Climate Change and the Threat of Disaster: The Moral Case for Taking Out Insurance at Our Grandchildren's Expense

Is drastic action against global warming essential to avoid impoverishing our descendants? Or does it mean robbing the poor to give to the rich? We do not yet know. Yet most of us can agree on the importance of minimising expected deprivation. Because of the vast number of future generations, if there is any significant risk of catastrophe, this implies drastic and expensive carbon abatement unless we discount the future. I argue that we should not discount. Instead, the rich countries should stump up the funds to support abatement both for themselves and the poor states of the world. Yet to ask the present generation to assume all the costs of drastic mitigation.is unfair. Worse still, it is politically unrealistic. We can square the circle by shifting part of the burden to our descendants. Even if we divert investment from other parts of the economy or increase public debt, future people should be richer, so long as we avert catastrophe. If so, it is fair for them to assume much of the cost of abatement. What we must not do is to expose them to the threat of disaster by not doing enough.

Whether we should 'discount' consumption benefits to future people -in large part because they will be richer -lay at the centre of the debate over the 2006 Stern Review on the Economics of Climate Change. Critics argued that on Stern's projections, even with substantial climate change, future people would still be many times wealthier in 2200 than they are today (Godard, 2008, p. 33). The Review, Partha Dasgupta (2007, p. 6) charged, had assumed 'that the distribution of well-being among people doesn't matter much, that we should spend huge amounts for later generations even if, adjusting for risk, they were expected to be much better off than us'. The present article argues that Stern was right not to discount the consumption of future people. The problem with most economic analyses lies deeper -namely, in the assumption that we should maximise utility in the first place.
In the last 40 years, utility maximisation, still largely taken for granted by economists analysing climate change, has come under sustained philosophical attack. The most influential political theory of the second half of the twentieth century, John Rawls' A Theory of Justice (1999), explicitly rejects utilitarianism in favour of giving priority to the worst off. Others stress the importance of ensuring that people have enough to lead sufficient livesafter which point further increases in consumption or utility matter less, or not at all (Frankfurt, 1987;Huseby, 2010). Both views have played a role in the climate change debate, and both can explain why we must not sacrifice today's poor to tomorrow's rich.
Extended to the intergenerational context, the priority and sufficiency views require us to minimise deprivation -now and in the future. If we knew for sure that future generations of human beings would be materially richer, then that would weaken the case for slashing GHG emissions. But disaster cannot be ruled out. Faced with catastrophic threats, we should minimise expected deprivation. Since runaway global warming could affect so many for so long, prioritarianism and sufficientarianism both imply drastic abatement. By any moral measure, the North should pay for it. But if it refuses, action is needed even if it comes at the expense of the South.
In reality, neither the North nor the South appears ready to step up to the plate.We must tap resources from somewhere -and better from rich people than from poor ones. This article argues that we should look to the rich of the future. If we can shift part of the burden of GHG abatement to our descendants, it is entirely fair to do so. Provided we avert catastrophe, this should still leave future people richer than their counterparts today. They will be able to pay off debt, replace infrastructure or do without some natural resources without giving up too much.What would be truly wrong would be to risk disaster by not doing enough.

The Long Shadow of the Future
Much of the effect of our GHG emissions is likely to endure for hundreds or thousands of years. This makes the weight we accord to future people extraordinarily important (Grubb, 1995, p. 472). Utilitarianism normally weights everyone's well-being equally, exposing it to the objection that it can demand huge sacrifices. Any permanent loss, however small, becomes with time all but infinitely costly. In the case of global warming, GHG abatement 'would confer benefits not only in 2100 but in every subsequent year, perhaps for millions of years' (Posner, 2004, p. 152).We might be required to make huge sacrifices for the sake of trivial future benefits, because over time those benefits would add up to be so great (Nordhaus, 2008, pp. 182-3).
We can undertake a good deal of abatement at minimal cost. Some measures may even save us money (Spash, 2005, pp. 162-3). Still, critics argue that climate mitigation on the scale envisioned by Al Gore or the Stern Review will not come cheap.While William Nordhaus estimates that even these plans are likely to cost less than 2 per cent of world income (2008, p. 90;compare Helm, 2008;Quiggin, 2008, p. 195), in absolute terms this is a large sum. At the same time, economists widely expect per capita consumption to go on rising (Dietz et al., 2008, p. 378). This raises an objection to deep emissions cuts on grounds of equity: 'Can we justify current generations sacrificing 2-3% of GWP to increase the wealth of future generations who even after deduction for the high damage scenario are 2-15 times richer than the present generation?' (Lind, 1995, p. 384).
