1. Compare Risse’s and Nine’s approach to the issue of climate refugees.
Which is superior and why?
2. What is the appropriate discount rate to use when determining what steps
should be taken to address human-caused global warming?
3. What role, if any, should de-extinction play as a response to climate






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Climate Change and the Future: Discounting for Time,
Wealth, and Risk
Simon Caney
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
JOURNAL of SOCIAL PHILOSOPHY, Vol. 40 No. 2, Summer 2009, 163–186.
© 2009 Wiley Periodicals, Inc.
Simon Caney
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
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
Climate Change and the Future
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
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
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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
Climate Change and the Future
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
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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 containerperson.”24 Given the problems with this argument, let us consider an alternative
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
Climate Change and the Future
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
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 …
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