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Eric A. Posner and David Weisbach, Climate Change Justice

J. Paul Kelleher
p. 331-336
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Eric A. Posner and David Weisbach, Climate Change Justice, Princeton: Princeton University Press, 2015, 232 pages, ISBN 978-069116666-7

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Crédits : Princeton University Press

1 Even when this book was first published in 2010, there was a large literature on the nature of climate change justice. (The 2015 paperback release that occasioned this review makes no changes to the 2010 text.) Of course not all of the climate justice literature to that date was penned by philosophers, but a great of it was and naturally philosophers claim to have much to say about climate justice. So it is somewhat surprising how infrequently Eric Poser and David Weisbach engage with the philosophical literature in Climate Change Justice. To be sure, Peter Singer’s climate change chapter in One World is referred to a few times, as is Martha Nussbaum’s Frontiers of Justice, although the latter (so far as I can tell) never mentions climate justice or global warming. Several other key works on climate justice are referenced in the book’s first footnote, but then are never mentioned again. So this is certainly not a book about theories of climate change justice.

2 It is also not a book that offers its own theory of climate change justice. As Posner and Weisbach explain, they aim to stay theoretically “ecumenical” (173) while defending the supreme importance of a dictum that is “not an ethical principle but pragmatic constraint” (6). They label this constraint International Paretianism (IP). The most important climate change duty, according to Posner and Weisbach, concerns the establishment of a binding and effective emissions-reducing treaty, and IP states that “all nations must believe themselves better off by their lights as a result of [any] climate treaty” (6). Posner and Weisbach have strong views about what sort of treaty could satisfy IP, and I will come to these presently. But I think it is fair to say that this book’s main concern with climate change justice is its concern to argue that certain “influential claims about climate change justice are both vulnerable in principle and dangerous in practice” (190).

3 I am not sure that all of Posner and Weisbach’s targeted claims were ever that influential to begin with. Consider the first such claim, which Posner and Weisbach take up in chapter 4, the first of what they call the book’s “core” chapters. (Chapter 1 usefully covers the scientific facts, at least as they were understood in 2010; chapter 2 explains the similarities and differences between carbon taxes and cap-and-trade arrangements; and chapter 3 offers a discouraging appraisal of international negotiations up to that point in time.) Chapter 4 engages with the question of “whether rich nations have a special obligation to deal with climate change, not because they are principally responsible, but simply because they are rich” (73). This question is presented by Posner and Weisbach as equivalent to question of whether a climate treaty is the best vehicle to effect independently desirable redistribution from rich nations to poor nations. But aren’t these two very different questions? One can believe that a climate treaty should be narrowly focused on the climate question—and not on the much broader distributive justice question—and yet also believe that when it comes to climate, rich nations should bear the largest burden because they are best able to do so. And yet by devoting almost all of their energy to arguing that a climate treaty is a bad way to promote overall distributive justice, Posner and Weisbach largely neglect the significant climate justice literature that defends the much more plausible “ability to pay” stance on the climate question. When they do briefly entertain the proposition that rich nations should lead on climate change to avoid “imposing crushing burdens on developing nations,” Posner and Weisbach completely duck the justice issues by writing “While we agree that distributive concerns might justify such an approach…the strong intuitions behind this approach are likely driven by other concerns. In particular…it might very well be the most efficient or optimal policy” (92). One wants to ask, “In whom are these strong intuitions ‘likely’ to be driven by non-justice concerns?” and—more importantly—“Setting aside questions of human psychology, what can be said for the idea that a just climate treaty will ask more of rich countries?”

