Climate Change and the Future: Discounting for Time, Wealth, and Risk


There is no quality in human nature, which causes more fatal errors in our conduct, than that which leads us to prefer whatever is present to the distant and remote, and makes us desire objects more according to their situation than their intrinsic value.1

It is widely recognized that the Earth's climate is undergoing profound changes. The most authoritative analysis is that produced by the Intergovernmental Panel on Climate Change (IPCC). In its most recent report, the Fourth Assessment Report, the IPCC confirmed that the Earth's climate is getting warmer and is projected to continue to do so. The report employs six different scenarios. According to these six scenarios, the likely increase in temperature ranges from 1.1°C to 6.4°C and the likely increase in sea level ranges from 0.18 meters to 0.59 meters.2 Climate change will have very severe impacts on many people—producing poverty, disease, instability, and death from freak weather events. It will, in particular, have dire consequences for members of developing countries. I have argued elsewhere that it jeopardizes fundamental human rights.3 In light of this, there is a strong case for engaging in a vigorous policy of mitigation.

Some, however, query this, arguing that many of the impacts of climate change will be felt in the future and that future disadvantages can be discounted. My purpose in this paper is to explore the issues of intergenerational equity raised by climate change. To do so, it is necessary to start with a recognition of the intergenerational nature of anthropogenic climate change. Greenhouse gases have a long life span and emissions at one time can exert a considerable influence on events decades, even millennia, later. To take the example of carbon dioxide: molecules of carbon dioxide can last for very different time periods, depending on whether they are located in the atmosphere or near the surface of the ocean or deep in the ocean. The average lifetime is approximately one hundred years.4 The emission of greenhouse gases thus raises questions of intergenerational, as well as international, equity. What obligations do we owe to future generations? May we (should we) apply a positive social discount rate and devote more resources to our contemporaries than to future generations?

The answers to these questions make a considerable difference not simply to whether current generations should engage in mitigation or not. Suppose that we think (as very many do) that some mitigation is necessary, the social discount rate also bears on the question of how much current generations should mitigate and this remains hotly contested. To ask by how much current generations should lower emissions requires one to assess their interests with the legitimate interests of future people and so the question of whether a discount rate should be applied to future generations is crucial here. As many have emphasized, the resources to be spent on combating climate change (both the funds that should be spent on adaptation and the opportunities foregone by mitigating) could be spent on other contemporary problems—including malaria, AIDS, malnutrition, and global poverty.5

A number of different reasons have been suggested as to why current generations may legitimately favor devoting resources to contemporaries rather than to future generations. These—either individually or jointly—challenge the case for combating climate change. In this paper, I distinguish between three different kinds of reason for favoring contemporaries. I argue that none of these arguments is persuasive. My answer in each case appeals to the concept of human rights. It maintains that a human rights-centered perspective to climate change enables us to address each of these reasons.

I. The Social Discount Rate

To address the question of how current generations should make decisions which bear on the interests of future people, it is essential to introduce the concept of a social discount rate.6 This concept has been discussed by economists from Alfred Marshall, A. C. Pigou, and Frank Ramsey to contemporary economists like Sir Nicholas Stern.7 It refers to the rate by which the claims of future generations to resources currently held by current generations diminishes or increases or remains constant over time. A social discount rate, thus, determines the extent to which resources should be devoted to people's interests now in preference to people's interests at a later date.8 The higher the positive social discount rate the less should be spent on the future. To explicate the concept further and relate it to the issue of climate change, it is useful to have some figures in front of us. The Stern Review has famously argued that the cost of attaining a stabilization level of 550 pm CO2e, thereby mitigating climate change, amounts to approximately one percent of global GDP per annum.9 Eric Neumayer calculates that, in practice, this would require an outlay of $350 billion per annum rising to a figure of $1000 billion by 2050.10 So the question to be examined is whether this sum is better spent on current generations or on future generations.

Why might one legitimately hold that the money should be spent on current generations rather than future ones? Standard analyses of the social discount rate comprise four separate components, each of which shall be dealt with in turn.

A. First, there is what economists call pure time preference. Some hold that it is appropriate to ascribe a lower weight to human interests the further they are in the future just because of the fact that they exist in the future. Thus, one reason for adopting a social discount rate is that one thinks it appropriate to reflect pure time preference. Pigou, Ramsey and, more recently, Sir Nicholas Stern have argued that pure time preference is morally illegitimate.11 Similarly, Roy Harrod famously says that “pure time preference [is] a polite expression for rapacity and the conquest of reason by passion.”12 On his view, it is “a human infirmity.”13 Henry Sidgwick takes a similar view, stating that “the time at which a man exists cannot affect the value of his happiness from a universal point of view; and that the interests of posterity must concern a Utilitarian as much as those of his contemporaries.”14 Pure time preference, however, is far from being the only relevant consideration.

B. Second, we need to ascertain the correct principle of intergenerational equity. Suppose that one holds that there should not be any pure time preference. One might still permissibly decide to devote resources to current people over future people for a second reason, depending on what principle of intergenerational equity one adopts. One way to see this is to set intergenerational matters to one side for a moment. Consider a theory of justice that applies solely to a current generation. It will have several component parts. First, it has to decide whether all persons have equal moral status or whether some have greater moral standing than others. (In the intergenerational context, those who subscribe to pure time discounting are rejecting the principle of equal moral standing.) Now once we have determined this first issue we then have to decide what distributive principle applies. Should it be economic equality or a Rawlsian difference principle or libertarianism or a desert theory or a sufficientarian approach or something else? Now the same question applies at the intergenerational level. Once the issue of time discounting has been addressed, we then need to identify whether relations between generations should be determined by a principle of equality or maximizing the good or whatever the market produces or something else. The key point is that one might hold that current generations should devote resources to current generations in preference to future generations because of the distributive principle one affirms.

C.Risk and Uncertainty. The considerations adduced so far do not exhaust the reasons why one might devote resources to current generations over future generations. Two additional reasons to do so arise from each generation's lack of sure knowledge of future generations. First, we lack sure knowledge of the impacts of climate change. Second, we lack sure knowledge that human life will continue to exist. For example, the Stern Review on The Economic of Climate Change discounts by 0.1 percent per annum to reflect the possibility that humanity might die out for nonclimate-related reasons.15 Clearly, it matters what changes to the environment (rising sea levels and temperature increases) occur and how likely each possible scenario is. It also matters if humanity disappears because of some nonclimate-related calamity. If humanity dies out for nonclimate-related reasons, then one reason for being concerned about climate change (its impact on human life) no longer applies.16 Now if, for either reason, one is not certain that there will be malign effects on human life then, so it might be argued, there is a case for discounting the amount which one is going to spend on preventing a calamity from possibly taking place.

Before proceeding further it is worth noting the distinction between “risk,” on the one hand, and “uncertainty,” on the other. Risk refers to cases where one identifies an outcome and can determine the probability that it will occur. Uncertainty, on the other hand, refers to cases where one identifies an outcome but is not able to determine the probability of its coming to pass.17 Both might give us reason for discounting, but they are importantly different. For example, if one has reliable probabilistic assessments to hand, then one can calculate the expected utility and makes one's decision on that basis. Where, though, we face uncertainty this course of action is unavailable to us.


Putting this together, then, we see that the extent to which people may devote resources to the present as opposed to the future is a function of the following four variables: (1) the legitimacy of pure time preference (may we accord less weight to their interests?); (2) the principles of intergenerational justice (what principles of justice govern the relations between people over time?); (3) the certainty of the harmful effects (will these dangerous changes happen?); and (4) the certainty of human existence (are we sure that what we are doing will result in threats to human beings?).

II. Pure Time Preference and Discounting

Let us now consider one factor in the social discount rate and analyze one common argument for prioritizing current generations over future generations that focuses on this one variable. The first argument to be scrutinized makes the following claim:

Argument 1: Current generations should prioritize current generations over the interests of future generations because it is permissible (and maybe even morally required) for current people to engage in pure time preference.

