A justice-based framework to determine countries’ fair warming contributions to Paris Agreement

Abstract Equity is a cornerstone of global climate policy, yet no international agreement has managed to agree on how to allocate mitigation efforts across countries. While a rich literature informs these deliberations, there remains a gap in approaches that appropriately consider non-CO2 emissions and their warming contributions. In this study, we define a global warming budget applicable to all anthropogenic greenhouse gases and allocate it to countries based on equity principles drawn from international environmental law. We find that by 2021 up to 85 countries, including all major developed countries, exhausted their budget compatible with keeping warming to 1.5°C under all allocation approaches considered in this study. A similar picture emerges for 2°C. A large group of countries will hence exceed their fair shares even if their updated pledges under the Paris Agreement represent the deepest possible reductions. Considerations of fairness should therefore start to include aspects beyond domestic emissions reductions only.