It is bad enough that refusing to discount could require today's rich to sacrifice for those who will be richer tomorrow.What is really troubling is that drastic abatement could impose a heavy burden on the world's poor. '[T]he one thing that is certain about the global warming issue is that an immediate significant cut in fossil fuel consumption means a drastic cut in world energy consumption and hence in standards of living', warns Wilfred Beckerman (1995, p. 79). 'And the social and political upheavals to which this would lead would also be catastrophic. Furthermore ... a rise in income levels is the only way that the urgent environmental problems facing the 75 per cent of the world's population that live in developing countries can be overcome.'While rich countries may be able to weather a depression without widespread death and disease, this is not true of the poor ones (Beckerman, 1995, p. 16;Malnes, 1995, p. 125).
The solution, in the eyes of many economists, is to discount benefits to future people. This will prevent the present from being sacrificed to an immensely populous future (Arrow, 1999, pp. 14-5). Moreover, discounting seems consistent with the standard assumption that an additional unit of income to the rich provides less utility than the same increment to the poor. As Colin Price (2003) notes, diminishing marginal utility is widely seen as the 'respectable case for discounting'.
Nevertheless, this solution is ad hoc: discounting the future does nothing to solve the general problem that utilitarianism is too demanding (Caney, 2008, pp. 549-50). Moreover, it misleadingly implies that future people's consumption counts for less, when what we really mean is that the consumption of the rich matters less, or that we value equality among generations, or that no generation should be asked to give up too much. Worse yet, utilitarianism still requires that the poor be sacrificed to the rich if the latter can gain enough. Seeking to avoid this, we might put another finger on the scales, so that benefits that convey the same amount of utility matter more when they go to the badly off (Cowen and Parfit, 1992, pp. 148-9). Nevertheless, if there are enough well-off people, or if the benefits extend far enough into the future, the needs of the poor can still be outweighed by the luxuries of the rich (Crisp, 2003, p. 754;Meyer and Roser, 2009, pp. 234-5;Roser, 2009b, p. 15).
The root of the problem is the belief that we should maximise utility in the first place. In fact, the duty seems much clearer to ensure a 'minimum level of well-being below which no generation should fall' (Broome, 1992, p. 106;Roser, 2009b, pp. 13-5). This is usually presented as protecting people's rights (Caney, 2008;Spash, 2005). Even those who reject strong positive obligations to the inhabitants of other countries can agree that it is wrong, other things being equal, to harm them (Shapcott, 2008). The same goes for other generations (Davidson, 2008). Thomas Schelling's comparison of climate change mitigation with foreign aid misses the mark because the question is not one of helping future people (Sunstein, 2007, pp. 266-7). A closer analogy would be with not raping and pillaging one's neighbours.
Still, we should not focus on the negative right not to be harmed by climate change to the exclusion of the positive right to development. Some draw a sharp distinction between acts of commission and acts of omission, seeing only the former as rights violations. Anthropogenic climate change is an act of commission, whereas many see failing to address poverty as an act of omission (Dasgupta, 2008, p. 159;Spash, 2005, pp. 230-1). Indeed, if our duty to our fellow creatures is simply to avoid harming them, or to leave them 'enough and as good' of the earth's natural endowment as we have enjoyed ourselves, then we can easily justify draconian environmental protection (Elliot, 1986;compare Davidson, 2008). Yet many will find this implausibly libertarian. If the same resources can spare ten people from the effects of climate change or save a thousand from naturally occurring malaria, are we really obliged to choose the former on the grounds that anthropogenic carbon emissions violate people's negative rights, whereas anopheles mosquitos do not? Surely it is unfair that anyone should suffer undeservedly, whether as the result of human-induced harm or natural circumstances (Arneson, 2000, p. 346).

