Despite the scientific consensus that fossil fuel production requires drastic curtailment to avoid exceeding 1.5 °C above pre-industrial levels, the supply-side question of which countries should start phasing out which fuels, and in what sequence, remains without a rigorous and comprehensive methodology addressing, capacity, responsibility concerns, and ecological impact altogether. This paper introduces the PACER index (Phaseout Allocation based on Capacity and Equitable Responsibility), a multi-criteria composite index for oil and natural gas that operationalises the principle of common but differentiated responsibilities on the production side. Like a mass-participation marathon in which runners with different personal capabilities set off in successive waves at different times, with pacers that help each people meet their time targets, PACER assigns countries to phase-out waves based on their capacity and responsibility, ensuring that the global decarbonisation finish line is reached on schedule while the burden is fairly distributed.
The index integrates six evidence-based criteria across three equally-weighted dimensions: (i) Ecological Cost, comprising the carbon intensity of extraction; (ii) Environmental Justice, comprising historical cumulative emissions and annual GHG emissions per capita; and (iii) Economic ease, comprising national income, fossil fuel export dependence, and non-oil-gas GDP per capita. Several results emerge. the United States, Canada, Australia, Trinidad and Tobago, and the United Kingdom carry the greatest oil phase-out responsibility and together account for 25.2% of global oil production. Two 1.5°C-consistent scenarios are modelled: a Time Equity Scenario (requiring the same 67.6% reduction in oil and 45% reduction in gas production by 2050, with Wave 1 countries acting by 2035); and a Volumetric Equity Scenario, in which all waves share the same 2050 deadline but face differentiated reduction percentages. Interestingly, for gas, the reductions for wave 1 and wave 2 countries suffice to meet a 1.5°C scenario, with the rest of nations requiring no mandatory reduction. An interactive online tool allows users to adjust pillar weights and explore the sensitivity of rankings in real time.