Argument 1 defends a positive pure time discount rate. If we accept it, it follows that current generations should spend less on mitigation and adaptation than if they adopt a zero pure time discount rate. In what follows I shall reject this view and defend an alternative.

Before I introduce the view to be defended, it is worth drawing attention to the possibilities. Some apply a zero pure time discount rate to all values. As was noted earlier, Pigou, Ramsey, Sidgwick, Stern, and others have argued for the correctness of this view. A second group has defended a positive pure time discount rate. What both views have in common is their assumption that one should treat all values in the same way. All values should be subjected to exactly the same (positive, negative, or zero) pure time discount rate.

A third position is, however, worth considering. This view adopts what might be termed a Scope Restricted Pure Time Discount Rate (or more simply, the Scope Restricted View). This applies a zero pure time discount rate to some values but not to others. Stated more fully, the Scope Restricted View has three features. First, it posits that there is a plurality of different values. Second, it affirms what I shall term the Rights Principle. This holds that persons have human rights to the protection of fundamental human interests from the threats posed by dangerous climate change. Climate change jeopardizes various human rights including, for example: (1) the right to life (since storm surges, flooding and freak weather events, and heat stress will all lead to human deaths); (2) the right to subsistence (since the increase in temperatures, increased flooding, and rising sea levels will lead to crop failure and therefore malnutrition); (3) the right to health (since climate change will lead to increased exposure to vector-borne diseases (like malaria) and water-borne diseases (like dengue and diarrhea); (4) the right to property (since flooding, sea-level rise, and freak weather events may destroy people's privately and collectively owned property); and (5) the right not to be subject to enforced relocation (since sea-level rises will force inhabitants of coastal settlements or small island states to move).18 The Rights Principle calls then for the nonviolation, and the protection, of these vital rights—all of which are threatened by dangerous climate change.19 There are a number of different ways of grounding these rights. I here assume that they are justified on the grounds that they protect vital human interests that are sufficient to generate duties on others.20

Now the third part of the view to be defended holds that a zero pure time discount rate should be applied to the Rights Principle, but it need not be applied to other political principles or values. Human rights that are jeopardized by climate change should thus be secured (with no discrimination against those further off in time), but other more marginal interests (like being able to travel to interesting countries, or, more generally, the interest in satisfying preferences) may be subject to a positive pure time discount rate. Current generations should then act so as not to bring about a state of affairs in which people in one hundred years' time are unable to exercise their rights, but might be allowed to weight future people's interests in preference satisfaction, say, less than current people's interest in preference satisfaction.

Note that my version of the Scope Restricted View is not committed to calling for (or rejecting) a positive pure time discount rate for other values such as preference satisfaction. It simply allows the possibility that that might be the case. My emphasis is more on the first part: We may not discount current and future people's vital rights if, when and because the threat to them from climate change is further off in the future.21

A. Thus far, I have described the Scope Restricted View but not defended the approach to pure time preference that it adopts. I now wish to motivate some support for the claim that the rights jeopardized by climate change should not be subject to a positive pure time discount rate and hence why Argument 1 fails. Let us consider then what reasons might support a zero pure time discount rate.

The most common argument is one originally presented by William Stanley Jevons and later defended by A. C. Pigou. In The Theory of Political Economy, Jevons writes: “To secure a maximum of benefit in life, all future events, all future pleasures or pains, should act upon us with the same force as if they were present, allowance being made for their uncertainty. The factor expressing the effect of remoteness should, in short, always be unity, so that time should have no influence.”22 Jevons's argument, then, is that the “maximum of benefit” requires not according greater weight to a unit of pleasure because it is nearer in time. To prefer a smaller unit of utility at t1 to a greater unit of utility at t2 would lead to a suboptimal level of utility. We find the same argument in Pigou's seminal The Economics of Welfare. It is on the basis of this argument that he concludes that pure time preference is a failure of rationality: in his words, “our telescopic faculty is defective.”23

Clearly, this argument will not provide a defense of the Scope Restricted View outlined previously. Moreover, even if we set this aside, the limitations of this argument are fairly clear. It presupposes a maximizing consequentialism and for very familiar reasons (its indifference to the distribution of goods and its insensitivity to individual rights) I think that that position is unacceptable. Indeed, the argument exemplifies and illustrates a deep flaw in any maximizing doctrine. Consider the situation of an individual who is born in the future. The Jevons–Pigou argument would provide such a person with greater protection than they would be afforded by a positive pure time discount rate. However, note that that outcome is not animated by a commitment to the individual per se. Jevons's and Pigou's argument does aid the condition of future people but it does so only indirectly. Its direct concern is with increasing the total amount of well-being and it happens that a zero pure time discount rate furthers that goal. It illustrates well Rawls's objection that utilitarianism treats each individual merely as “a container-person.”24 Given the problems with this argument, let us consider an alternative argument.

B. A second objection to Argument 1 appeals (at a general level) to the ideal of impartiality and then (more specifically) to the logic underlying the Rights Principle. Consider impartiality first. The ideal of impartiality insists that political decisions should not reward or penalize people on the grounds of personal properties that lack any fundamental moral relevance. It is on this basis that we hold that persons should not be discriminated against because of their race or gender or socioeconomic class. These factors do not correspond to any morally relevant features of persons. In the same way, however, it seems inappropriate to discriminate against a person simply because of their location in time, for that seems equally arbitrary. It may be appropriate to favor some in some circumstances—if they are more deserving or more needy or they some possess other morally relevant property—but simply being born further into the future is not one of these properties. Put the other way round: being born earlier in time is just not the right kind of property to justify favoritism.

To illustrate this point, we may consider Sidgwick's defense of a zero pure time discount rate for this exemplifies the kind of reasoning advocated by the impartiality argument. Sidgwick's argument appeals to what is of fundamental importance from a utilitarian point of view (namely, “utility”) and deduces the appropriate pure time discount rate from that. Given that all that matters is the promotion of utility, it follows that “the time at which a man exists cannot affect the value of his happiness from a universal point of view; and that the interests of posterity must concern a Utilitarian as much as those of his contemporaries.”25

This Impartiality Argument can similarly be applied to the reasoning underlying the Rights Principle. Consider again the fundamental tenets of the theory. The argument for the protection of core rights invokes an orthodox conception of rights (in my case Raz's “interest theory”).26 The latter ascribes rights to agents when this protects an interest that is sufficient to impose duties on others. This, note, makes no reference to time. All that matters is the possession of fundamental interests and the reasonableness of the demands made on others, where that might include how demanding those demands are, whether it is unfairly burdening people, and so on. Time is not a morally relevant consideration. The logic of the case for rights entails, therefore, that there should be a zero pure time discount rate for the protection of rights. Put otherwise, a theory of justice animated by the dignity of persons and respect for their interests contains in it no room for ascribing lesser protection of these rights for some than for others. This argument thus defends the application of zero pure time discount rate to the protection of rights.

Note, moreover, that the argument under scrutiny does not commit us to applying a zero pure time discount rate to any other values. It simply appeals to the rationale underlying rights and argues that these do not allow any pure time discounting. As such it is, of course, silent on what kind of pure time discount rate is appropriate for other values. In short, this argument justifies the Scope Restricted View defined earlier in this section (II.A).27


It would be useful at this point to take stock and to return to the case of climate change. I have defended a zero pure time discount rate for the protection of the human rights jeopardized by climate change. This is supported by the Impartiality Argument (and an examination of the rationale underlying rights). This conclusion has considerable importance for climate change because the latter jeopardizes key rights. Given that these should receive equal weighting throughout time this strengthens the case for an aggressive program of mitigation.

