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Currently living people might reduce carbon emissions to protect themselves, their wealth, or future generations from climate damage. An overlapping generations climate model with endogenous asset priceand investment levels disentangles these incentives. Asset markets capitalize the future e¤ects of policy, regardless of people�s concern for future generations. These markets can lead self-interested agents to undertake signi�cant abatement. A small climate policy that raises the price of capital increases welfare of old agents and also increases welfare of young agents with a high intertemporal elasticity of sub-stitution. Climate policy can also have subtle distributional e¤ects across the currently living generations.

We modify a canonical participation game used to study International Environmental Agreements (IEA), considering both mixed and pure strategies at the participation stage, and including a prior cost-reducing investment stage. The use of mixed strategies at the participation stage reverses a familiar result and alsoreverses the policy implication of that result: with mixed strategies, equilibriumparticipation and welfare is higher in equilibria that involve higher investment.

A two-sector OLG model illuminates previously unexamined intergenerationaleffects of a tax that protects an environmental stock. A traded asset capitalizes the economic returns to future tax-induced environmental improvements, benefiting the current asset owners, the old generation. Absent a transfer, the tax harms the young generation by decreasing their real wage. Future generations benefit fromthe tax-induced improvement in environmental stock. The principalintergenerational conflict arising from public policy is between generationsalive at the time society imposes the policy, not between generations alive at different times. A Pareto-improving policy can be implemented under various political economy settings.

We explain how the structure of multi-national or multi-regional environmental agreements affect their chance of success. Trade in emissions permits has ambiguous and in some cases surprising effects on both the equilibrium level of abatement, and on the ability to persuade nations or regions to participate in environmental agreements. An escape clause policy and a safety valve policy have essentially the same properties when membership in environmental agreement is pre-determined, but they create markedly different effects on the incentives to join such an agreement. The two policies lead to a qualitative difference in the leverage that a potential member of the agreement exercises on other members.

We examine the size of stable coalitions in a participation game that has been used to model international environmental agreements, cartel formation, R&D spillovers, and monetary policy. The literature to date has relied on parametric examples; based onthese examples, a consensus has emerged that in this kind of game, the equilibrium coalition size is small, except possibly when the potential benefits of cooperation are also small. In this paper, we develop a non-parametric approach to the problem, and demonstrate that the conventional wisdom is not robust. In a general setting, we identify conditions under which the equilibrium coalition size can be large even when potential gains are large. Contrary to previously examined leading special cases, we show that reductions in marginal abatementcosts in an international environmental game can increase equilibrium membership, and we provide a measure of the smallest reduction in costs needed to support a coalition of arbitrary size.

This paper studies the reality and the potential for green industrial policy. We provide a summary of the green industrial policies, broadly understood, for five countries. We then consider the relation between green industrial policies and trade disputes, emphasizing theBrazil-US dispute involving ethanol and the broader US-China dispute. The theory of public policy provides many lessons for green industrial policy. We select four of these lessons, involving the Green Paradox, the choice of quantities versus prices with endogenous investment, the coordination issues arising from emissions control, and theability of green industrial policies to promote cooperation in reducing a global public bad like carbon emissions.

Apple’s original decision to market iPhones using a single downstream vendor prompted calls for mandatory universal distribution (MUD), whereby all downstream vendors would sell the iPhone under the same contract terms. The upstream monopoly may want eitherone or more downstream vendors, and, in either case, consumer welfare may be higher with either one or more firms. If the income elasticity of demand for the new good is greater than the income elasticity of the existing generic good, the MUD requirements leads to a higherequilibrium price for both the new good and the generic, and therefore lowers consumer welfare.

We imbed a classic fishery model, where the optimal policy follows a Most Rapid Approach Path to a steady state, into an overlapping generations setting. The current generation discounts future generations’ utility flows at a rate possibly different from the pure rate of time preference used to discount their own utility flows. The resulting model has non-constant discount rates, leading totime inconsistency. The unique Markov Perfect equilibrium to this model hasa striking feature: provided that the current generation has some concern forthe not-yet born, the equilibrium policy does not depend on the degree of thatconcern.

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I provide a selective review of discounting and climate policy. After reviewing evidence on the importance of the discount rate in setting policy, I ask whether standard models tend to exaggerate the sacrifices that the current generation needs to undertake in order to internalize climate damages. I then consider whether the risk of catastrophic damage really overwhelms discounting, in the determination of optimal policy. I revisit the question of how we actually think about the distant future.

We provide a unified discussion of the issues that confront negotiators of the next international climate agreement. We offer a novel proposal that entitles countries to discharge their treaty obligations by paying a “fine”. This escape clause provides cost insurance, simplifies the problem of enforcing compliance, and increases incentives to participate in the agreement. We explain why developed country obligations should rely on a cap and trade commitment rather than carbon taxes. A Central Bank maintains stability of carbon prices by defending a price ceiling and floor. An so-called intensity target is not a good alternative to an emissions cap. Modest trade restrictions, consistent with WTO law, will form an important part of the next agreement. Developed and developing countries have differentiated responsibilities. Developing countries do not adopt binding targets at the next round of negotiations, but they accept the principle of binding targets in the subsequent agreement, beginning in the early 2020s. Developed country participation relies on a reformed CDM and sectoral agreements that are financed by the sale of emissions permits.

