¹ John Rawls. 1999. The Law of Peoples. Cambridge, MA: Harvard University Presshereafter LP)Google Scholar §4. I will cite Rawls’s works in the text or footnotes by page or section numbers following abbreviated titles, as follows: TJ: A Theory of Justice (Cambridge, MA: Harvard University Press, 1971/1999). PL: Political Liberalism, expanded edition (New York: Columbia University Press, 2005) JF: Justice as Fairness: A Restatement, ed. Erin Kelly (Cambridge, MA: Harvard University Press, 2001).

² World Economic Forum. 2018. The Global Risks Report 2018. 11–14. Accessed 13 October 2018. http://www3.weforum.org/docs/WEF_GRR18_Report.pdf.

³ For an explanation of the obstacles to taking action about climate change, see Dale Jamieson. 2014. Reason in a Dark Time: Why the Struggle Against Climate Change Failed and What It Means for Our Future, Ch. 3. Oxford: Oxford University Press.CrossRefGoogle Scholar

⁴ Thomas Schelling. 1983. “Climate Change: Implications for Welfare and Policy.” In Changing Climate: Report of the Carbon Dioxide Assessment Committee, 453–454. Washington, DC: National Academy Press; John Broome. 1992. Counting the Cost of Global Warming, 18–19. Cambridge, UK: The White Horse Press; James Lenman. 2000. “Consequentialism and cluelessness.” Philosophy & Public Affairs 29(4):342–70; Stephen Gardiner. 2011 A Perfect Moral Storm: The Ethical Tragedy of Climate Change, Chs. 7,8. Oxford: Oxford University PressCrossRefGoogle Scholar

⁵ In fact, utilitarianism or its classic version has a straightforward answer to what our intergenerational obligation is. The principle of utility requires us to give the same weight to the welfare of future generations as to our own welfare and maximize total welfare; see Henry Sidgwick, The Methods of Ethics, 7th edition (Indianapolis: Hackett, 1907, 415–416). The problem is, as Rawls pointed out, that utilitarianism makes our obligations to future people prohibitively demanding (TJ, 286–287/253). If we postulate, as many economists do, a high marginal productivity of capital and the continuation of future generations, utilitarianism requires us not to consume but to invest almost all the resources at our disposal for the benefit of future people. Even if we take the diminishing marginal utility of wealth into account, intergenerational impartiality arguably requires us to save more than 2/3 of our income for the sake of future generations; see Kenneth Arrow. 1999. “Discounting, Morality, and Gaming.” In Discounting and Intergenerational Equity, edited by P. Portney and J. Weyant, 14–16. Washington, DC: Resources for the Future.

⁶ It is not only that different economists suggest different numbers. They find no common ground on how to resolve the discrepancy, which reflects their fundamental normative disagreement. See Nicholas Stern. 2007. The Economics of Climate Change: The Stern Review, Ch. 2. Cambridge, UK: Cambridge University Press; William Nordhaus. 2008. A Question of Balance: Weighing the Options on Global Warming Policies, Ch. 9. New Haven: Yale University Press; Martin Weitzman. 2007. “A review of the Stern Review on the Economics of Climate Change.” Journal of Economic Literature 45(3):703–724; John Broome. 2012. Climate Matters: Ethics in a Warming World, Chs.6,8. New York: W.W. Norton. This lends support to Rawls’s suspicion that discounting the welfare of future generations is merely an ad hoc device to avoid the excessively high savings rate implied by utilitarianism (TJ 1971/1999, 297–298/262).

⁷ As in the case of intergenerational obligation, classical utilitarianism implies that we should give the same weight to the welfare of foreigners as to the welfare of our compatriots. This requirement to maximize global welfare is, of course, too demanding to realistic. Utilitarians often end up with a halfway house between what their theory implies and what they think is normatively acceptable or politically feasible. For example, Posner and Weisbach suggest ‘International Paretianism’, according to which each country is ethically obliged to ratify the optimal climate treaty that maximizes intergenerational global welfare if the ratification does not make them worse off than the status quo; see their Climate Change Justice (Princeton, NJ: Princeton University Press, 2010, 178–183). It is hard to find a theoretical rationale for the status quo standard. It is not surprising that International Paretianism does not stop the disagreement in the utilitarian camp; see, for example, Mathias Frisch. 2012. “Climate Change Justice.” Philosophy and Public Affairs 40(3):225–253, 249–252 and Dale Jamieson. 2013. “Climate Change, Consequentialism, and the Road Ahead,” Chicago Journal of International Law 13(2):439–468, 454–457.