III. Economic Growth and Discounting

Let us now turn to a second type of argument for devoting resources to current people over future people. Consider the following common argument:

Argument 2: Future generations will be wealthier than current generations and it is therefore more appropriate for current generations to devote resources to their contemporaries rather than to future people. It follows that it would be wrong to mitigate on behalf of future generations when they will be much better off than us.28

This is not an argument for pure time discounting. It is an argument for thinking that even if those who are currently alive weight future people's well-being as equal in standing to that of their contemporaries, they should devote more resources to their contemporaries because current generations are worse off than future generations will be.29 It makes the case for what William Nordhaus calls “growth discounting.”30 Broken down into its constituent parts, this argument claims:

  • 1It is wrong to devote resources to future generations rather than to current generations if future generations are wealthier than current generations.
  • 2Future generations will be wealthier than current generations.


  • 3Other things being equal, it is wrong to devote resources to future generations rather than to current generations.

One response to this would be to dispute premise (2) and to challenge whether this would be the case even if there is dangerous climate change. Alternatively, one might query the certitude with which this argument pronounces that future generations will definitely be wealthier. Can we be that sure? Such confidence certainly seems unwarranted at the moment. Isn't there a risk that a global recession might leave some future generations worse off than the current one? If so, how does that affect the argument?31 I want, however, to focus on premise (1) and to argue that (1) relies on an implausible principle of intergenerational justice. Why would it be wrong to devote resources to future generations if they are wealthier than current generations?

A. Three reasons suggest themselves. First, of course, many welfare economists who subscribe to (1) will appeal to the principle of diminishing marginal utility.32 That is to say, they will start with a commitment to utilitarianism and then add that the marginal utility of each extra unit of wealth decreases the wealthier a person is. It follows from these two assumptions that, if future generations will be wealthier than current generations, then it is wrong to devote resources to future generations. Therefore, current generations can discount the resources to be devoted to future generations.

However, this argument is vulnerable to an obvious objection, namely that it fails to disaggregate within generations and hence tolerates outcomes in which some lead appalling lives.33 It succeeds only if we consider each future generation as an aggregate and if we do not distinguish, for example, between the future Africans and future Americans who are members of the same generation. Thus even if a future generation at t2 is very wealthy and much wealthier than the generation alive at t1 that can hide the fact that some are very badly off at t2 (and indeed are worse off than some of the poorest at t1). Once disaggregated in this way, the case for devoting resources to the present (which in this context means not pursuing mitigation on behalf of future generations) diminishes because by doing so we will be bringing into existence a state of affairs in the future in which some, perhaps many, are needlessly unable to enjoy the fundamental rights specified by the Rights Principle.

There are, however, more sophisticated arguments for (1) which avoid this problem. Consider, for example, the following two arguments:

The Ability to Pay Argument: This holds that justice requires that those with the most ability to pay should bear the burden of combating social ills. It follows from this that if future generations are wealthier then they should foot the bill for combating climate change. In virtue of their wealth, they can bear the burden more easily than current generations.

The Cost-Effectiveness Argument: This holds that we should distribute resources in the most cost-effective manner. If future generations are wealthier then they have a greater ability to save lives than do current generations. Therefore, they, rather than current generations, should pay because by doing so they can achieve more good.34

These arguments are subtly different. The Cost-Effectiveness Argument is concerned with the number of lives saved and says that deferring the effort to combat climate change to later generations would be desirable because by doing so we can save more lives. The Ability to Pay Argument, by contrast, is not committed to the claim that deferring the effort until later saves more lives. It claims that it is fairer to any would-be duty-bearers to postpone efforts till later.35 Its focus is on the putative duty-bearers (it is wrong to burden X if Y is wealthier); whereas the focus of the Cost-Effectiveness Argument is on the recipients of any program designed to combat climate change, and more generally secure people's rights (it is wrong for humanity to try to help group (A) now when humanity could help group (A+100) later).

Both the Ability to Pay Argument and the Cost-Effectiveness Argument are better arguments than the preceding utilitarian one because, unlike it, they are not necessarily indifferent to the protection of human rights, including those rights specified by the Rights Principle. Proponents of both can be concerned with ensuring that everyone has a guaranteed decent standard of living. Both are nonetheless unconvincing.

B. Consider first the Ability to Pay Principle Argument. This encounters several problems. First, as I have argued at greater length elsewhere, the problem with relying on this principle to attribute responsibilities is simply that it conflicts with a very deep conviction that polluters should generally pay for their acts of pollution.36 If, for example, I leave rubbish in the street then, ceteris paribus, I have primary responsibility to clear it up—not some other actor who happens to have more wealth than me. Similarly, if my firm releases toxic waste into a river thereby harming others, we have a strong conviction that my firm should be held accountable for this—and not another firm that is wealthier. The view that the polluter should pay is one that is deeply rooted in our moral convictions and it follows from the principle that agents should be held responsible for their ends.

Suppose, though, that we accord some role to the Ability to Pay Principle, a second complication with the argument is that accepting the Ability to Pay Principle does not entail that we should allocate all of the burden associated with this role to future generations. Even if future people are, as an aggregate, wealthier than the current generation, there are, no doubt, some who are currently alive who are much wealthier than many future people will be. So an Ability to Pay Principle would require them to bear a burden in proportion to their wealth. Rather than allocate all responsibilities to future generations, it would endorse a scheme in which some wealthy current people pay and some poor future people do not. (Note, of course, that this second response cannot show that all growth discounting is impermissible. It simply establishes that the responsibility cannot be attributed entirely to future generations—but, for all that it says, it is compatible with thinking that some of it should be borne by contemporaries. As such, it is compatible with the current generation attributing some priority to [some] contemporaries.)

There are, however, deeper problems with the Ability to Pay Argument. That many future people will be wealthier than many of those who are currently alive does not entail postponing the effort to combat climate change later for two further reasons. First, obviously the cost of tackling the problem may—indeed almost certainly, will—increase and might increase by more than the increase in wealth. It is a nonsequitur to affirm that since a generation at t2 is wealthier than a generation at t1, it follows that the t2 generation should address the problem. Furthermore, the economic evidence strongly suggests that the rate of growth of the cost will exceed the rate of growth of global GDP. The appeal of an Ability to Pay Principle is that by allocating the tasks to the most advantaged it both enables a task to be performed and ensures that the duty-bearers are more able to pursue their own ends and goals. If, however, the costs of the task increase at a greater rate than the level of wealth increases, then the rationale of the Ability to Pay criterion is not served. If one is concerned that duty-bearers have a space to pursue their own projects, then it may be better to allocate the task to those with less wealth if the cost of the task to them is commensurately lower.

A final limitation in the Ability to Pay Argument is that it is incomplete. It is concerned only with what one might term the “duty-bearer perspective”—and with ensuring that the correct potential duty-bearer is allocated the responsibility. As such, it alone is unable to show that the duty should be allocated to future generations. For we also need to know whether they will do the job effectively. Suppose that if the job were done at t1 it would be done more effectively than it would be if it were done at t2. This would give us a reason to tackle it sooner rather than later and therefore to burden earlier generations rather than later ones. The point is simply that being fair to the duty-bearers is not the only relevant consideration—being fair to the recipients of the policy also matters. This leads us to the third argument for premise (1).

C. For consider, now, the Cost-Effectiveness Argument. Does this give us reason to devote our resources to current generations in preference to future ones? There are four reasons to resist this conclusion. First, the argument overlooks the obvious fact that tackling a problem earlier can be much cheaper than tackling it later. So even if future people have more wealth that does not mean it is right to defer tackling the problem to them because that advantage might be outweighed by the fact that the cost of “solving the problem” may cost even more. The Stern Review makes precisely this argument in support of its claim that current resources should be dedicated to combating climate change now.37

There is, moreover, a particular problem with postponing action on climate change that merits attention. Climate scientists have argued that greenhouse gas emissions may set in train irreversible processes that subsequently impact on future generations. Humanity may reach a “tipping point,” and after this it will not be possible to avert dangerous climate change. This arises because climate change may generate positive feedbacks which bring about additional climate change. Climate change becomes a self-reinforcing process. A recent review by David Frame and Myles Allen, climate modelers based at Oxford University, helpfully identifies six possible positive feedbacks. These include: (1) the release of methane from hydrates in the oceans (sometimes referred to as the “cathrate gun hypothesis”); (2) the release of methane from permafrost as the latter melts; (3) the loss of tropical forests, and in particular, the Amazon (and therefore the loss of their capacity to serve as carbon sinks); (4) an increase in ocean acidification which in turn destroys phytoplankton and thereby undermines the ability of oceans to absorb carbon dioxide; (5) the slowing down of the Atlantic Thermohaline Circulation (ATC); and (6) increases in water vapor which augment the warming effect.38 To attribute the responsibility to later generations may then to be to leave it until it is too late.