Priority to the Deprived
If we reject a sharp distinction between negative and positive rights, perhaps it is best to aim at minimising deprivation (Wolf, 2009, p. 356). Both the priority and sufficiency views stress this goal, but they define it differently. Prioritarians in turn differ among themselves in how much preference they accord to the worst off. The worse off a person is, the greater value weighted prioritarianism accords to benefiting him or her. Nevertheless, benefits to the well off can outweigh this preference if they are big enough. In contrast, Rawls (1999) rejects utilitarianism in favour of absolute priority for the worst off (Crisp, 2003, pp. 752-4). Under conditions of moderate scarcity, if everyone followed this rule, it would guarantee enough to live on. In the real world, however, where some face extreme scarcity and not everybody does as Rawls says they should, absolute priority could mean unacceptable trade-offs (McKerlie, 1994;Wolf, 2009, p. 357). If climate change threatens to kill a hundred people, absolute prioritarianism may require us to prevent this even if the same resources spent differently could rescue a million people from desperate poverty. 2 Sufficientarians seek to ensure that people can lead a satisfactory life. They set the bar higher than survival: a sufficient life entails more than 'merely having enough to get along or enough to make life marginally tolerable', and is 'deeply satisfying' (Frankfurt, 1987, p. 38;1997, p. 5). Whereas absolute prioritarianism says we must give priority to the worst off regardless of the cost, sufficientarianism may allow us to help another group of badly off people, if we can do more for them, or if they are greater in number (Meyer and Roser, 2009, p. 224;Wolf, 2009, p. 352). Yet our goal cannot be simply to maximise the proportion of people with good lives. That would do too little for those in desperation. It would tell us to help two poor people rather than one person who is starving. 3 The most plausible solution combines the sufficiency and priority views. It gives absolute priority to ensuring that people have what they need for a good life, and weighted priority to reducing more severe deprivation (Brown, 2005;Crisp, 2003). We thus give priority to reducing average deprivation, measured in terms of both its extent and its severity. 4 If future people are our moral equals, there seems no reason not to minimise deprivation between generations as well as within them. This means putting the needs of the hungry present before the wealthy future (Gaspart and Gosseries, 2007). It also means putting poor countries before rich ones. The latter should bear most of the burden of mitigating climate change. Compared with the North, even decades later much of the South is likely to be poor. Spending by rich states today will still help people -now or in the future -who are on average worse off (Schelling, 1995, pp. 398-9). Even so, some say the North would get more bang for its buck by spending the money on other things. Rich states could pay compensation to poor ones for climate change, offer direct assistance in adaptation or simply invest the money in other worthy projects, such as wiping out malaria. 5 In short, it may seem that equity speaks not for putting the brakes on climate change, but for helping the poor ride it out.

The Threat of Disaster
This is not the case.While investing elsewhere may enable us to protect or compensate future generations, there is no guarantee that we will actually do it.We or our children might blow the money on a spending spree instead. Even if environmental preservation has a lower aggregate pay-off, it may be a surer means of seeing that the benefits reach the right parties (Farber and Hemmersbaugh, 1993, pp. 297-8;Lind, 1995;Tremmel, 2009, p. 73). Moreover, though poor humans may adapt to climate change, many non-humans clearly will not (Shue, 1995, p. 255).Worldwide, there are 50 birds for every human. Even in densely settled Britain, wild mammals considerably outnumber human beings (Gleich et al., 2002, pp. 262-7). The destruction of these animals' habitats can only produce enormous suffering. If animals have moral standing, then intergenerational justice must take account of their interests (Krebs, 2001). Finally, climate change could turn out worse than we expect, and leave our descendants poorer than we are.
Many argue that we should discount the future because future people will be richer. The sensible ones recognise that this is a gamble, even if it is a gamble with good odds (Sunstein, 2007, p. 258). Even an optimist like Beckerman admits the 'remote possibility' that global warming could impoverish future generations (Beckerman and Hepburn, 2007, pp. 190-1;Beckerman and Pasek, 2001, pp. 99-105). If we are very unlucky, it could 'effectively destroy planet Earth as we know it' (Weitzman, 2009, p. 5) or even leave the earth uninhabitable (Broome, 1992, pp. 15-6, p. 23). Weitzman (2009, p. 1) notes 'deep structural uncertainty in the science coupled with an economic inability to evaluate meaningfully the catastrophic losses from disastrous temperature changes. The climate science seems to be saying that the probability of a disastrous collapse of planetary welfare is nonnegligible, even if this tiny probability is not objectively knowable'.
