The Parties to the UNFCCC and Paris Agreement agreed to act "on the basis of equity" to protect the climate system. Equitable effort-sharing is an irreducibly normative matter, yet some influential studies have sought to create quantitative indicators of equitable effort that claim to be value-neutral (despite evident biases). Many of these studies fail to clarify the ethical principles underlying their indicators, some mislabel approaches which favour wealthy nations as 'equity approaches', and some combine contradictory indicators into composites we call 'derivative benchmarks'. This Perspective reviews influential climate effort sharing assessments and presents guidelines for developing and adjudicating policyrelevant (but not ethically neutral) equity research.

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Martha Nussbaum has expanded the capabilities approach to defend positive duties of justice to individuals who fall below Rawls' standard for fully cooperating members of society, including sentient nonhuman animals. Building on this, David Schlosberg has defended the extension of capabilities justice not only to individual animals but also to entire species and ecosystems. This is an attractive vision: a happy marriage of social, environmental and ecological justice, which also respects the claims of individual animals. This paper asks whether it is one that the capabilities approach can really deliver. Serious obstacles are highlighted. The potential for conflict between the capability-based entitlements of humans and those of nonhuman animals or 'nature' is noted, but it is argued that this does not constitute a decisive objection to the expanded capabilities approach. However, intra-nature conflicts are so widespread as to do so: the situation is outside the circumstances of justice as they are standardly understood. Schlosberg attempts to reconcile such conflicts by re-examining what it means to flourish as a sentient nonhuman animal. This fails, because of the distinction between flourishing as a species, which often requires predation, and flourishing as an individual, which is as frequently incompatible with it. Finally, the paper considers how a capabilities theorist might move beyond such conflicts, identifying two possible strategies (which are not themselves unproblematic) for reconciling the demands of humans, animals and ecosystems.

Liberalism faces a tension between its commitment to minimal interference with individual liberty and the urgent need for strong collective action on global climate change. This paper attempts to resolve that tension. It does so on the one hand by defending an expanded model of collective moral responsibility, according to which a set of individuals can be responsible, qua "putative group", for harm resulting from the predictable aggregation of their individual acts. On the other, it defends a collectivised version of the harm principle. The claim is that the collectivised harm principle pushes the burden of argument, against coercively enforced measures to curtail climate change and compensate its victims, onto the global elite collectively responsible for environmental harms. Some such potential arguments are briefly considered and rejected. Main text There is an urgent need to tackle global climate change. This is hard for liberals, or anyone else, to deny. However, there is a serious obstacle to doing so within the framework of liberalism-a school of thought centred, as Feinberg (1987, p. 14) has put it, on keeping liberty-limiting principles to a minimum. Any serious collective

However far we are from either in practice, basic global and intergenerational justice, including climate change mitigation, are taken to be theoretically compatible. If population grows as predicted, this could cease to be the case. This paper asks whether that tragic legacy can now be averted without hard or even tragic choices on population policy. Current generations must navigate between: a high-stakes gamble on undeveloped technology; violating human rights; demanding unbearable sacrifices of the already badly off; institutional unfairness across adults; institutional unfairness across children; failing to protect children’s basic interests; and threatening the autonomy of the family. We are not yet forced to choose between bequeathing a tragic choice and making one, by adopting basically unjust measures. However, even the remaining options present a morally hard choice. The fact we face it is yet another damning indictment on the combined actions and collective failures of the global elite.