A further weakness in the Cost-Effectiveness Argument is that its focus is solely on the capacity of future generations to achieve more. However, before we, the current generation, create a situation in which there will be winners and losers in the future, we also need to know whether those who will be very wealthy in the future will use that capacity to protect the most vulnerable from dangerous climate change and uphold their fundamental rights. We need, that is, to know what they will be disposed to do as well as what they can do. Moreover, given the historical record, we can hardly be confident that in creating a world with a very wealthy group we will be creating a group who are properly motivated to protect the fundamental human rights of all, including the most vulnerable. In light of this, it would, I think, be irresponsible of powerful decision-makers in one generation not to mitigate climate change in the hope that the world they create will be one in which a wealthy component secures the fundamental rights of all from the threats of climate change. Anyone motivated by a commitment to fundamental human rights would not gamble in this way with the plight of those alive in the future.

A fourth, and final, point should now also be duly noted. I argued above that the Ability to Pay Argument is incomplete. For a parallel reason, the same is true of the Cost-Effectiveness Argument. Suppose that we show that future generations are more effective at solving problems. This does not entail that the future generations ought to address the problem for we need also to consider the duty-bearer perspective. If, for example, justice requires that those responsible for causing a problem should pay, then contemporary polluters should pay and it is unfair on later generations to attribute this duty to them. It is important not only that people's entitlements are protected but also that the burden of protecting these entitlements is fairly distributed.

In short, none of the three arguments support premise (1) of Argument 2. Each fails, in different ways, to protect the fundamental rights that are jeopardized by anthropogenic climate change. The Diminishing Marginal Utility argument focuses exclusively on aggregate outcomes and is therefore quite compatible with permitting policies which threaten the fundamental rights of some; the Ability to Pay Argument is focused solely on who should bear the duty of combating climate change and therefore it too ignores the question of whether allocating this duty to future generations will result in the protection of persons' fundamental rights from the threats posed by climate change; and the Cost-Effectiveness Argument is motivated by a concern to protect the rights of the vulnerable, but it overlooks the tremendous costs involved in postponing action until later.

D. Let us suppose that the concerns raised in section C are all met. Suppose that we know that future people will be much wealthier (they can pay); suppose that the Ability to Pay Principle is correct and it is right to allocate the responsibility to combat climate change to them (they ought to pay); and suppose, finally, that we know that the wealthy people in the future will be disposed to protect the fundamental rights of all from the threats posed by climate change (they will pay). Even so, Argument 2 fails because it makes the questionable assumption that greater wealth can counterbalance the threats posed by the worsening climate that we the current generation help to produce.

Why should we accept this assumption? One might give two arguments for it.39 The first contends that greater economic wealth enables people to adapt and thereby avert the ill-effects of climate change. Let us term this the Adaptation Response. The second reason one might think that economic growth counterbalances a deterioration in the climate is that one thinks that people might be unable to adapt to the change but that the money can serve as compensation for the loss. Let us call this the Compensation Response.40

Both arguments for why economic growth matters fail. The problem with the first is that it is unduly sanguine about the effectiveness of adaptation. It assumes that if money is available and deployed to further adaptation then the rights of those threatened by climate change are secure. This overlooks several critical problems. First, although climate scientists understand the general processes of climate change, they are often unable to specify what changes will happen to which specific areas. Preparing for adaptation is therefore very much an imperfect science. Furthermore, adaptation requires not simply resources but accountable governance structures, ones in which political elites are responsive to people's need for protection from environmental threats, and greater wealth on its own cannot bring this about. Consider in this light those living in authoritarian and corrupt political systems—there can be no assurance that financial support will reach the vulnerable areas. In addition to this, even if we know where climate-related threats will occur and even if political elites are responsive to the needs of their people, adaptation policies (such as building dykes, having better drainage systems, and so on) are not fool-proof and thus cannot be relied upon to prevent any harms arising from climate change. The Adaptation Response fails.

Consider now the Compensation Response. This accepts that adaptation may not suffice and hence that climate change may violate certain key rights. But it adds that this is acceptable if the victims of the violation of these rights are compensated in monetary terms.

This argument also fails. Rights entail duties on others not to violate them and if others do violate them then, other things being equal, they are under a duty to compensate those wronged. What is generally impermissible is deliberately to violate a right with a view to compensating people for it. One cannot assault someone and then make it up to them by paying for their hospital bills and fully covering all aspects of their recovery. The point is that one should not inflict that wrong in the first place: it is impermissible to inflict the bad with a view to creating a good to make up for this.41 It misunderstands the nature of a right to choose to violate it when one has the option of not doing so.42 There are, of course, exceptional cases where this is permissible, but the point is that these arise in emergencies. In normal policy-making rights are not to be violated, and certainly not when there are other morally acceptable courses of action available.43

Thus, neither the Adaptation Response nor the Compensation Response can show that economic growth can offset the threats posed by climate change. Argument 2's claim that current generations should not mitigate climate change on the grounds that future generations will enjoy higher average wealth and that this economic growth counterbalances the resulting dangerous climate is thus further undermined.

IV. Risk, Uncertainty, and Discounting

Let us now consider a third reason for discounting. One argument often given in defense of discounting the amount of resources to be devoted to a problem is that the projected harms may not materialize or that we are uncertain about their likelihood. As was noted earlier, the projected changes to the Earth's climate involve both risks and uncertainties. The IPCC, for example, lists various impacts and then assigns rough probabilities to each. In addition, some phenomena are more accurately described as uncertainties (that is, we cannot formulate a reliable probability for them).44 These risks and uncertainties lead then to the following argument:

Argument 3: Since climate change is projected to result in risks (i.e., outcomes with a probability of less than one) and/or uncertainties (i.e., outcomes whose probability cannot be ascertained), current generations should discount future impacts and should, therefore, devote current resources to their contemporary problems rather than to future ones.

A. Argument 3 would be advanced by advocates of Cost-Benefit Analysis (CBA). On this view, we should multiply the cost or benefit of an outcome by the probability of its occurring. Any probability less than 1 is a form of discounting. This approach does have intuitive appeal. If we cannot be sure whether a bad event will occur, or if we know that the probability of it occurring is less than one, then it seems natural to devote less resources to combating that problem than we would if we knew that the bad event would definitely occur.

In what follows I shall argue, however, that we should reject Argument 3. I maintain that the fact that statements about the harmful effects of climate change refer to risks and uncertainties, rather than definitely known impacts, does not justify paying less of a cost. A sound response to the current climate change, I suggest, would prescribe exactly the same course of action (in terms of the money spent) to mitigating climate change as would be appropriate if it were known that the malign effects would definitely occur. To put it another way round, I shall defend a precautionary approach to climatic risks and uncertainties. However, rather than appeal to a version of the precautionary principle in the premises that follow, I shall adduce four considerations which are jointly sufficient to entail a precautionary conclusion.45

First, though, let us consider CBA. Applying CBA to climate change is problematic for two reasons. The first is that CBA requires probabilistic assessments in order to calculate the expected utility for any event, but it is at a loss when we face uncertainties. And, as many have observed, it is extremely hard to ascertain with any precision or confidence the probabilities of many of the specific impacts caused by climate change.46 Second, and more fundamentally, this way of thinking about risk seems inappropriate in this context. CBA may be applicable in the context of one person's life. If I am considering taking a grave risk and I alone will bear its potential burden then it might seem appropriate for me to consider the issue simply in terms of the expected costs and expected benefits to me. However, it is inappropriate to adopt this model when we are considering cases where some (high emitters who are affluent) are exposing others to grave risks and jeopardizing their rights. The interpersonal context makes all the world of difference. The principles applicable within the context of one life are not the same as those applicable across lives.47

Under what conditions, if any, is it fair for one group to expose another group to risks? Two different kinds of approach are available, both of which invoke rights. One answer takes a procedural form. It holds that exposing some to risks can be just if the risk-bearers have a genuine choice (for example, they have the right to veto the proposal and can do so without inappropriate repercussions) and they consent to being exposed to risk. They might, for example, accept the risk if they can share in the benefits of the risky activity and/or if they are guaranteed adequate compensation if the possible hazards materialize. This procedural route is, however, not available to us given that some of the risk-bearers have yet to be born and some are but infants now. So we have reason to consider a second type of approach—a substantive approach that focuses on whether the distribution of burdens and benefits is fair according to some substantive criteria.

