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. 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. Prof. Simon have argued elsewhere that it jeopardizes fundamental human rights. 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. The 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. 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. 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.