Prioritizing the welfare of vulnerable nations promotes equitable achievement of Paris target

Abstract Equitable mitigation to limit warming to 2°C has been central to international climate negotiations and global action. Approximately half of the mitigation pathways in the Intergovernmental Panel on Climate Change report use Cost-benefit Integrated Assessment Models (CB-IAMs). These pathways are sensitive to normative assumptions ingrained in CB-IAMs and have been criticized for unfairly burdening developing nations. Here, we show that making normative assumptions explicit, separating conflicting policy objectives, and employing adaptive policies can substantially alter the prescribed global mitigation pathways and the underlying mitigation responsibility. Our findings show that ethical framing is pivotal. A utilitarian framing (maximizing global welfare) results in less ambitious mitigation, exceeding 2°C warming and unjustly distributing responsibilities. In contrast, a prioritarian framing (prioritizing the worst-off) prescribes pathways meeting Paris Agreement goals and ensuring equitable distribution of mitigation responsibility. Our approach integrates diverse ethical perspectives, facilitating informed deliberation and enabling stakeholders to achieve a negotiated compromise.