⁸ Another structural problem is that cost–benefit analysis, as it is currently practiced, hinders ethical analysis by mixing up various reasons and burying them under a few deceptively technical variables. For a similarly critical assessment of the utilitarian approach to climate change, see Ulrich Hampicke. 2011. “Climate change economics and discounted utilitarianism.” Ecological Economics 72:45–52.

⁹ Catriona McKinnon. 2012. Climate Change and Future Justice: Precaution, Compensation, and Triage, 45–46. New York: RoutledgeShe argues, for example, for the principle of compensation for the harms of climate change in the name of corrective justice (Ch.4)CrossRefGoogle Scholar

¹⁰ McKinnon 2012, p.14.

¹¹ These estimates are taken from a Representative Concentration Pathway (RCP) of the Intergovernmental Panel on Climate Change report. See IPCC, Climate Change 2014: Synthesis Report, https://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_FINAL_full_wcover.pdf, 57–64 (last accessed on 14 July 2018). They are model-based projections of global mean surface warming and sea level rise in 2081–2100, on the assumption that the total radiative forcing (RF) reaches 8.5 W/m² in 2100 on a rising trajectory (RCP8.5).

¹² For real-life examples of resource capture, see Homer-Dixon, Thomas. 1999. Environment, Scarcity, and Violence, 74–77. Princeton, NJ: Princeton University Press.My Indisia scenario is indebted to his model of how environmental scarcity and its social effects (e.g. migration, social segmentation, and weakening of the state) lead to violent conflicts.

¹³ I believe that the fair value of political liberties is a weak link where the stability of Rawls’s liberal society can be put to the test. This vulnerability might be the reason why political liberties are singled out for special treatment in a fully adequate scheme of equal basic liberties: the first principle of justice includes a proviso that the equal political liberties, and only these liberties, are to be guaranteed their fair value (PL 2005, VIII.§7; JF, §45–46).

¹⁴ Homer-Dixon, Environment, Scarcity, and Violence, 96–103. Jon Barnett and Neil Adger also emphasize that the state’s capacity to adapt to climate change is itself at risk from climate change; see their “Climate Change, Human Security, and Violent Conflict,” Political Geography 26 (2007): 639–655, 646–651.

¹⁵ See, for example, McLeman, Robert and Barry Smit. 2006. “Migration as an adaptation to climate change.” Climate Change 76:31–53; Reuveny, Rafael. 2007. “Climate Change-Induced Migration and Violent Conflict.” Political Geography 26:656–673. I offer an explanation why masses of immigrants, especially from nonliberal societies, cause disruption to the host country’s political culture and pose a threat to its stability for the right reasons in Kim, Hyunseop “A Stability Interpretation of Rawls’s The Law of Peoples,” Political Theory 43.4 (2015): 473–499, 488.

¹⁶ The liberal democratic institutions required for internal stability for the right reasons, which Indisia no longer has, are also what Rawls thinks make a society less likely to engage in international war. Rawls admits that unless each of the constitutional democratic societies satisfies these institutional requirements, the peace among them is not secure (LP, §5.3–5.4, especially 49–50).

¹⁷ In my ‘A Stability Interpretation of Rawls’s The Law of Peoples’, I explain Rawls’s idea of democratic peace and its stability in the Society of Peoples, which I call the ‘explanatory nationalism with respect to the causes of international war/peace’, in more detail (481–482).

¹⁸ Historical climatology adds plausibility to this dismal scenario by providing actual cases in which climatic instability combines with maladaptive policies to bring about social disintegration and political crisis. For example, Geoffrey Parker demonstrates that global cooling and extreme weather events in the 17th century (the Little Ice Age) resulted in crop failures and food shortages that led to forced migrations, wars, and rebellions around Europe and Asia (the General Crisis); Parker, Global Crisis: War, Climate Change & Catastrophe in the Seventeenth Century (New Haven: Yale University Press, 2013). It is worth noting that climate-induced political instabilities were mediated by the spread among the public of grievances and radical ideas that undermined the perceived legitimacy of and allegiance to the government (Part IV, 507–585).

¹⁹ IPCC, Climate Change 2014: Synthesis Report, 77–78.