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Disagreement over the form of regulation of greenhouse gasses motivates a comparison of market based and command and control policies. More efficient policies can increase aggregate marginal abatement cost, resulting in higher emissions. Multiple investment equilibria and “regulatory uncertainty” arise when firms anticipate command and control policies. Market based policies eliminate this uncertainty. Command and control policies cause firms to imitate other firms’ investment decisions, leading to similar costs and small potential efficiency gains from trade. Market based policies induce firms to make different investment decisions, leading to different costs and large gains from trade. We imbed the regulatory problem in a “global game” and show that the unique equilibrium to that game is constrained socially optimal.

Non-strategic firms with rational expectations make investment and emissions decisions. The investment rule depends on firms’ beliefs about future emissions policies. We compare emissions taxes and quotas when the (strategic) regulator and (nonstrategic) firms have asymmetric information about abatement costs, and all agents use Markov Perfect decision rules. Emissions taxes create a secondary distortion at the investment stage, unless a particular condition holds; emissions quotas do not create a secondary distortion. We solve a linear-quadratic model calibrated to represent the problem of controlling greenhouse gasses. The endogeneity of abatement capital favors taxes, and it increases abatement.

The tendency to foreshorten time units as we peer further into the future provides an explanation for hyperbolic discounting at an intergenerational time scale. We study implications of hyperbolic discounting for climate change policy, when the probability of a climate-induced catastrophe depends on the stock of greenhouse gasses. We provide a positive analysis by characterizing the set of Markov perfect equilibria (MPE) of the intergenerational game amongst a succession of policymakers. Each policymaker reflects her generation’s preferences, including its hyperbolic discounting. For a binary action game, we compare the MPE set to a “restricted commitment” benchmark. We compare the associated “constant equivalent discount rates” and the willingness to pay to control climate change with assumptions and recommendations in the Stern Review on Climate Change.“. . .My picture of the world is drawn in perspective. . . I apply my perspective not merely to space but also to time” —Ramsey.

The successor to the Kyoto Protocol should impose national ceilings on rich countries’ greenhouse gas emissions and promote voluntary abatement by developing countries. Our proposal gives signatories the option of exercising an escape clause that relaxes their requirement to abate. This feature helps to solve the participation and compliance problems that have weakened the Protocol. We support the use of carefully circumscribed trade restrictions in order to reduce the real or perceived problem of carbon leakage.

In customary international and public law, “takings” resulting from regulations designed to protect the public good are generally excluded from compensation rules; this exclusion is known as a police powers carve-out (PPCO). Increasingly, this PPCO is being challenged, particularly in international investment law. This paper analyzes the efficiency properties of a PPCO in a model with endogenous regulation, investment and entry. We design a one-parameter family of carve-out/compensation schemes that induce efficient regulation and firm level investment even when the regulator suffers fiscal illusion and the social benefit from regulation is private information to the regulator. We show that offering a carve-out reduces the subsidy to risky industry implicit in compensation rules; thus, a carve-out can mitigate the entry problem.

A constant social discount rate cannot reflect both a reasonable opportunity cost of public funds and an ethically defensible concern for generations in the distant future. We use a model of hyperbolic discounting that achieves both goals. We imbed this discounting model in a simple climate change model to calculate “constant equivalent discount rates” and plausible levels of expenditure to control climate change. We compare these results to discounting assumptions and policy recommendations in the Stern Review on Climate Change.

A reform to the Kyoto Protocol that allows signatories to pay a fine instead of meeting the target level of abatement would achieve three goals. First, it would defuse one U.S. objection to the agreement: the concern that the cost of achieving the target might turn out to be extremely high. Second, unlike other cost-reducing measures (such as trade in pollution permits) it would increase the equilibrium number of signatories in a non-cooperative participation game. Third, it would make it easier to force signatories to comply with their obligations. We study the participation game under an escape clause using both a Nash Equilibrium and the concept of a stable set when nations are “farsighted”. We compare our results to a prominent model of International Environmental Agreements (IEAs) which finds that the equilibrium size of an IEA tends to be small when the benefits of cooperation are large. We show that with an escape clause and a properly chosen level of fine, a large IEA can be formed even when the benefits of cooperation are large.

Low probability catastrophic climate change can have a significant influence on policy under hyperbolic discounting. We compare the set of Markov Perfect Equilibria (MPE) to the optimal policy under time-consistent commitment. For some initial levels of risk there are multiple MPE; these may involve either excessive or insufficient stabilization effort. These results imply that even if the free-rider problem amongst contemporaneous decision-makers were solved, there may remain a coordination problem amongst successive generations of decision-makers. A numerical example shows that under plausible conditions society should respond vigorously to the threat of climate change.