In light of this one might seek to develop a comprehensive theory of when exposing others to risks is just and then apply that to climate change. Such a theory would provide the necessary and sufficient conditions for imposing risks on others, and by doing so would develop a theory of “fair risk” that is applicable for all situations. That would be a very ambitious project. It is also unnecessary for our purposes—which are to examine whether it is justified to discount the impacts of climate change because of the uncertain nature of climate projections. In what follows I shall therefore pursue a more modest task, and will identify several conditions which both apply specifically to the current changes to the climate and provide guidance on the legitimacy of discounting.

B. The following line of reasoning will, I believe, show that it is unjust for the world's highest per capita emitters to expose others to the risks associated with dangerous climate change. Moreover, they should not discount the projected ill-effects on the grounds that they are merely risks and uncertainties. Why should we adopt such a cautious approach to global climate change? The following four rights-centered considerations, I think, provide a conclusive answer.

(R1) The changes to the climate involve both (a) a high probability of severe threats to large numbers of persons' fundamental human rights and (b) a possibility of even more catastrophic threats to fundamental human rights.

First, note that the IPPC's reports differentiate between seven different categories of probability—ranging from “virtually certain” (>99%), “very likely” (90–99%), and “likely” (66–90%) at one end of the spectrum to “very unlikely” (1–10%) and “exceptionally unlikely” (<1%) at the other.48 They maintain that many of the dangerous changes to the Earth's climate are “likely” or “very likely.” The Fourth Assessment Report, for example, concludes that in the twenty-first-century droughts, more frequent intense cyclones and extreme sea-level rises are “likely”; that heatwaves and extreme precipitation are “very likely”; and that increased temperatures are “virtually certain.”49 If we turn now to the projected impacts on human rights, the IPCC reports maintain that climate change will lead to loss of life, exposure to disease and malnutrition. It distinguishes between different levels of confidence, ranging from “very high confidence” (“at least 9 out of 10 chance of being correct”) and “high confidence” (“about 8 out of 10 chance”) to “very low confidence” (“less than a 1 out of 10 chance”).50 And many of its projections of dangerous threats to fundamental human interests are ones which it categorizes as “high confidence.” To take one example, the IPCC's chapter on human health has “high confidence” that climate change will lead to (1) “increased malnutrition”; (2) an increase in “the number of people suffering from death, disease and injury from heatwaves, floods, storms, fires and droughts”; and (3) increased “cardio-respiratory morbidity and mortality.”51

Consider now (b). In addition to the prospects of drought, flooding, sea-level rise, and freak weather events, there are possible effects which, if they occurred, would be catastrophic, but the probability of them occurring is very low. Three phenomena in particular are worth mentioning here. First, there is a possibility that the Greenland Ice Sheet will melt, thereby raising sea levels by seven meters.52 Second, it is also possible that the West Antarctic Ice Sheet will melt. According to Michael Oppenheimer and R. B. Alley, this alone would increase sea levels by approximately five meters.53 Both of these would be calamitous: They would devastate the rights to life, health, and subsistence of inhabitants of small-island states and all those who live or work on the coast. A third possibility which is related to, but distinct from the preceding two, is the slowdown or collapse of the ATC. This too is unlikely but if it occurred it would have considerable impact, including reducing temperatures in Europe.54 According to Michael Vellinga and Richard Wood, both scientists at the Metereological Office in London, the collapse of the ATC may lead to a drop in temperatures in Europe of between 1 and 3°C.55 These three phenomena illustrate then the possibility of abrupt nonlinear climate change.56

Note, however, that in itself (R1) is insufficient to ground a policy of precaution. That one course of action has grave—even catastrophic—risks attached to it does not entail that one should eschew it, for the other options available might also have equally grave risks.57 This leads to my second point. For the second step in my argument is that:

(R2) Affluent members of the world can abstain from emitting high levels of greenhouse gases, and thereby exposing others to risk, without loss of their own human rights.

(R2) is supported by two considerations. First, many affluent people expend energy on activities which might have value but are not needed for the realization of people's human rights, and can therefore be foregone without sacrificing their rights. Consider, in this context, the emissions stemming from driving cars, taking plane flights, poorly insulated housing, and inefficient energy use. Cuts from all of these are needed to avoid dangerous climate change, but the loss involved cannot be said to compromise any human rights. Second, affluent people in the industrialized world are also able to engage in some activities to which they have a human right, without employing the fossil fuels that they currently use. For many the right to a decent minimum standard of living (which entails rights to heating) can be met without exposing others to risk—if, for example, they use renewable energy sources rather than fossil fuels. For both of these reasons affluent members of the world can abstain from exposing others to risks without the loss of their own human rights. It might be true that mitigating climate change and funding adaptation will be costly (though we should bear in mind the statistic quoted earlier from the Stern Review [p. 3]), but these costs do not involve a loss of human rights and, as such, cannot compete with the priority to protecting people's human rights articulated by (R1).

These two considerations alone might be thought sufficient to ground a precautionary approach.58 In case there is any doubt, two additional supplementary considerations further consolidate the case for holding that the high emissions of the affluent is unjust. Consider now:

(R3) The risks of dangerous climate change will fall disproportionately on those whose human rights are already violated.

There is consensus among climate scientists and environmental economists that anthropogenic climate change will have particularly severe effects on people who already lack fundamental human rights. Disease, malnutrition, and poverty are already rife in Africa and climate change risks making it even worse. Furthermore, sea-level rise will impact heavily on the members of Bangladesh—who currently lack fundamental subsistence and health rights. For affluent persons and corporations to engage in a Business as Usual approach would therefore be for them to gamble with the condition of those who already lack fundamental rights protection, threatening to render them even worse off.59

The case for affluent emitters to cut their emissions so as not to expose others to grave risks is strengthened further if we note one additional feature of the current situation:

(R4) The benefits that arise when the affluent of the world emit high levels of greenhouse gases falls almost entirely to them, and not to those most at risk from climate change.

It is arguable that for some to expose others to risk can be morally acceptable if the risk-taking is part of an equitable scheme. To use a familiar example, one might think that it is permissible for some to drive motor vehicles even though they pose a fatal threat to some because the risky activity is part of an equitable scheme which is generally beneficial, including to the risk-bearers. Even nondrivers might value the practice of driving—it means that their friends and family can visit, goods can get transported promptly from one end of the country to another, food gets delivered to shops still fresh, business and personal correspondence can arrive swiftly, and so on.60 Now the point of (4) is simply to add that no such argument can be made in defense of the current emissions of the world's wealthy—because the benefits redound almost entirely to the risk-takers and not the risk-bearers.

In short, the preceding argument holds that it is wrong for some to engage in activities which are likely to violate the human rights of others (and might lead to a catastrophic outcome) in situations where the risk-takers need not engage in the risky behavior and can avert it without forfeiting their own human rights, when the risk-bearers already lack fundamental human rights, and when the benefits of the risky behavior fall to the risk-takers and not the risk-bearers.