4 By contrast with chapter 4, chapters 5 and 6 do squarely address common claims about climate justice, and here Posner and Weisbach’s discussion is much more satisfying. Chapter 5 takes up the question of whether justice requires placing heavier burdens on nations that have contributed most to the stock of greenhouse gases in the atmosphere. Posner and Weisbach note that most of the historical emitters are now dead, and that their descendants have inherited an energy regime that is very difficult to abandon quickly. They mention that some theorists respond to this point with the claim that even if individual emitters are dead, their nations are extended through time and still exist today. Posner and Weisbach have much to say in response to this, with some of the stronger points highlighting the innocence of much pre-1980s carbon-emitting activity, the difficulty of one nation addressing the climate problem all on its own (and thus the futility of transforming an energy regime when other nations were not going to), and the fact that while “past generations of Americans have imposed costs on the rest of the world, they have also conferred substantial benefits” as well (106). While there is much one might criticize in this discussion, it certainly engages with leading ideas in the climate justice literature, and contributes usefully to the issue. This is true of chapter 6 as well, where Posner and Weisbach argue against the view that a just climate treaty will give every individual in the world an equal right to emit (a certain amount of) greenhouse gasses. This “equal per capita emissions permits” view has been much discussed in the climate justice literature, and again Posner and Weisbach’s treatment is valuable. They note that “Per capita allocations also have the disadvantage of giving large numbers of permits to highly populated nations that have relatively little to lose from climate change” (134). They argue that a sensible justice perspective would allocate more emissions allowances to poor nations with much to lose from climate change, since that is a better way to even out the full package of benefits and burdens from both climate change and a climate treaty.

5 And yet even here, where Posner and Weisbach offer a substantive and plausible defense of what climate justice requires, they are quick to “acknowledge the tension between feasibility arguments and ethical arguments” (143). No treaty satisfying the pragmatic constraint of International Paretianism will reflect either Posner and Weisbach’s ethically preferred emissions allocation scheme or the principle of equal per capita allocations. So does this mean that pragmatism is the only virtue that a feasible treaty is likely to exhibit? Posner and Weisbach do not think so, for they suggest that any such treaty will also be “optimal” in the economic sense that “the treaty reduces emissions to the extent that the cost of reducing emissions a little bit more is equal to the benefit of reducing emissions a little bit more” (55). Two further claims are related to this one: first, that an optimal treaty creates a surplus that can be distributed in various ways; and second, that achieving an optimal treaty “could well require side payments to rich countries like the United States... from very poor countries which are extremely vulnerable to climate change—such as Bangladesh” (86).

6 Unfortunately, the sort of economic optimality that a feasible treaty can deliver is of very limited ethical appeal, as the dreadful image of side-payments from Bangladesh to the U.S. indicates. It is true that optimality formally involves the marginal costs of abatement equaling marginal benefits. But the substantive connection between optimality, surplus, and side-payments requires a further premise, namely that the benefits and costs of abatement are to be measured in terms of willingness to pay and willingness to accept. Only when benefits and costs are measured in this specific way will a sub-optimal emissions regime guarantee a Pareto-improving path to optimality (Kelleher, 2015). If, by contrast, the costs of climate change are measured in terms of Disability-Adjusted Life Years (DALYs), a common non-monetized measure of health deficits, then there will be no guarantee—indeed, no realistic possibility—that costs and benefits can be brought into alignment in a way that leaves all parties at least as well off as they currently are. Since measuring the costs of climate change in terms of willingness to pay is at best ethically questionable, and since Posner and Weisbach refuse to commit to any particular conception of well-being (171), the book gives no reason to think that the “optimality” of feasible treaties is of any ethical consequence beyond the mere proposition that any treaty is better than no treaty.

7 It also seems that the optimality that feasible treaties can deliver conflicts with Posner and Weisbach’s view on discounting the future, which is the subject of chapter 7. The chapter on discounting is largely adapted from a previously published paper by Weisbach and Cass Sunstein (2009). Posner and Weisbach explain in their Acknowledgements that Sunstein was to be a co-author of the book, but that he was unable to participate in later stages owing to his position in the Obama Administration. According to Posner and Weisbach, the debate over discounting pits “ethicists” against “positivists”. Ethicists complain that discounting the value of future damages (e.g. illness, disability, death) means that “we may be willing to spend only a very small amount today to prevent these serious harms in the future” (153). Posner and Weisbach use the illustrative example of climate change-induced damages totaling $1 trillion in one hundred years: “If the discount rate is 7 percent, we would be willing to spend only a little over $1 billion—one one-thousandth of the damages—to prevent that harm!” (148). Even with a much smaller discount rate than 7 percent, it might not make economic sense to spend a tiny amount now to prevent catastrophic damages in the much farther future. With the ethicists, Posner and Weisbach hold that discounting at market interest rates “can result in serious injustice and may violate our ethical obligations to the future” (154). But this cannot and must not be taken to invalidate the positivists’ main thesis, according to Posner and Weisbach. This is that opportunity costs must be considered when making both intra- and inter-temporal investment decisions. As a mathematical matter, one can determine whether an investment is the highest yielding of a set of alternatives by discounting its time series of benefits by the interest rate offered by the best alternative investment. If the numerical value of this exercise is negative, the best alternative is the best of the lot; if the numerical value is positive, the investment is superior to its best alternative. Posner and Weisbach agree with the positivists that it is irrational to ignore the importance of opportunity costs, but they disagree with real-world positivists about how opportunity costs should be taken into account. Instead of performing the standard mathematical calculation and simply choosing the investment or project whose discounted value is positive, Posner and Weisbach recommend that intertemporal priorities first be set on ethical grounds, and only then should market interests rates be used to choose the set of investments that most cheaply allocates the ethically proper amount of welfare to the various generations. On this approach, which more resembles cost-effectiveness analysis than standard cost-benefit analysis, it is conceivable that the current generation should adopt a future-oriented project whose present cost is greater than its discounted present value. Whether that is so depends on whether delivering that future benefit is one of our ethically mandated “legacies” for the future (159).