One of the most prominent advocates of a go-slow approach to climate mitigation, William Nordhaus (2008, p. 28, pp. 145-7), rules out such 'genuinely catastrophic outcomes' by assumption, noting that 'preliminary runs' of his model 'suggest' that we do not need to worry about 'a permanent Great Depression, civilizational collapse, or even human extinction'. Yet he confesses that '[u]ntil geophysical modelers develop mechanisms for generating abrupt or catastrophic changes, there is little that economic models ... can do to introduce results based on established scientific findings in integrated assessment models'. Indeed, '[w]e cannot rule out the potential for catastrophic impacts that might justify trillions of dollars of abatement costs'. Nordhaus thinks climate change will not wreck the planet, but he isn't sure. Meanwhile,'[w]e should start with the clear and present dangers, after which we can turn to the unclear and distant threats'.
This logic is weak. There is no reason to be confident that 'starting with the clear and present dangers' will work. If climate change poses the threat of catastrophe, we may need to act now (compare Hansson, 2004, p. 357). Moreover, the fact that a threat is unclear says nothing about whether it is small.We are dealing not with a well-defined risk, but with an uncertain chance of disaster. We might gamble and have bad luck; we could also be wrong from the outset about what the odds really are (Arrow et al., 1996, p. 67;Ryan, 2007, p. 176). We are especially likely to misjudge the probability of unlikely risks (Bier et al., 2004, p. 78, p. 93). Uncertainty about climate change gives grounds for greater caution rather than less (Broome, 1992, pp. 17-8;Stern, 2009, p. 35). As Weitzman (2009, p. 5) observes: The tiny probabilities of nightmare impacts of climate change are all such crude ballpark estimates (and they would occur so far in the future) that there is a tendency in the literature to dismiss altogether these highly uncertain forecasts on the 'scientific' grounds that they are much too speculative to be taken seriously ... [But] other things being equal, the more speculative and fuzzy are the tiny tail probabilities of extreme events, the less ignorable and the more serious is the impact on present discounted expected utility for a risk-averse agent.
Here the preponderant weight of the future comes back into play. Both egalitarianism and utilitarianism admit a case for discounting losses to future people if they will be better off. But neither an aversion to inequality nor declining marginal utility justifies discounting their interest in being as well off as we are. Global warming could impoverish future people for many decades, for centuries or even for good. Even if it did not leave them economically worse off, it could deprive them of good health or other basic needs, bringing them below the threshold of sufficiency in another fashion. Rich people as well as poor ones deserve protection against being cooked (Caney, 2008, pp. 550-1;Davidson, 2008, p. 472;Spash, 2005, pp. 228-9). In contrast, provided economic growth continues, the material misery of today's poor countries 'must eventually be eradicated' (Beckerman and Pasek, 2001, p. 119).
If economic growth does not continue, this is likely to be the result of runaway climate change or another catastrophe like nuclear war. 6 In the United States, 'increases in prosperity are likely notwithstanding the aging of the Baby Boom generation', observes Neil Buchanan (2009c, pp. 1270-2, emphasis added), with even pessimistic forecasts showing impressively high cumulative economic growth leading to very high average future living standards ... The estimates from the Social Security Trustees ... have been very steady over the years, and the scale of revisions necessary to result in a forecast of zero net growth (or something even close to that level) over a several-decade span appears to be beyond reason. Short of unpredictable cataclysms (weather-related disasters, world war, the collapse of global capitalism), these forecasts are apparently among the most solid available.
If we must choose between two policies, both of which may impoverish people's lives, we ought to choose the one that minimises expected per capita deprivation. This is a product of the share of the total population -present and future -who are at risk, the estimated probability of their falling below the threshold of sufficiency and the likely severity of the deprivation. 7 Given the vast number of future people, barring the chance of human extinction, any significant likelihood of permanent impoverishment must outweigh even a high probability of continued poverty in parts of the world over the next few generations. 8 Strictly speaking, such trade-offs are unnecessary; ambitious abatement measures need impoverish no-one. While their cost would be large in absolute terms, as a percentage of world income they are small, with Nordhaus (2008, p. 90) estimating their cost at 1.5 per cent. Weitzman (2007, p. 720) notes the Stern Review's stress on the immorality of relegating future generations to live under the shadow of the open-ended possibilities of uncertain large-scale changes in the climate system, when for a mere annuity cost of a per cent or two (or at most three) of GDP each year we might have purchased an insurance policy on their behalf that avoided this scary uncertainty (or at least greatly reduced it).
