract:
We analyze with an integrated assessment model of climate change the formation of international environmental agreements (IEAs) by applying the widely used concept of internal & external stability and several modifications of it. We relax the assumptions of a single agreement and open membership rule. It turns out that regional agreements are superior to a single agreement and exclusive is superior to open membership in welfare and ecological terms. Moreover, we show the importance of transfers for successful treaty-making. We relate our results to the design of current and past IEAs as well as to other issues of international policy coordination.

Design of climate treaty protocol, Coalition formation, Non-cooperative game theory

Abstract:
We empirically test stability of climate change coalitions with the STAbility of Coalitions model (STACO). The model comprises twelve world regions and captures important dynamic aspects of the climate change problem. We apply the stability concept of internal and external stability to a cartel formation game. It is shown that only if benefits from global abatement are sufficiently high, stable coalitions emerge, though they only marginally improve upon the Nash equilibrium. We explain this phenomenon by analyzing the individual incentive structure of all regions and relate our results to the predictions of theory.
Kyoto-Protocol, Cartel formation game, Non-cooperative game theory

International environmental agreements,

Abstract:
We combine the newest concepts o non-cooperative coalition theory with a computable general equilibrium model close to the seminal RICE-model of Nordhaus and Yang (1996) to determine stable coalition structures in a global warming game. We consider three coalition games that allow for the formation of multiple coalitions. The coalition games represent different designs of climate treaty protocols. Counterintuitively, it turns out that treaties based on a unanimous decision rule and exclusive membership lead to superior outcomes than treaties with open membership. We also demonstrate that if coalition formation is not restricted to a single coalition, as this has been done previously in the literature, coalition structures with multiple coalitions will emerge in equilibrium. Most of the regional agreements are superior to single agreements. Moreover, our findings confirmthose derived fromsim pler theoretical models that a cleverly designed transfer scheme can foster cooperation and that fromthe number of participants the success of a treaty cannot be inferred. They also support a conjecture of theory that in the case of greenhouse gases stable coalition structures (partial cooperation) can close the gap between the global optimum (full cooperation) and the Nash equilibrium(no cooperation) by a substantial amount

design of climate treaty protocol, coalition formation, non-cooperative game theory

Abstract:
The literature on international environmental agreements has recognized the role transfers play in encouraging participation in international environmental agreements (IEAs), but the few results achieved so far are overly specific and do not exploit the full potential of transfers for successful treaty-making. Therefore, in this paper, we develop a framework that enables us to study the role of transfers in a more systematic way. We propose a design for transfers using both internal and external financial resources and making 'welfare optimal agreements' self-enforcing. To illustrate the relevance of our transfer scheme for actual treaty-making, we use a well-known integrated assessment model of climate change to show how appropriate transfers may be able to induce almost all countries into signing a self-enforcing climate treaty.

Self-enforcing international environmental agreements, climate policy, transfers, international environmental agreements

Abstract:
Transfers often play a crucial role in encouraging participation in international environmental agreements (IEAs). However, the economic literature on transfers is very limited and results achieved so far do not exploit the full potential of transfers for successful treaty-making. Therefore, in this paper, we develop a framework that enables us to study the role of transfers in a more systematic way. We propose a design for transfers using both internal and external financial resources and making welfare optimal agreements self-enforcing. To illustrate the relevance of our transfer scheme for actual treaty-making, we use a well-known integrated assessment model of climate change to show how appropriate transfers may be able to induce almost all countries into signing a self-enforcing climate treaty.

Self-enforcing international environmental agreements, Climate policy, Transfers

Abstract:
This paper analyses stability of coalitions for greenhouse gas abatement under different sharing rules applied to the gains from cooperation. We use a 12-region model to examine internal and external stability of coalitions. We determine and compare stable coalitions under different surplus sharing rules; for example, grandfathering (sharing proportional to current emissions) and a number of equitable rules, i.e. sharing according to historical responsibilities for past emissions. Due to strong free-rider incentives we find only small stable coalitions for all sharing rules examined. We observe that stable coalitions consist of regions with low marginal abatement costs that are attractive partners in any coalition and regions receiving the highest shares of the surplus from cooperation under a particular sharing rule. We find that equitable rules may not be conducive to success: in fact, a grandfathering scheme leads to the most successful coalition in terms of global abatement and global welfare.

