Impact of population growth and population ethics on climate change mitigation policy

Future population growth is uncertain and matters for climate policy: higher growth entails more emissions and means more people will be vulnerable to climate-related impacts. We show that how future population is valued importantly determines mitigation decisions. Using the Dynamic Integrated Climate-Economy model, we explore two approaches to valuing population: a discounted version of total utilitarianism (TU), which considers total wellbeing and is standard in social cost of carbon dioxide (SCC) models, and of average utilitarianism (AU), which ignores population size and sums only each time period’s discounted average wellbeing. Under both approaches, as population increases the SCC increases, but optimal peak temperature decreases. The effect is larger under TU, because it responds to the fact that a larger population means climate change hurts more people: for example, in 2025, assuming the United Nations (UN)-high rather than UN-low population scenario entails an increase in the SCC of 85% under TU vs. 5% under AU. The difference in the SCC between the two population scenarios under TU is comparable to commonly debated decisions regarding time discounting. Additionally, we estimate the avoided mitigation costs implied by plausible reductions in population growth, finding that large near-term savings ($billions annually) occur under TU; savings under AU emerge in the more distant future. These savings are larger than spending shortfalls for human development policies that may lower fertility. Finally, we show that whether lowering population growth entails overall improvements in wellbeing—rather than merely cost savings—again depends on the ethical approach to valuing population

Broad cross-national public support for accelerated COVID-19 vaccine trial designs.

A vaccine for COVID-19 is urgently needed. Several vaccine trial designs may significantly accelerate vaccine testing and approval, but also increase risks to human subjects. Concerns about whether the public would see such designs as ethical represent an important roadblock to their implementation; accordingly, both the World Health Organization and numerous scholars have called for consulting the public regarding them. We answered these calls by conducting a cross-national survey (n = 5920) in Australia, Canada, Hong Kong, New Zealand, South Africa, Singapore, the United Kingdom, and the United States. The survey explained key differences between traditional vaccine trials and two accelerated designs: a challenge trial or a trial integrating a Phase II safety and immunogenicity trial into a larger Phase III efficacy trial. Respondents' answers to comprehension questions indicate that they largely understood the key differences and ethical trade-offs between the designs from our descriptions. We asked respondents whether they would prefer scientists to conduct traditional trials or one of these two accelerated designs. We found broad majorities prefer for scientists to conduct challenge trials (75%) and integrated trials (63%) over standard trials. Even as respondents acknowledged the risks, they perceived both accelerated trials as similarly ethical to standard trial designs. This high support is consistent across every geography and demographic subgroup we examined, including vulnerable populations. These findings may help assuage some of the concerns surrounding accelerated designs

Human Health and the Social Cost of Carbon: A Primer and Call to Action.

The health co-benefits of CO2 mitigation can provide a strong incentive for climate policy through reductions in air pollutant emissions that occur when targeting shared sources. However, reducing air pollutant emissions may also have an important co-harm, as the aerosols they form produce net cooling overall. Nevertheless, aerosol impacts have not been fully incorporated into cost-benefit modeling that estimates how much the world should optimally mitigate. Here we find that when both co-benefits and co-harms are taken fully into account, optimal climate policy results in immediate net benefits globally, overturning previous findings from cost-benefit models that omit these effects. The global health benefits from climate policy could reach trillions of dollars annually, but will importantly depend on the air quality policies that nations adopt independently of climate change. Depending on how society values better health, economically optimal levels of mitigation may be consistent with a target of 2?°C or lower

What Should We Agree on about the Repugnant Conclusion?