C. What does this mean for the social discount rate? I think the answer here is that it is wrong to discount potential harms to others on the grounds that the likelihood of their impact is either less than one or it is unknown. The implication of the argument given previously is that the affluent should simply abstain from the risky behavior in cases where (R1)–(R4) apply. It is not that they should carry on with the reckless activity but do it less often. They should desist entirely. They should act in exactly the same way and bear exactly the same cost (the opportunity cost of not engaging in the risky behavior) as if it were known beyond doubt that the harmful impacts would materialize. If, however, this is the case the upshot is that there should be zero discounting for risk. It makes no difference to the assessment if the probability is one hundred or eighty-five percent, say.61

D. Three further points bear noting. First, note that the argument presented previously—like the arguments in sections II and III—is grounded in a commitment to human rights. Human rights are invoked in three places. (R1) invokes the fact that there is a threat to people's human rights; (R2) states that the cost of not violating people's human rights does not itself involve a loss of rights; and (R3) draws attention to the fact that many of those most vulnerable to the risky activities already lack fundamental rights. Second, note that my claim is that (R1)–(R4) are sufficient to ground a no-discounting conclusion. To assert this is not to claim that some other conditions (maybe weaker versions of (R1)–(R4) or maybe some other combination) may not also be sufficient to ground this conclusion. Maybe they are. My point is simply that the factual conditions are those described by (R1)–(R4) and that given these we should accept the conclusion I urge. Note too that my argument does not claim that (R1)–(R4) are necessary to ground the no-discounting conclusion. Third, in the preceding analysis I have deliberately focused on the responsibilities of affluent emitters. One interesting and important implication of the argument relying on (R1)–(R4) is that it does not show that all agents should observe the “precautionary” principle. The reason for this stems from (R2), which focuses on the advantaged and argues that they can avoid the risky behavior without suffering an undue loss. However, many of the citizens of countries like China and India are in a different position. It is not true of them that can they abstain from exposing others to risk without loss of their human rights. For them to adopt a precautionary approach would be for them potentially to jeopardize their fundamental rights. As such, it is arguable that they are entitled to engage in the emissions necessary to their fundamental rights even if by doing so they contribute to dangerous climate change.62 If the choice they face is between not surviving and acting in such a way that exposes others to severe risks, then they have a case for emitting the greenhouse gases necessary to achieve a basic minimum (though this might, of course, depend on the numbers involved).63

V. Conclusion

Climate change jeopardizes fundamental human rights. I have argued that seeing climate change in this way helps us to address the intergenerational challenges posed by climate change. In particular, I have

  • 1rejected a uniform positive pure time discount rate and defended a distinctive approach to pure time discounting, arguing that a zero pure time discount rate should be applied to the Rights Principle but it need not be applied to other values;
  • 2rejected the argument that we may discount the interests of future generations because they will be wealthier, and argued that this does not respect the fundamental rights of future people; and
  • 3rejected the argument that risk and uncertainty justify discounting. When we bear in mind the interpersonal nature of the situation and the rights of the risk-bearers, we should conclude that the advantaged should not expose the vulnerable to the possibility of further rights violations.

A human rights-oriented approach can thus provide guidance on how to think about the social discount rate. Furthermore, it gives us good reason to reject “time” discounting, “growth” discounting, and “risk and uncertainty” discounting. As such, it strengthens the case for an aggressive policy of mitigation and adaptation dedicated to preventing rights-jeopardizing climate change.

This paper was presented at the “Justice and Boundaries” Conference, University College Dublin (May 2, 2008), the Conference on “Human Rights and Global Law,” University of Palermo (June 3–8, 2008), the CSSJ seminar (October 27, 2008), and the political theory seminar at the University of Gothenburg (November 29, 2008). Parts of the paper draw on a paper given at Amsterdam University (March 22–23, 2007), University of Washington (May 3–4, 2007), and University of Oslo (June 21–24, 2007). I thank the participants for their questions and objections. I am particularly grateful to John Barry and Göran Duus-Otterström (my respondents at Dublin and Gothenburg, respectively), and to Paul Baer, Alan Carter, Steve Gardiner, Tim Hayward, David Miller, Dominic Roser, and Isabel Trujillo for helpful comments and discussion. The first draft of this paper was written during my tenure of a Leverhulme Research Fellowship and work on it was completed during my tenure of an ESRC Climate Change Leadership Fellowship. I thank the Leverhulme Trust and the ESRC for their support.


  • 1

    David Hume, A Treatise of Human Nature (Harmondsworth: Penguin, 1985 [1739–40]), bk. III, pt. II, sec. VII, p. 590.

  • 2

    Susan Solomon, Dahe Qin, and Martin Manning, “Technical Summary,” in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. Susan Solomon et al. (Cambridge: Cambridge University Press, 2007), 70. It is important to bear in mind that the sea-level projections exclude “future rapid dynamical changes in ice flow.”

  • 3

    See Simon Caney, “Human Rights, Responsibilities and Climate Change,” in Global Basic Rights, ed. Charles Beitz and Robert Goodin (Oxford: Oxford University Press, 2009), 227–47; and Simon Caney, “Climate Change, Human Rights and Moral Thresholds,” in Human Rights and Climate Change, ed. Stephen Humphrey (Cambridge: Cambridge University Press, forthcoming 2009). See also Tim Hayward, Constitutional Environmental Rights (Oxford: Oxford University Press, 2005) for a defense of a “human right to an adequate environment” (especially chapter 1).

  • 4

    Sir John Houghton, Global Warming: The Complete Briefing, 3rd ed. (Cambridge: Cambridge University Press, 2004), 30–31.

  • 5

    Bjørn Lomborg has famously argued that the resources devoted to mitigating climate change could be better spent elsewhere. See Bjørn Lomborg, The Skeptical Environmentalist: Measuring the Real State of the World (Cambridge: Cambridge University Press, 2001), 322–24; and also the views of the panel of experts reported in Bjørn Lomborg, ed., Global Crises, Global Solutions (Cambridge: Cambridge University Press, 2004), 605–44.

  • 6

    The social discount rate has been widely ignored by philosophers. For a rare example, see the illuminating discussion of discounting by Derek Parfit in Reasons and Persons (Oxford: Oxford University Press, 1986), 480–86.

  • 7

    See Alfred Marshall, Principles of Economics, 8th ed. (London: Macmillan, 1961 [1920]), bk. III, chap. V, sec. 3–4, pp. 119–23; A. C. Pigou, The Economics of Welfare, 4th ed. (London: Macmillan, 1946), 24–30; Frank Ramsey, “A Mathematical Theory of Saving,”Economic Journal 38, no. 152 (1928): 543–59; and Sir Nicholas Stern, The Economics of Climate Change: The Stern Review (Cambridge: Cambridge University Press, 2007), esp. 35–37 and 50–60.

  • 8

    In what follows I shall refer frequently to “future generations.” Note, of course, that a social discount rate has a bearing not simply on those who have not been born but also on those who are currently alive who will remain alive for several years to come. It bears on what resources we devote to people's interests in the future where that includes people who are already alive and those who will be born by then. It would be cumbersome to make this point repeatedly and so for simplicity's sake I will refer to future generations.

  • 9

    Stern, The Economics of Climate Change, 239.

  • 10

    Eric Neumayer, “A Missed Opportunity: The Stern Review on Climate Change Fails to Tackle the Issue of Non-substitutable Loss of Natural Capital,”Global Environmental Change 17, nos. 3–4 (2007): 300.

  • 11

    Pigou, The Economics of Welfare, 24–30; Ramsey, “A Mathematical Theory of Saving,” 543; and Stern, The Economics of Climate Change, 35.

  • 12

    R. F. Harrod, “The Supply of Saving,” in Towards a Dynamic Economics: Some Recent Developments of Economic Theory and Their Application to Policy (London: Macmillan, 1949), 40.

  • 13

    Ibid., 37.

  • 14

    Henry Sidgwick, The Methods of Ethics, 7th ed. (Indianapolis, IN: Hackett Publishing Company, 1981 [1907]), bk. IV, chap. 1, sec. 2, p. 414.