Abstract:
This paper analyses stability of coalitions for greenhouse gas abatement for different sharing rules applied to the gains from co-operation. We use a 12-regions model designed to examine internal and external stability of coalitions (STACO). We compare different sharing rules like, for example, grandfathering (i.e. sharing proportional to emissions) and a number of so-called equitable rules like, for example, sharing proportional to population or according to historical responsibilities. Due to strong free-rider incentives we find only small stable coalitions for all sharing rules examined. As a general pattern we observe that coalitions consist of regions with low marginal abatement costs, which are attractive partners in any coalition, and regions which have the highest claims according to the respective sharing rule. Furthermore, we find that a grandfathering scheme leads to the largest and - in terms of greenhouse gas abatement - most successful coalition, while many of the equitable rules achieve very little.

International environmental agreements, Sharing rules, Stability of coalitions

Abstract:
This paper compares stability of international environmental agreements for six different rules of coalition formation under very general conditions (any type of heterogeneity between countries). The rules can be interpreted as different institutional settings in which treaty formations take place and/or different designs of agreements. We consider open and restricted open membership game as well as four exclusive membership games with different degrees of unanimity required to form coalitions. From a policy perspective, counterintuitively, it turns out that stability is higher under exclusive than under open membership and stability increases with the degree of unanimity. We discuss the policy implications of our result for future treaty-making.

Non-cooperative game theory, Rules of coalition formation, Stability

Abstract:
We identify the core as an appealing stability concept of cooperative game theory, but argue that the non-cooperative approach has conceptual advantages in the context of economic problems with externalities. Therefore, we derive a non-cooperative foundation of core-stability for positive externality NTU-games. First, in the spirit of Hart/Kurz (1983), we develop a game that we call - game and show that strong Nash equilibria coalition structures in this game are identical to - and - core stable coalition structures. Second, as a by-product of the definition of the - game, we develop an extension called an - game. Finally, we compare equilibria in the - and - game with those in the - and - game of Hart and Kurz (1983).We identify the core as an appealing stability concept of cooperative game theory, but argue that the non-cooperative approach has conceptual advantages in the context of economic problems with externalities.

Core-stability, Non-cooperative Game Theory, Positive Externality Games

Abstract:
We propose a class of sharing schemes for the distribution of the gains from cooperation for coalition games with externalities. In the context of the partition function, it is shown that any member of this class of sharing schemes leads to the same set of stable coalitions in the sense of d'Aspremont et al. (1983). These schemes are "almost ideal" in that they stabilize these coalitions which generate the highest global welfare among the set of "potentially stable coalitions." Our sharing scheme is particularly powerful for economic problems that are characterized by positive externalities from coalition formation and which therefore are likely to suffer from severe free-riding.

Coalition games, Partition function, Externalities, Sharing schemes

Abstract:
Results derived from empirical analyses on the stability of climate coalitions are usually very sensitive to the large uncertainties associated with the benefits and costs of climate policies. This paper provides the methodology of Stability Likelihood that links uncertainty about benefits and costs of climate change to the stability analysis of coalitions in a stochastic, empirical setting. We show that the concept of Stability Likelihood improves upon the robustness and interpretation of stability analysis. Our numerical application is based on a modified version of the climate model STACO. It turns out that the only non-trivial coalition structure with a relatively high Stability Likelihood (around 25 percent) is a coalition between the European Union and Japan, though quantitative results depend especially on the variance in regional benefits from abatement.

