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

Abstract

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 have as to current generations resources to contemporaries than to future or the case for combating climate change. In this I different of for I that of these is My in case to the of human It that a human to climate change us to of these To the question of how current generations should make which on the interests of future it is to the of a social discount by from and to contemporary It to the rate by which the of future generations to resources by current generations or or remains A social discount the to which resources should be to interests in to interests at a The the positive social discount rate the should be spent on the To the and it to the of climate it is to have some in of The argued that the of a level of climate to approximately one of global in this of to a of by the question to be is whether this is spent on current generations or on future one that the should be spent on current generations than future of the social discount rate of which be with in there is time that it is to a lower to human interests the they are in the future of the that they in the one for a social discount rate is that one it to time more have argued that time is that time a for and the of by it is human a that time at which a the of from a of and that the interests of a as much as of time however, is from the we to the of intergenerational equity. Suppose that one that there should not be time to devote resources to current people future people for a depending on of intergenerational equity one to this is to intergenerational to one for a a of that to a current It will have it to whether have or whether some have than the intergenerational to time are the of we have this we have to it be or a difference or or a or a or the question at the intergenerational the of time we to whether generations should be by a of or the or whatever the or The is that one that current generations should devote resources to current generations in to future generations of the one and The so do not the one devote resources to current generations future to do so from of of future we of the impacts of climate change. we that human life will continue to the on The of Climate Change by to the that for it to the sea and temperature and how likely It also of some for one for climate change on human no for one is not that there will be on human life so it be there is a case for the which one is to on a from it is the on the one and on the to one and can the that it will on the other to one is not to the of its to us for they are one to one can the and makes on that we this of is to this we that the to which people devote resources to the present as to the future is a of the the of time we to their the of intergenerational of the people the of the these and the of human we that we are will in to human us one in the social discount rate and one for current generations future generations that on this one The to be makes the generations should current generations the interests of future generations it is even for current people to engage in time a positive time discount we it that current generations should on mitigation and adaptation than they a time discount In I this and I the to be it is to the apply a time discount rate to As and have argued for the of this A a positive time discount What have in is their that one should in the should be to the or time discount A however, be a more the a time discount rate to some not to more the it that there is a of different it I the that have human to the of fundamental human interests from the by climate change. Climate change jeopardizes human for the to life and freak weather and will to human the to the increase in and sea will to and the to climate change will to to and and the to and freak weather events and and the not to be to will of or to The for the and the of these of which are by climate There are a number of different of these I that they are on the that they human interests that are to on the of the to be that a time discount rate should be applied to the it not be applied to other or that are by climate change should thus be no in other more interests to to more the in be to a positive time discount generations should so as not to a of in which people in one hundred time are to their be to future interests in than current in that of the is not to for a positive time discount rate for other as It simply the that that be the My is more on the not discount current and future and the to from climate change is in the I have the not the to time that it I to some for the that the by climate change should not be to a positive time discount rate and us a time discount The most is one by and by In The of a of in future future or should us with the as they for their The the of in be so that time should have no is that the of requires not according to a of it is in To prefer a of at to a of at to a level of the in The of It is on the of this that that time is a of in is this will not a of the even we this the of this are It a and for very to the of and its to I think that that is the and a deep in the situation of is in the The a with than they be by a positive time discount that that is not by a to the and the of future people it so is with the of and it that a time discount rate that It well that as the with this us A to a to the of and to the the The of that should not or people on the of that fundamental It is on this that we that should not be of their or or do not to of In the however, it to a simply of their in for that It be to some in some they are more or more or they some other simply the future is not one of these the other in time is not the of to To this we of a time discount rate for this the of by the to is of fundamental from a of and the time discount rate from that that is the of it that time at which a the of from a of and that the interests of a as much as of can be applied to the the the fundamental of the The for the of of case The to this that is to on makes no to that is the of fundamental interests and the of the on that how whether it is and so is not a The of the case for that there should be a time discount rate for the of a of by the of and for their interests in it no for of these for some than for thus the of time discount rate to the of that the not us to a time discount rate to other It simply to the and that these do not time As it of on of time discount rate is for other In this the in this It be at this to take and to to the case of climate change. 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