  • 15

    Stern, The Economics of Climate Change, 53 and 663.

  • 16

    Even if humanity dies out one might have other very considerable reasons to avert dangerous climate change. One might have moral reasons stemming from a concern for the natural world and the lives of nonhuman animals. I endorse these other reasons but want to focus here on the impact of climate change on human beings.

  • 17

    I here follow Frank Knight's seminal discussion in Risk, Uncertainty, and Profit (Boston and New York: Houghton Mifflin Company, 1921), esp. 19–20 and 197–232.

  • 18

    For excellent empirical data on the impacts of climate change, see Martin Parry, Osvaldo Canziani, Jean Palutikof, Paul van der Linden, and Clair Hanson, eds., Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press, 2007); and Hans Joachim Schellnhuber, Wolfgang Cramer, Nebojsa Nakicenovic, Tom Wigley, and Gary Yohe, eds., Avoiding Dangerous Climate Change (Cambridge: Cambridge University Press, 2006).

  • 19

    Some, of course, deny that future people have rights. For an argument defending the ascription of rights to future persons, see Caney, “Human Rights, Responsibilities and Climate Change,” sec. I.

  • 20

    For an argument to this effect, see Caney, “Climate Change, Human Rights and Moral Thresholds.” My account is indebted to Raz's articulation of the interest theory of rights. See Joseph Raz, The Morality of Freedom (Oxford: Clarendon Press, 1986), chap. 7 in general and p. 166 in particular.

  • 21

    Note there are other different kinds of Scope Restricted View. See, for example, that defended by Avner de-Shalit, Why Posterity Matters: Environmental Policies and Future Generations (London: Routledge, 1995), 13–14, 54–55, and 62–65.

  • 22

    William Stanley Jevons, The Theory of Political Economy, 2nd ed. (Harmondsworth: Penguin, 1970 [1879]), chap. III, p. 124.

  • 23

    Pigou, The Economics of Welfare, 25; cf. also pp. 25–26.

  • 24

    Rawls, “The Independence of Moral Theory,”Proceedings and Addresses of the American Philosophical Association 48 (1974–75): 17. The point is also made in “Reply to Alexander and Musgrave,”Quarterly Journal of Economics 88, no. 4 (1974): 645.

  • 25

    Sidgwick, The Methods of Ethics, 414.

  • 26

    See note 20.

  • 27

    I have argued elsewhere that this Scope Restricted View is also not vulnerable to various objections leveled against zero pure time discount rates: Simon Caney, “Climate Change, Human Rights and Discounting,”Environmental Politics 17, no. 4 (2008): 548–50.

  • 28

    For this viewpoint see Lomborg, The Skeptical Environmentalist, 314; William Nordhaus, “Discounting in Economics and Climate Change,”Climatic Change 37, no. 2 (1997): 317; William Nordhaus, “The Question of Global Warming: An Exchange,”New York Review of Books 55, no. 14 (September 25, 2008): 93.

  • 29

    Robert M. Solow gives voice to this thought when he writes: “In social decision-making, however, there is no excuse for treating generations unequally, and the time-horizon is, or should be, very long. In solemn conclave assembled, so to speak, we ought to act as if the social rate of time preference were zero (though we would simultaneously discount future consumption if we expect the future to be richer than the present).” See Robert M. Solow, “The Economics of Resources or the Resources of Economics,”American Economic Review 64, no. 2 (1974): 9.

  • 30

    Nordhaus, “Discounting in Economics and Climate Change,” 317.

  • 31

    Issues of risk and uncertainty are addressed in the next section.

  • 32

    See, for example, Harrod, “The Supply of Saving,” 38ff.

  • 33

    For instructive discussions of the importance of disaggregating groups when considering discount rates, see Thomas Schelling, “Intergenerational Discounting,”Energy Policy 23, nos. 4/5 (1995): 398–400; and Thomas Schelling, “Intergenerational and International Discounting,”Risk Analysis 20, no. 6 (2000): 835–36.

  • 34

    For a similar type of argument, see Dan Moller, “Should We Let People Starve—For Now?”Analysis 66, no. 291 (2006): 240–47. His argument is not concerned with climate change but with the case for poverty relief but does have a similar (but nonidentical) structure.

  • 35

    I am assuming that if we require future generations to bear the burden of combating climate change, then the policies employed to combat climate change will, correspondingly, take place in the future. That is, I am ruling out the possibility that the policy enacted to combat climate change is implemented in t1 and the bill for doing so is somehow picked up by future people at time t100, say. I am grateful to Vijay Joshi and Andrew Williams for comments on a quite different paper which drew attention to this issue.

  • 36

    There are, of course, exceptions to this. For example, I think it is unfair to make polluters pay if making them do so pushes them beneath a decent minimum standard of living and thus I affirm a poverty-sensitive Polluter Pays Principle. For further discussion, see Simon Caney, “Climate Change, Justice and the Duties of the Advantaged,”Critical Review of International Social and Political Philosophy 12, no. 2 (forthcoming 2009); and Caney, “Human Rights, Responsibilities and Climate Change.” I argue there that Ability to Pay considerations should play a subsidiary role.

  • 37

    Stern, The Economics of Climate Change.

  • 38

    See David Frame and Myles R. Allen, “Climate Change and Global Risk,” in Global Catastrophic Risk, ed. Nick Bostrom and Milan M. Ćirković (Oxford: Oxford University Press, 2008), 273–75. John Houghton also discusses positive and negative feedbacks in Global Warming: The Complete Briefing, 35, 39–40, 90–95, and 186. Edward A. G. Schuur and his coauthors have also argued that the melting of permafrost will result in the release of billions of tons of carbon into the atmosphere: see Edward A. G. Schuur et al., “Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle,”Bioscience 58, no. 8 (2008): 701–14.

  • 39

    There is a longstanding debate about whether economic growth can offset the loss of environmental natural capital. For an important account, see Andrew Dobson's discussion of different conceptions of sustainability in Justice and the Environment: Conceptions of Environmental Sustainability and Dimensions of Social Justice (Oxford: Oxford University Press, 1998).

  • 40

    There is, of course, a third response, namely that the economic growth counterbalances the threats to some caused by climate change because the evils suffered by some can be outweighed by the benefits to others. Given my affirmation of the Rights Principle, I set aside this utilitarian kind of response.

  • 41

    This point has been persuasively made by Henry Shue, “Bequeathing Hazards: Security Rights and Property Rights of Future Humans,” in Global Environmental Economics: Equity and the Limits to Markets, ed. Mohammed H. I. Dore and Timothy D. Mount (Malden, MA and Oxford: Blackwell Publishers, 1999), 40–42; and by Clive Spash, Greenhouse Economics: Value and Ethics (London and New York: Routledge, 2002), chap. 9, esp. pp. 231–36. Shue grounds his argument on the assumption that the rights in question are inalienable. In contrast to this, I hold that (1) it is not necessary to appeal to inalienable rights to ground this conclusion; and (2) the rights Shue posits (like the right to physical security) are not in fact inalienable (people may consent to others inflicting physical pain on them).

  • 42

    There is also the obvious but nonetheless important point that some (e.g., those who lose their life because of climate change) cannot be compensated.

  • 43

    A similar kind of point is sometimes made about natural phenomena of great value (e.g., glaciers or rainforests or coral reefs). The thought is that these goods are irreplaceable and their loss is irreversible. On this basis, one might argue that it is wrong to act in such a way that these places of great beauty are destroyed. For pertinent discussion, see Robert E. Goodin, Green Political Theory (Cambridge: Polity Press, 1992), 57–61; Eric Neumayer, Weak versus Strong Sustainability: Exploring the Limits of Two Opposing Paradigms, 2nd ed. (Cheltenham: Edward Elgar, 2003); and Neumayer, “A Missed Opportunity,” 299–301.

  • 44

    Moreover, as was noted in the previous section, there is also uncertainty about future economic growth and uncertainty about the motivations of the wealthy in the future.