Climate change, Coalition formation, International environmental agreements, Uncertainty

Abstract:
We analyze the formation of self-enforcing international environmental agreements under the assumption that countries announce their participation either simultaneously or sequentially. It is shown that a sequential formation process opens up possibilities for strategic behavior of countries that may lead to inferior outcomes in terms of global abatement and welfare. We then analyze whether and under which conditions a regulator like an international organization, even without enforcement power, can improve upon globally suboptimal outcomes through coordination and moderation, given that recommendations must be Pareto-improving to all parties.

International environmental agreements, Timing of participation decision

Abstract:
According to international law, straddling fish stocks should preferably be managed cooperatively through regional fisheries management organizations (RFMOs). This paper analyzes the stability and success of these organizations through a game in partition function form based on the classical Gordon-Schaefer bioeconomic model. A comprehensive analysis of the economic and biological fundamentals that influence the success of coalition formation is provided. The results show that the larger the number of fishing states that compete for the fish stock the higher would be the relative gains from full cooperation, but the lower is the likelihood of large RFMOs being stable. It is also shown that the success of coalition formation is positively correlated with the degree of production cost asymmetry among fishing states and negatively with the overall level of efficiency.

Straddling Fish Stock, Regional Fisheries Management Organizations, Unregulated Fishing, Bioeconomic Model, Coalition Formation Model, Free-Riding

Abstract:
Standard non-cooperative game theoretical models of international environmental agreements (IEAs) draw a pessimistic picture of the prospective of successful cooperation: only small coalitions are stable that achieve only little. However, there also exist IEAs with higher participation and more success. In order to explain this phenomenon, this paper departs from the standard assumption of joint welfare maximization of coalition members, implying ambitious abatement targets and strong free-riding. Instead, it considers that countries agree on modest emission reduction targets. This may sufficiently raise participation so that the success of treaties improves in terms of global emission reduction and global welfare. Thus, modesty may pay, though the first best optimum cannot be achieved.

International environmental agreements, Internal&external stability, Modest emission reduction

Abstract:
We provide an existence and a uniqueness result for coalitional equilibria of a game in strategic form. Both results are illustrated for a public good game and a homogeneous Cournot-oligopoly game.

Existence and uniqueness of coalitional equilibrium, Game in strategic form

Abstract:
Several studies found ancillary benefits of environmental policy to be of considerable size. These additional private benefits imply not only higher cooperative but also noncooperative abatement targets. However, beyond these largely undisputed important quantitative effects, there are qualitative and strategic implications associated with ancillary benefits: climate policy is no longer a pure but an impure public good. In this paper, we investigate these implications in a setting of non-cooperative coalition formation. In particular, we address the following questions. 1) Do ancillary benefits increase participation in international environmental agreements? 2) Do ancillary benefits raise the success of these treaties in welfare terms?

Ancillary Benefits, Climate Policy, Coalition Formation, Game Theory, Impure Public Goods

Abstract:
In this paper we study the effect of different treaty designs on the success of international environmental agreements (IEAs). We analyze the standard assumption of an efficient abatement scheme and three uniform abatement quota schemes. Apart from analytical results, the analysis is supported by simulations based on the STACO (stability of coalitions) model. It turns out that quota agreements where the members decide by majority or unanimity voting are successful in overcoming free-rider incentives within an IEA. Finally, our results provide a rationale for the application of uniform abatement quotas in IEAs.

Abstract:
We analyze the implication of different allocation schemes of CO2-emission permits for stability and the success of international climate agreements. Our model combines a game theoretical with an empirical module that comprises 12 world regions and captures important dynamic aspects of the climate change problem. We consider seven different permit allocation schemes. Two "pragmatic schemes" allocate permits according to a uniform emission reduction quota, five "equitable schemes" allocate permits based on some normative criteria frequently discussed in the literature permit trading can raise participation and the success of climate agreements, but pragmatic schemes are superior to equitable ones.

climate agreements, tradable emission permits, coalition formation, self-enforcing agreements