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The possibility of non-constant discounting is important in environmental and resource management problems where current decisions affect welfare in the far-distant future, as with climate change. The difficulty of analyzing models with non-constant discounting limits their application. We describe and provide software to implement an algorithm to numerically obtain a Markov Perfect Equilibrium for an optimal control problem with non-constant discounting. The software is available online. We illustrate the approach by studying welfare and observational equivalence for a particular renewable resource management problem.

We study a model in which the level of environmental regulation depends on abatement cost, which depend on aggregate levels of investment in abatement capital. Firms are non-strategic. When emissions quotas are not tradable, there are multiple competitive equilibria to the investment problem. Allowing trade in permits leads to a unique socially optimal equilibrium. For a given distribution of investment, allowing trade in permits has an ambiguous effect on the optimal level of regulation. Previous results on coordination games with non-atomic agents are applied to the problem of environmental regulation with endogenous investment in abatement capital.

NAFTA’s investment treaty has led to several expropriation compensation claims from investors hurt by new environmental regulations. Expropriation clauses in international treaties solve post-investment moral hazard problems such as hold-ups. However, these clauses can interact with National Treatment clauses in a manner that hinders investment. A police powers carve-out from the definition of expropriation can be Pareto-improving and can increase the level of foreign investment.

Recent papers show that imperfect property rights to a natural resource - a sector-specific factor - can be a source of comparative advantage. In these models, weaker property rights attract labor - the only mobile factor - to the resource sector, increasing the country's comparative advantage for that sector. If capital in addition to labor is mobile, and if the benefits of capital are non-excludable or if the degree of property rights is endogenous, a deterioration of property rights has ambiguous effects on comparative advantage and on the equilibrium wage/rental ratio. (c) 2005 Elsevier B.V. All rights reserved.

If a regulator is unable to measure firms' individual emissions, an ambient tax can be used to achieve the socially desired level of pollution. With this tax, each firm pays a unit tax on aggregate emissions. In order for the tax to be effective, firms must recognize that their decisions affect aggregate emissions. When firms behave strategically with respect to the tax-setting regulator, under plausible circumstances their tax burden is lower under an ambient tax, relative to the tax which charges firms on the basis of individual emissions. Firms may prefer the case where the regulator is unable to observe individual firm emissions, even if this asymmetric information causes the regulator to tax each firm on the basis of aggregate emissions.

In familiar models, a decrease in the friction facing mobile factors (e.g., lowering their adjustment costs) increases a coordination problem, leading to more circumstances where there are multiple equilibria. We show that a decrease in friction can decrease coordination problems if, for example, a production externality arises from a changing stock of knowledge or a changing environmental stock. In general, the relation between the amount of friction that mobile factors face and the likelihood of multiple equilibria is non-monotonic.

The use of a constant discount rate to study long-lived environmental problems such as global warming has two disadvantages: the prescribed policy is sensitive to the discount rate, and with moderate discount rates, large future damages have almost no effect on current decisions. Time-consistent quasi-hyperbolic discounting alleviates both of these modeling problems, and is a plausible description of how people think about the future. We analyze the time-consistent Markov Perfect equilibrium in a general model with a stock pollutant. The solution to the linear-quadratic specialization illustrates the role of hyperbolic discounting in a model of global warming. (C) 2004 Elsevier B.V. All rights reserved.

This note derives the dynamic programming equation (DPE) to a differentiable Markov Perfect equilibrium in a problem with non-constant discounting and general functional forms. Beginning with a discrete stage model and taking the limit as the length of the stage goes to 0 leads to the DPE corresponding to the continuous time problem. The note discusses the multiplicity of equilibria under non-constant discounting, calculates the bounds of the set of candidate steady states, and Pareto ranks the equilibria.

The use of a constant discount rate to study long-lived environmental problems such as global warming has two disadvantages: the prescribed policy is sensitive to the discount rate, and with moderate discount rates, large future damages have almost no effect on current decisions. Time-consistent quasi-hyperbolic discounting alleviates both of these modeling problems, and is a plausible description of how people think about the future. We analyze the time-consistent Markov Perfect equilibrium in a general model with a stock pollutant. The solution to the linear-quadratic specialization illustrates the role of hyperbolic discounting in a model of global warming.

Recent papers show that imperfect property rights to a natural resource--a sector-specific factor--can be a source of comparative advantage. in these models, weaker property rights attract labor--the only mobile factor--to the resource sector, increasing the country's comparative advantage for that sector. If capital in addition to labor is mobile, and if the benefits of capital are non-excludable or if the degree of property rights is endogenous, a deterioration of property rights has ambiguous effects on comparative advantage and on the equilibrium wage-rental ratio.