The Repugnant Conclusion served an important purpose in catalyzing and inspiring the pioneering stage of population ethics research. We believe, however, that the Repugnant Conclusion now receives too much focus. Avoiding the Repugnant Conclusion should no longer be the central goal driving population ethics research, despite its importance to the fundamental accomplishments of the existing literature

Collective Action, Climate Change, and the Ethical Significance of Futility

Some collective action problems are easy. For example, if a tragedy of the commons arises within a nation's borders, and if it is clear that the problem can be solved only by a particular kind of coercive governmental response, and if it is clear that every citizen would want the government to adopt such a response, then the government should adopt such a response, and such a response is justified. This is an easy collective action problem because it is obvious what course of action should be taken, and it is also clear enough why that course of action would be justified. In this dissertation I answer questions that arise from the most difficult collective action problems, such as our situation with respect to climate change, with respect to which neither economists nor philosophers have made any real progress. For example, in the first chapter I answer the following question: What should we do when we face a collective action problem that is impervious to our standard tools for achieving cooperation and avoiding a tragic outcome? In other words, what should we do when we are unable to rely on benevolent human dispositions, natural `market-based' coordination, bargaining, governmental coercion, and other familiar mechanisms to avoid an undesirable outcome? My answer is that even when our standard tools are useless, we can often escape a tragic dilemma by turning the force of such a dilemma against itself. The trick is to intentionally place ourselves into a new dilemma of our own design, the predictable outcome of which is a desirable solution to the initial, otherwise insoluble dilemma. For example, with respect to anthropogenic climate change, where any effective response will be contrary to the interests of the current citizens of many nations, the trick is to engineer and introduce an international climate treaty that creates something like a multi-player prisoner's dilemma at the level of nations, the predictable outcome of which is that all nations will agree to the treaty, thereby making the current citizens of some of those nations worse off relative to the no-treaty status quo as a side-effect of a mechanism within the treaty that effectively combats climate change. I show that such a treaty is the only attractive option if - as seems true - we must secure the cooperation of many influential nations whose current citizens will be made worse off by any effective response, and if such nations are disposed to reject or pull out of treaties whenever they are contrary to the interests of their current citizens. I also explain why such a treaty is the key to engineering the most ethical climate treaty possible, and to making genuine progress beyond the unpromising incrementalist, idealist, and hard-headed realist approaches to climate treaties that dominate the literature in philosophy, politics, economics, and law. More generally, the result is a straightforward, realistic, and non-coercive framework for constructing economically and ethically optimal solutions to many previously intractable collective action problems. In a later chapter I show that nations can be justified in acting in ways that make their citizens worse off, are unfair to their citizens, and that would be reasonably rejected by their citizens - which provides a counterexample to many political theories. Such situations arise most clearly when the citizens of a nation are, through no fault of their own, morally required to favor a national course of action that is unfair to them, contrary to their interests, and contrary to the interests of future generations of their descendants and fellow citizens. Arguably, the United States is in such a situation with respect to climate change, given that inaction on the part of the US may well ensure a catastrophic outcome for untold billions of future people, and given that any real solution to the problem arguably requires the US to agree to a climate treaty that is unfair to its citizens and contrary to their interests. At the same time, even given the gravest worst-case-scenario assumptions about the effects of climate change, I argue that individual citizens are not required to reduce their emissions by a significant amount, because without an effective global response such reductions are both costly and futile in a way that makes such reductions not required. In fact, I argue that such futility and lack of requirement at the individual level explains why individuals are required to favor a coercive intergovernmental response to climate change, and why nations are justified in adopting such a response even if it is unfair to their citizens and contrary to their interests. (Here it might be useful to recall that in the first chapter I explain why an effective intergovernmental solution is realistic even given pessimistic assumptions about the collective action problem that arises at the level of nations.) In the course of arguing for these conclusions, I make progress on a number of issues at the foundations of normative ethics and political philosophy. Among other things, I identify the subtle contours of the ethical significance of futility, which has not been adequately investigated by philosophers and other theorists, and is of great practical and theoretical importance, because worries about the futility of individual action arise in almost every area of practical concern, and threaten to undermine most normative theories. In the course of my discussion, I show that existent normative theories are unable to offer a plausible account of what individuals are required to do in the kind of collective action situations that are commonplace in a market-based society, and are therefore unable to explain many of the most important facts about modern moral life. In particular, results from economics and political science that have been unappreciated by philosophers help to clarify that for straightforward mathematical and empirical reasons an appeal to expected consequences cannot possibly deliver the verdicts on such cases that consequentialists themselves assume. In addition, alternative theories that appeal to `universalizability', `direct harm', and other notions also cannot deliver plausible verdicts on such cases. For these and other reasons, I argue that a plausible account of what individuals are required to do in a large market-based society must invoke a distinction between activities that are essential to a product or to the actual production of a product, and activities that are not. These and other results related to futility have important practical implications, because many serious practical issues are tied to situations in which the action of individuals is in some sense futile - for example, whether individuals are required to contribute to charities that help innocent people who are suffering from easily curable afflictions, whether it is permissible to consume animal products given the terrible way that many animals are treated, whether it is permissible to consume products that are produced in a way that harms or exploits other people, and, of course, whether individuals are required to reduce their greenhouse gas emissions. In the last two chapters I show that morality and other forms of normativity are sometimes dramatically directly collectively self-defeating, where a normative system has that property when it requires everyone to act in a way that everyone can see is certain to be dramatically worse along the relevant normative dimension than if everyone did not follow the requirements of that normative system instead. This shows that a wide range of normative theories are either false, or at least don't have the consequences that their adherents take them to have, including consequentialist theories, contractualist theories, Kantian theories, universalization theories, enlightened self-interest theories, and many other normative theories. It also means that morality and other forms of normativity cannot be relied upon to solve collective action problems even in a world of normatively flawless agents. One practical upshot is that even when a disaster will ensue if everyone acts in a particular way or on a particular principle, that doesn't settle the question of whether individuals are permitted to act in that way or on that principle. In sum, I provide answers to the most pressing questions about what we should do about difficult collective action problems, especially when non-cooperation would lead to catastrophe