8 The ethicist/positivist distinction mirrors to some extent the “prescriptivist” / “descriptivist” distinction drawn by Kenneth Arrow et al. in a contribution to the 1995 Second Assessment Report of the Intergovernmental Panel on Climate Change. (Posner and Weisbach curiously do not refer to this prior discussion.) Arrow et al. were clear that even within a prescriptivist approach that grounds discount rate in ethical principles, opportunity costs must still be factored in indirectly, presumably by converting displaced investments into a time stream of foregone consumption, and then by treating this as a cost, rather than as a discount rate. (For more on this procedure, see Dasgupta, Sen, and Marglin (1972), chapter 14.) The only examples of “ethicists” that Posner and Weisbach cite are Nicholas Stern and Geoffrey Heal, and it is true that the works cited seem not to acknowledge Arrow et al.’s strictures. But one study that does is Cline (1992), and it would have been very useful for Posner and Weisbach to compare their own hybrid approach to Cline’s, since the latter is more in line with established cost-benefit techniques. That would also have gone some way toward explaining how the concept of optimality that plays such a prominent role in early chapters of Climate Change Justice jibes with a seemingly discordant approach to discounting in chapter 7. For it is at best opaque how the controversial views of the ethicists are to be incorporated into climate treaties that respect Posner and Weisbach’s International Paretianism.

9 Climate Change Justice is a wide-ranging book that defends plausible claims concerning the moral relevance of historical emissions and the moral status of policies granting each person in the world the same rights to emit greenhouse gases. It is also—and primarily—an ardent plea for pragmatism and strategy in the face of perhaps the most important collective action problem in history. Although the discussion is pitched in welfarist terms, the authors’ failure to defend a particular conception of well-being, and their silence on the tensions between ethical welfarist discounting and feasible treaty-making, leave open the possibility that an Internationally Paretian “optimal climate treaty” will be neither ethically nor even economically optimal.

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Arrow, K.J., et al., 1996. Intertemporal Equity, Discounting, and Economic Efficiency. In: Bruce et al. 1996: 125-144.

Bruce, James P., Hoesung Lee, and Erik F. Haites (eds). 1996. Climate Change 1995: Economic and Social Dimensions of Climate Change. Cambridge: Cambridge University Press.

Cline, William R. 1992. The Economics of Global Warming. Washington: Institute for International Economics.

Dasgupta, Partha, Amartya Sen, and Stephen Marglin. 1972. Guidelines for Project Evaluation. New York: United Nations.

Kelleher, J. Paul. 2015. Is There a Sacrifice-Free Solution to Climate Change. Ethics, Policy & Environment, 18(1): 68-78.

Weisbach, David and Cass Sunstein. 2009. Climate Change and Discounting the Future: A Guide for the Perplexed. Yale Law & Policy Review, 27(2): 433-457.

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J. Paul Kelleher, « Eric A. Posner and David Weisbach, Climate Change Justice »Œconomia, 6-2 | 2016, 331-336.

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J. Paul Kelleher, « Eric A. Posner and David Weisbach, Climate Change Justice »Œconomia [En ligne], 6-2 | 2016, mis en ligne le 01 juin 2016, consulté le 15 juin 2024. URL : ; DOI :

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J. Paul Kelleher

University of Wisconsin-Madison

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