Ambitious mitigation need not bring a single person below the poverty line if we were only prepared to redistribute enough resources. 9 'The fallacy', Richard Posner (2004, p. 115) observes,'is to think that we have a choice between only two policies: we can either expand health insurance or take measures against catastrophic risks.We can do both.We would just have to give up something else'.

Motivating Mitigation
But it does not seem we will. Since today's rich states reap most of the benefits of carbon emissions, while externalising most of the costs to other countries, species and generations, they have a strong incentive to continue (compare Gardiner, 2006b). Nor do the world's poor seem ready to make cuts that restrict their economic development (Malnes, 1995, p. 125). Powerful countries might impose the costs of mitigation on weaker ones -a process that may already be under way (Isla, 2009). Of course, this would be deeply unfair. In particular, policies that deprived the poor of necessities so that the rich could continue their 'luxury emissions' would be a crying injustice (Shue, 1993). All the same, it would be a lesser injustice than risking long-term catastrophe. As Clark Wolf (2009, p. 373) puts it, 'Unless our efforts to mitigate the effects of climate change will cause more misery and deprivation than they will relieve, we have an obligation of justice to undertake them'. Even the prospect of condemning several more generations in the South to poverty -terrible in itself -dwindles next to the danger of permanent impoverishment.
Nevertheless, far better that the rich should pay for abatement. The problem is that they are unwilling to do enough. And indeed, while they should do more, it does not seem quite fair to ask them to bear the whole burden. We ought to pursue ambitious mitigation, because we live at a time when climate change is coming to a head. At the same time, our descendants are likely to be materially far richer. The problem is not that they are likely to be impoverished if we do not do enough. Rather it is that if things turn out much worse than we expect, they could be disastrous indeed. Abatement is akin to taking out an insurance policy, or investing in bonds rather than stocks: it 'reduces the variance in what may happen' (Broome, 1992, pp. 17-8;Roser, 2009a, p. 21, n. 46). 10 Suppose I hold a well-paid job with good prospects for promotion. Barring accidents, I can expect to save enough to leave my heirs a large legacy. Yet if I am killed on the job and a market crash wipes out my savings, I will leave my family penniless. Of course I should take out life insurance. That my heirs will probably be richer is no excuse for exposing them to disaster. Yet finding the payments onerous, I may be tempted to skimp, and hope for the best. That would be the wrong choice. It would be better to save less, and use the money to pay the insurance premiums. That would not be unfair to my heirs: they will still have more than I had. Nor is it unfair to put my savings in bonds with a lower rate of return. 11 If I live to a ripe old age, my heirs will inherit a smaller fortune, but still more than I have now. Since I already have enough to live comfortably, they will have comparatively little interest in 'potential gains ... above the minimum that can be guaranteed by the maximin approach'. 12 This is a paradigmatic case for precautionary action (Gardiner, 2006a, p. 47). It is better to inherit less, but to be spared the threat of disaster.
Likewise, in the case of catastrophic threats, we ought to take out 'insurance'. It is fair for the rich to make their still richer descendants pay part of the premium (compare Lind, 1995, p. 382). Indeed, if we anticipate that our descendants will be richer, there is some case for transferring resources from the future even if we use them simply for consumption (Gaspart and Gosseries, 2007;Zelenak, 2009).When we borrow from our grandchildren for their own protection, the case becomes overwhelming. Some find the notion that we could legitimately pass on costs to our descendants hard to swallow. Is not 'seeing our children and grandchildren do better than we have done ... the real promise of America', as Senator Hatch asserts (2009)? It is hard to see why this must be the case.We have no reason to think that they will be more virtuous or harder working than we are. As Brian Barry (1983, p. 20) observes, 'none of the usual justifications for an unequal claim -special relationships arising in virtue of past services, promises, etc. -applies here' (compare Tremmel, 2009, p. 175). An inheritance equal to our own is the obvious baseline. Deep cuts in GHG emissions promise our descendants the best chance of receiving at least that much.