²⁰ Millar, Richard, Jan Fuglestvedt, Pierre Friedlingstein, Joeri Rogelj, Michael Grubb, Damon Matthews, Ragnhild Skeie, Piers Forster, David Frame, and Myles Allen 2017. “Emission Budgets and Pathways Consistent with Limiting Warming to 1.5oC.” Nature Geoscience 10:741–747; Glen Peters. 2018. “Beyond Carbon Budgets.” Nature Geoscience 11:378–390Google Scholar

²¹ For example, we still cannot exclude the possibility that the Atlantic Meridional Overturning Circulation might collapse in the future. For AMOC and other potentially abrupt changes, see IPCC, Climate Change 2013: The Physical Science Basis, 1114–1119.

²² IPCC, Climate Change 2014: Synthesis Report, 24 (the aggregate economic costs of mitigation for stabilization at 430–480 ppm CO₂-eq, a mitigation scenario that is likely to limit warming to below 2°C through the 21st century, is estimated to be a reduction of global gross domestic product (GDP) by about 4.8% in 2100, relative to consumption in baseline scenarios that grows 3–9 times over the century = a reduction in annual GDP growth rate by about 0.14%). Stern, The Economics of Climate Change, ch.10 (the expected annual cost for stabilization at around 500–550 ppm CO₂-eq is 1±3% of GDP by 2050).

²³ For example, Nicholas Stern says, ‘An annual cost rising to 1% of GDP by 2050 poses little threat to standards of living, given that economic output in the OECD countries is likely to rise in real terms by over 200% by then, and in developing regions as a whole by 400% or more’ (The Economics of Climate Change, 267). Even those who are opposed to immediate, drastic mitigation agree that it is affordable. See, for example, Lomborg, Bjørn 2001. The Skeptical Environmentalist: Measuring the Real State of the World, 323. Cambridge, UK: Cambridge University Press.

²⁴ Without the requirement of a certain threshold of likelihood, the precautionary principle can end up being paralyzing. See Sunstein, Cass. 2007. Worst-case Scenarios, 123–133. Cambridge, MA: Harvard University Press.

²⁵ Shue, Henry, “Deadly delays, saving opportunities: creating a more dangerous world?,” reprinted in his Climate Justice, 263–286, at 264–269. Oxford: Oxford University Press, 2014 and Hartzell-Nichols, Lauren. 2017. A Climate of Risk: Precautionary Principles, Catastrophes and Climate Change, 50–51. New York: Routledge. Stephen Gardiner also appears to think that when these conditions are met, the threat is realistic/credible and the threshold that warrants precautionary measures is exceeded. Stephen Gardiner 2006. “A Core Precautionary Principle.” The Journal of Political Philosophy 14(1):33–60, footnote 62Google Scholar

²⁶ IPCC, Climate Change 2014: Synthesis Report, 40–53.

²⁷ Gleick, Peter. 2014. “Water, drought, climate change, and conflict in Syria.” Weather, Climate and Society 6:331–340; Kelley, Colin, Shahrzad Mohtadi, Mark Cane, Richard Seager, and Yochanan Kushnir 2015. “Climate change in the fertile crescent and implications of the recent Syrian drought.” Proceedings of the National Academy of Sciences 112:3241–3246; von Uexkull, Nina, Mihai Croicu, Hanne Fjelde, and Halvard Buhaug 2016. “Civil conflict sensitivity to growing-season drought.” Proceedings of the National Academy of Sciences 113:12391–12396Google Scholar

²⁸ Selby Jan, Omar Dahi, Christiane Fröhlich, and Mike Hulme 2017. “Climate change and the Syrian civil war revisited.” Political Geography 60:232–244Google Scholar

²⁹ IPCC, Climate Change 2013: The Physical Science Basis, 470–473 (Box 6.1) and 544–545. Accessed 14 July 2018. http://www.climatechange2013.org/images/report/WG1AR5_ALL_FINAL.pdf. See also Archer, David, Michael Eby, Victor Brovkin, Andy Ridgwell, Long Cao, Uwe Mikolajewicz, Ken Caldeira, Katsumi Matsumoto, Guy Munhoven, Alvaro Montenegro, and Kathy Tokos 2009. “Atmospheric Lifetime of Fossil Fuel Carbon Dioxide.” Annual Review of Earth and Planetary Sciences 37:117–134; Joos, Fortunat, R. Roth, J. Fuglestvedt, G. Peters, I. Enting, W. von Bloh, V. Brovkin, E. Burke, M. Eby, N. Edwards, T. Friedrich, T. Frolicher, P. Halloran, P. Holden, C. Jones, T. Kleinen, F. Mackenzie, K. Matsumoto, M. Meinshausen, G. Plattner, A. Reisinger, J. Segschneider, G. Shaffer, M. Steinacher, K. Strassmann, K. Tanaka, A. Timmermann, and A. Weaver 2013. “Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis.” Atmospheric Chemistry and Physics 13(5):2793–2825Google Scholar

³⁰ For example, the sea level rise due to ocean thermal expansion has much longer time scales – several centuries and even millennia – than the surface warming, because of the time required to transport heat into the deep ocean. See IPCC, Climate Change 2013: The Physical Science Basis, 100 and §13.5.4.

