Navigating the black box of fair national emissions targets

Current national emissions targets fall short of the Paris Agreement goals, prompting the need for equitable ways to close this gap. Fair emissions allowances rely on effort-sharing formulas based on fairness principles, yielding diverse outcomes. These variations, shaped by normative decisions, complicate policymaking and legal assessments of climate targets. Here we provide up-to-date numbers, comprehensively accounting for three dimensions—physical and social uncertainties, global strategies and equity—and the relative impact of them on each country’s emissions allowance. In the short run, normative considerations substantially impact fair emissions allowances—directing current discussions to this debate—while global discussions on temperature targets and non-CO2 emissions take over in the long run. We identify many countries with insufficient nationally determined contributions in light of fairness and discuss implications for increased domestic mitigation and financing emissions reductions abroad—yielding a total international finance flux of $US0.5–7.4 trillion in 2030.