  • 45

    There are many different versions of the precautionary principle. For some influential formulations of the precautionary principle, see Principle 15 of the Rio Declaration on Environment and Development ( and Article 3.3 of the United Nations Framework Convention on Climate Change ( For an instructive analysis, see Jonathan B. Weiner, “Precaution,” in The Oxford Handbook of International Environmental Law, ed. Daniel Bodansky, Jutta Brunnée, and Ellen Hey (Oxford: Oxford University Press, 2007), 597–612.

  • 46

    This point is emphasized by Stephen Gardiner, “Ethics and Global Climate Change,”Ethics 114, no. 3 (2004): 571–72.

  • 47

    My remarks here draw, of course, on Rawls's well-known claim that utilitarianism “does not take seriously the distinction between persons” (A Theory of Justice, rev. ed. [Oxford: Oxford University Press, 1999], 24). See also Robert Nozick, Anarchy, State, and Utopia (Oxford: Blackwell, 1974), 33.

  • 48

    Martin Parry, Osvaldo Canziani, and Jean Palutikof, “Technical Summary,” in Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. Martin Parry, Osvaldo Canziani, Jean Palutikof, Paul van der Linden, and Clair Hanson (Cambridge: Cambridge University Press, 2007), 27.

  • 49

    Solomon et al., “Technical Summary,” 52.

  • 50

    Parry et al., “Technical Summary,” 27.

  • 51

    Ulisses Confalonieri and Bettina Menne, “Human Health,” in Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. Martin Parry, Osvaldo Canziani, Jean Palutikof, Paul van der Linden, and Clair Hanson (Cambridge: Cambridge University Press, 2007), 393.

  • 52

    Jason A. Lowe, Jonathan M. Gregory, Jeff Ridley, Philippe Huybrechts, Robert J. Nicholls, and Matthew Collins, “The Role of Sea-Level Rise and the Greenland Ice Sheet in Dangerous Climate Change: Implications for the Stabilisation of Climate,” in Avoiding Dangerous Climate Change, ed. Hans Joachim Schellnhuber, Wolfgang Cramer, Nebojsa Nakicenovic, Tom Wigley, and Gary Yohe (Cambridge: Cambridge University Press, 2006), 30.

  • 53

    Michael Oppenheimer and R. B. Alley, “The West Antarctic Ice Sheet and Long Term Climate Policy,”Climatic Change 64, nos. 1–2 (2004): 2. For discussion of the West Antarctic Ice Sheet, see also Chris Rapley, “The Antarctic Ice Sheet and Sea Level Rise,” in Avoiding Dangerous Climate Change, ed. Hans Joachim Schellnhuber, Wolfgang Cramer, Nebojsa Nakicenovic, Tom Wigley, and Gary Yohe (Cambridge: Cambridge University Press, 2006), 25–27.

  • 54

    For discussion of the Atlantic Thermohaline Circulation, see Michael Vellinga and Richard A. Wood, “Global Climatic Impacts of a Collapse of the Atlantic Thermohaline Circulation,”Climatic Change 54, no. 3 (2002): 251–67. See also Michael E. Schlesinger, Jianjun Yin, Gary Yohe, Natalia G. Andronova, Sergey Malyshev, and Bin Li, “Assessing the Risk of a Collapse of the Atlantic Thermohaline Circulation,” in Avoiding Dangerous Climate Change, ed. Hans Joachim Schellnhuber, Wolfgang Cramer, Nebojsa Nakicenovic, Tom Wigley, and Gary Yohe (Cambridge: Cambridge University Press, 2006), 37–47; and Richard Wood, Matthew Collins, Jonathan Gregory, Glen Harris, and Michael Vellinga, “Towards a Risk Assessment for Shutdown of the Atlantic Thermohaline Circulation,” in Avoiding Dangerous Climate Change, ed. Hans Joachim Schellnhuber, Wolfgang Cramer, Nebojsa Nakicenovic, Tom Wigley, and Gary Yohe (Cambridge: Cambridge University Press, 2006), 49–54.

  • 55

    Vellinga and Wood, “Global Climatic Impacts,” 255.

  • 56

    For further pertinent discussion see Michael Oppenheimer and R. B. Alley, “Ice Sheets, Global Warming, and Article 2 of the UNFCCC,”Climatic Change 68, no. 3 (2005): 257–67; Stefan Rahmstorf and Kirsten Zickfeld, “Thermohaline Circulation Changes: A Question of Risk Assessment,”Climatic Change 68, nos. 1–2 (2005): 241–47; Stephen H. Schneider, “Abrupt Non-linear Climate Change, Irreversibility and Surprise,”Global Environmental Change 14, no. 3 (2004): 245–58; and the report of the Committee on Abrupt Climate Change—Abrupt Climate Change: Inevitable Surprises (Washington DC: National Academy Press, 2002).

  • 57

    This is a point stressed by Cass Sunstein in Laws of Fear: Beyond the Precautionary Principle (Cambridge: Cambridge University Press, 2005), 26–34.

  • 58

    My invocation of R1 and R2 in support of a precautionary policy is broadly in line with Stephen Gardiner's analysis of the precautionary principle and his application of it to global climate change in Gardiner, “Ethics and Global Climate Change,” 577–78. See also his excellent treatment in “A Core Precautionary Principle,”Journal of Political Philosophy 14, no. 1 (2006): 33–60. Gardiner draws on Rawls's maximin principle to construct what he terms the “Rawlsian Core Precautionary Principle” (p. 48). The latter holds that precaution is appropriate when (i) there is uncertainty; (ii) people do not particularly value increases above the kind of minimum guaranteed by the maximin principle; and (iii) people strongly object to falling below the minimum standard guaranteed by maximin (p. 47). As he says, this interpretation of the precautionary principle entails that we should adopt a precautionary approach to global climate change (p. 55). Gardiner's treatment in “A Core Precautionary Principle” is slightly different to his earlier treatment in “Ethics and Global Climate Change” for whereas the former applies the precautionary principle only to cases of uncertainty, the latter applies it to cases where there is a “high” probability of severe effects and an “unknown” probability of catastrophe (see “Ethics and Global Climate Change,” 577). My account is closer to this second account, though, by contrast with Gardiner's account, the concept of rights plays a crucial role in my argument.

  • 59

    Stern, The Economics of Climate Change, chap. 4, esp. pp. 106–14. See also Parry et al., “Technical Summary,” 64; and Michel Boko, Isabelle Niang, Anthony Nyong, and Coleen Vogel, “Africa,” in Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. Martin Parry, Osvaldo Canziani, Jean Palutikof, Paul van der Linden, and Clair Hanson (Cambridge: Cambridge University Press, 2007), esp. p. 435.

  • 60

    For an excellent discussion see Sven Ove Hansson, “Ethical Criteria of Risk Acceptance,”Erkenntnis 59, no. 3 (2003): 291–309, esp. 305. The example of driving comes from p. 298. I disagree with Hansson's proposal but will not pursue that here.

  • 61

    On this point, I am in full agreement with Henry Shue's analysis in “Deadly Delays, Saving Opportunities: Creating a More Dangerous World?” in Energy and Responsibility, ed. Denis Arnold (forthcoming), 16. Shue relies on something like my D1 and D2, though he does not couch his arguments in terms of human rights. Shue also eschews any appeal to the possibility of catastrophic climate change (that referred to by (b) in my D2) on the grounds that the probability is not high enough (see “Deadly Delays,” 12–13).

  • 62

    I am relying here on the assumption that persons are entitled to emit subsistence emissions. See Henry Shue, “Subsistence Emissions and Luxury Emissions,”Law and Policy 15, no. 1 (1993): 39–59.

  • 63

    Even if one rejects the claim that they can be justified in emitting subsistence emissions in such circumstances, one might hold that their behavior is excusable. For a canonical statement of this distinction see J. L. Austin, “A Plea for Excuses,”Proceedings of the Aristotelian Society 57 (1956–1957): 1–30.