Utilitarian benchmarks for emissions and pledges promote equity, climate and development.

Tools are needed to benchmark carbon emissions and pledges against criteria of equity and fairness. However, standard economic approaches, which use a transparent optimization framework, ignore equity. Models that do include equity benchmarks exist, but often use opaque methodologies. Here we propose a utilitarian benchmark computed in a transparent optimization framework, which could usefully inform the equity benchmark debate. Implementing the utilitarian benchmark, which we see as ethically minimal and conceptually parsimonious, in two leading climate-economy models allows for calculation of the optimal allocation of future emissions. We compare this optimum with historical emissions and initial nationally determined contributions. Compared with cost minimization, utilitarian optimization features better outcomes for human development, equity and the climate. Peak temperature is lower under utilitarianism because it reduces the human development cost of global mitigation. Utilitarianism therefore is a promising inclusion to a set of benchmarks for future explorations of climate equity

The Social Cost of Carbon: Valuing Inequality, Risk, and Population for Climate Policy

International audienceWe analyze the role of ethical values in the determination of the social cost of carbon, arguing that the familiar debate about discounting is too narrow. Other ethical issues are equally important to computing the social cost of carbon, and we highlight inequality, risk, and population ethics. Although the usual approach, in the economics of cost-benefit analysis for climate policy, is confined to a utilitarian axiology, the methodology of the social cost of carbon is rather flexible and can be expanded to a broader set of social-welfare approaches

Broad cross-national public support for accelerated COVID-19 vaccine trial designs.

A vaccine for COVID-19 is urgently needed. Several vaccine trial designs may significantly accelerate vaccine testing and approval, but also increase risks to human subjects. Concerns about whether the public would see such designs as ethical represent an important roadblock to their implementation; accordingly, both the World Health Organization and numerous scholars have called for consulting the public regarding them. We answered these calls by conducting a cross-national survey (n = 5920) in Australia, Canada, Hong Kong, New Zealand, South Africa, Singapore, the United Kingdom, and the United States. The survey explained key differences between traditional vaccine trials and two accelerated designs: a challenge trial or a trial integrating a Phase II safety and immunogenicity trial into a larger Phase III efficacy trial. Respondents' answers to comprehension questions indicate that they largely understood the key differences and ethical trade-offs between the designs from our descriptions. We asked respondents whether they would prefer scientists to conduct traditional trials or one of these two accelerated designs. We found broad majorities prefer for scientists to conduct challenge trials (75%) and integrated trials (63%) over standard trials. Even as respondents acknowledged the risks, they perceived both accelerated trials as similarly ethical to standard trial designs. This high support is consistent across every geography and demographic subgroup we examined, including vulnerable populations. These findings may help assuage some of the concerns surrounding accelerated designs