³¹ Gardiner, Stephen. 2011. “Rawls and Climate Change: Does Rawlsian Political Philosophy Pass the Global Test?,” Critical Review of International Social and Political Philosophy 14(2):125–151, 143–144CrossRefGoogle Scholar

³² John Broome argues that the duty not to harm requires each of us not to emit GHGs without compensating the people who are harmed or offsetting our emissions; see his Climate Matters, Chs. 4 and 5. Martin Traxler argues that no one is morally required to make cuts to their subsistence emissions, even if the subsistence emissions inflict harm on others. As self-defense may excuse the commission of an injury and even a murder, so does the necessity for subsistence make our indispensable emissions and the resulting infliction of harm they cause excusable. See his “Fair chore division for climate change,” Social Theory and Practice 28 (2002):101–134, 107–108. For the distinction between subsistence emissions and luxury emissions, see Shue, Henry. 1993. “Subsistence emissions and luxury emissions.” Law and Policy 15:39–59CrossRefGoogle Scholar

³³ It is not expected that most citizens in a well-ordered society are in such command or control of themselves as to fulfill the requirements of right and justice with complete ease and grace (TJ 1971/1999, 478–479/419). A conception of justice is not stable if support for its principles and basic institutions can be (re)generated only with the help of such extraordinary self-command or heroic self-control.

³⁴ Rawls assumes that a society exists ‘in perpetuity: it produces and reproduces itself and its institutions and culture over generations and there is no time at which it is expected to wind up its affairs’ (PL 2005, 18).

³⁵ A liberal society’s just basic structure can be threatened by international factors such as war, military interventions, or an uncontrollable, large-scale influx of immigrants/refugees. In my ‘A Stability Interpretation of Rawls’s The Law of Peoples’, I have argued that protecting liberal societies from international threats and making them more stable is an underlying but central role of Rawls’s principles of international justice. If my stability interpretation is correct, this new principle of international, intergenerational justice plays basically the same role as Rawls’s own principles of international justice.

³⁶ In this paragraph, I am indebted to Ronzoni, Miriam. 2009. “The Global Order: A Case of Background Injustice? A Practice-Dependent Account.” Philosophy and Public Affairs 37(3):229–256.

³⁷ Another method of preventing anthropogenic GHG emissions from contributing to climate change is to reduce the amount of absorbed solar energy in the climate system (Solar Radiation Management by, for example, stratospheric aerosol injection and cloud brightening). Much more work seems to be required to understand the costs, benefits, and in particular risks of catastrophes that threaten stability before we (if ever) find a safe, reliable method of SRM or other ‘geoengineering’. IPCC, Climate Change 2013: The Physical Science Basis, 627–635.

³⁸ This amount of CO₂ that can be emitted into the atmosphere for a given temperature target is sometimes called the ‘carbon budget’. See IPCC, Climate Change 2013: The Physical Science Basis, 1112–1113; Frame, David, Adrian Macey, and Myles Allen. 2014. “Cumulative emissions and climate policy.” Nature Geoscience 7 692–693; Rogelj, Joeri, Michiel Schaeffer, Pierre Friedlingstein, Nathan Gillett, Detlef van Vuuren, Keywan Riahi, Myles Allen and Reto Knutti 2016. “Differences between Carbon Budget Estimates Unravelled.” Nature Climate Change 6:245–252.Thanks to an anonymous reviewer of International Theory for pointing this out to meGoogle Scholar

³⁹ IPCC. 2014. Climate Change 2014: Synthesis Report. In Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, edited by R. K. Pachauri and L. A. Meyer, 151. Geneva, Switzerland: IPCC.

⁴⁰ Caney, Simon. 2012. “Just Emissions.” Philosophy and Public Affairs 40(4):255–300, 293–295CrossRefGoogle Scholar