The challenge is to find ways of transferring resources from the future (Lind, 1995, pp. 382-3). One possible means is public debt (Bradford, 1999, p. 42;Revesz, 1999Revesz, , p. 1007. Economists have long debated whether the present generation is able to pass on the burden of the public debt at all. 13 Indeed, it does not seem possible for the present generation taken as a whole to borrow money from the future. Any loan made now comes out of today's spending and investment, and will in turn be repaid to future people (Buchanan, 2004, pp. 324-5). Nevertheless, public debt may transfer wealth from present-day creditors to presentday citizens and taxpayers, and in turn from future taxpayers to future creditors (Lerner, 1961). It benefits today's taxpayers at the expense of tomorrow's. And it is today's taxpayers who must be persuaded to foot the bill of carbon mitigation.
Some deplore intergenerational cost shifting as unjust (Boettcher and Tremmel, 2005;Wolf, 2008). 'What will ... $400 million for climate change research do to help you and your family?' demands US Representative Michele Bachmann (2009), complaining that the Obama administration's stimulus package will 'cost the American taxpayers, their children and their grandchildren more than $1 trillion'.Warning of 'global warming taxes that will hike costs for every American who turns on a light switch', Representative Lynn Westmoreland (2009) denounces a 'felonious theft from future generations with the trillions in IOUs we'll be handing them'. Yet even if running up debt means our descendants pay higher taxes, or receive fewer government benefits, this will not make them poorer than we are so long as the rise in pre-tax incomes keeps pace (Buchanan, 2004, p. 314;, p. 1292Gaspart and Gosseries, 2007, pp. 206-7). Critics of deficit spending must explain why we owe them more. 14 At some point government borrowing could become unsustainable (Shaviro, 2009). If Britain, for example, cannot issue further debt without risking a 'buyers' strike' from the bond market (Lanchester, 2010;compare Weale, 2009, p. 5), then further deficit financing may not be an option. The question is whether most leading industrialised economies are near that point. It is hard to believe that after so much deficit spending -including the huge sums spent lately on the bank bail-outs -debt-funded climate change mitigation is the feather that would break the camel's back. Indeed, some argue that with national economies functioning at less than full capacity, deficit spending is likely to stimulate the economy and private investment, increasing resources both for present and for future people. In any case, the question is a practical one, rather than a matter of intergenerational justice. If we have reason to worry about deficits at all, it concerns their fiscal sustainability today, not because they amount to 'generational theft' from our descendants (Buchanan, 2009b, pp. 50-2).
Another way to compensate ourselves at the future's expense is to save and invest less in other areas, spend less on research and development and consume resources in an unsustainable fashion (compare Modigliani, 1961, p. 736;Revesz, 1999Revesz, , p. 1007Zelenak, 2009Zelenak, , p. 1361. ' [A] global climate initiative that is for reasons economic or political likely to crowd out basic scientific research', Lawrence Summers and Richard Zeckhauser argue (2008, p. 133),'should be judged more harshly than an equivalent project that would affect only consumption'. Should it? Only if we ought to increase the wealth of the future. If future people are likely to be richer, there is at least as strong an argument for investing less (Mishan, 1963, p. 539, n. 16). ' [N]o substantive case', maintains Clive Spash (2005, p. 238), 'has been made that controlling emissions would do more than reduce the rate of growth of material consumption for industrially developed economies'. Growth in living standards comes not only from saving and sacrifice, but also from technological and institutional innovation (Brennan, 2007, p. 280;Gaspart and Gosseries, 2007, p. 206;Tremmel, 2009, pp. 165-6). If we fund climate change mitigation by dis-saving in other areas, this can and will be offset up to a point by the accumulation of human knowledge. 15 There is also a strong pragmatic argument in favour of burden shifting to the future: the present generation seems more likely to support abatement if it can pass on part of the costs (Bradford, 1999, p. 42;compare Weale, 2009, p. 6).While voters might baulk at policies that explicitly transfer wealth from the future (Zelenak, 2009(Zelenak, , p. 1381, they already elect politicians who run up debt merely to fund increased consumption (Kielmansegg, 2003).When debt is used to reduce the threat to future generations, as in the case of a just war, the moral case for burden shifting is far stronger.'Quite aside from obvious incentive considerations', as Franco Modigliani (1961, p. 753) observes, 'there may be perfectly good equity reasons for lightening the burden of the generation that suffered through the war by granting them a more comfortable life after the war, at the expense of later generations'. The same goes for lightening the sacrifices our generation must bear to avert the threat of catastrophic climate change. Faced with curbs on carbon emissions, Eric Posner (2007, pp. 142-3) warns, American '[c]onsumers would respond by saving less and spending more at the margin' and 'might simply demand additional government programs that transfer wealth from the future to the present -for example, tax cuts without spending cuts and thus increased debt, or energy projects that degrade the environment in a manner outside the jurisdiction of the [US Environmental Protection Agency], or disinvestment in basic research'. That would be an acceptable price to pay. Our duty is not to make the rich of the future richer, but rather to avert disaster.
