Quantifying animal wellbeing and estimating optimal tradeoffs against human wellbeing, developing policy-relevant population ethics, and integrating the results into policy analysis for climate change and beyond.

Abstract: Animal welfare is almost never incorporated into large-scale policy analyses and investment analyses, even though it is common to quantify the consequences for human welfare in these decision analyses. This is partly due to prejudice, but increasingly also because we do not currently have good methods for quantifying animal wellbeing consequences and putting them on the same scale as quantified human wellbeing consequences. We might call this ‘the problem of interspecies comparisons’. We develop methods to overcome this problem and integrate animal welfare into policy and investment analysis, and provide a worked example via the widely-used optimal climate policy model DICE. In addition, we begin to explore general implications of integrating population ethics into policy analysis, as well as more philosophical questions about axiology. This leads to a number of observations: in contrast to suggestions by John Broome and others, population ethics might not make much of a difference for climate and other policy challenges. This is partly because various feasibility constraints and empirical facts such as global income growth appear to create situations in which the range of leading axiologies converge on the same ‘corner solution’ within the feasible set of policy options. At the very least, we suggest that population ethics is no different in kind and in modeling practice than other familiar empirical and normative uncertainties – e.g. about climate sensitivity, or the relationship between income and wellbeing – and can be readily integrated into models via parameterizations. From a more philosophical perspective, we note that totalism satisfies bounded versions of all the desiderata that impossibility theorems show cannot all be satisfied in unbounded versions – and we find it unmotivated to insist that the repugnant conclusion must be avoided in the first place, since it turns out to be an implication of any plausible welfarist axiology. We believe this provides reason to be comfortable with the totalist axiology assumed by many intergenerational policy analysis models, such as DICE and other climate policy models. (Based on co-authored papers with Dean Spears.)