Transfers of wealth from the future should be used to fund abatement not only at home in the North, but also, and especially, in the South. Not only is these countries' participation essential in the long run, but here there is the strongest case on the basis of equity for tapping the wealth of the North's descendants, who can be expected, if catastrophe is averted, to be far richer than most inhabitants of the South today (Buchanan, 2009a(Buchanan, , pp. 1404, p. 1256. It is well known that the rich countries contribute less foreign aid than philosophers say they should. They may be more willing to fork out if they can pass on part of the bill. Happily, there is nothing unjust in their doing so. 16

Conclusion
Utilitarianism notoriously allows the trivial interests of the many to overwhelm the vital interests of the few. This is enough, in Nordhaus' (2008, pp. 182-3) eyes, to damn the Stern Review. 'Using its growth projections', he charges, the Stern Review would justify reducing per capita consumption for one year today from $6,600 to $2,900 in order to prevent a reduction of consumption from $87,000 to $86,900 starting two centuries hence and continuing at that rate forever after. This bizarre result arises because the value of the future consumption stream is so high with near-zero time discounting that we should sacrifice a large fraction of today's income in order to increase a far-future income stream by a very tiny fraction.
Nordhaus' solution is to discount the value of additional consumption by future people. This solution is misleading. In reality, we do not -or, at any rate, should not -believe that people's consumption matters less merely because they will live in the future. As Tyler Cowen and Derek Parfit (1992, p. 148) advise, 'we should say what we mean'. What we mean is that no benefits to the well off, however numerous the latter may be, can ever justify depriving the needy.We need an ethic that will not allow the luxuries of the rich to trump the needs of the poor. We find this in minimising expected deprivation.
Once we reject utilitarianism, we no longer need to discount. We are more than rich enough to minimise expected deprivation without assuming intolerable burdens. In the case of climate change, we have the choice of two ideal-type strategies for doing this. On the one hand, we can pursue ambitious mitigation; on the other, we can let the planet warm on the assumption that our savings and additional growth will allow us to adapt successfully to climate change, or compensate for the damage (Toman, 2005, p. 82). 17 Adaptation and compensation may work out -for humans, if not for other species -but they carry the small chance of long-term or even permanent catastrophe. In contrast, so long as mitigation is not so drastic as to halt growth, within a century even today's poor states should be far richer than they are today. Given the vast number of future people who would suffer from runaway climate change, minimising expected deprivation calls for precaution. As Wolf (2009, p. 373, emphasis in original) says,'Present investment to mitigate climate change does not aim to make later generations better off than earlier ones. Instead, it aims to protect later generations from risks that might make them much worse off than earlier ones'. 18 We can easily afford to spend 1 or 2 per cent of world income and still meet everyone's basic needs. The benefits the rich would forgo in order to avert the threat of disaster are trivial in comparison. Yet they refuse to do so. Fortunately, through long-term borrowing or diverting funds from other investments, we can ensure that the rich of the future share the burden of climate mitigation. As Wilfred Beckerman and Joanna Pasek (2001, p. 105, emphasis added) observe: Future generations are likely to be much richer than is the current generation, and there is little reason to believe that the steady rise in real incomes will be significantly reduced by climate change ... However, we do have a moral obligation to take account of the possibility, however small, that climate change could seriously depress the living standards of future generations. 19 Well said. But this means that the world has little to lose and much to gain from passing on part of the burden of abatement. Our much richer descendants can well afford to pay off some debt if this ensures that they really are richer.