Subnational Methane Emissions Reduction in the U.S. and China: A Bottom-up Evaluation

Methane is a potent greenhouse gas that significantly contributes to global warming, yet most studies to date have focused on national-level methane assessments or on carbon dioxide instead. Our study provides one of the first rigorous, systematic, bottom-up evaluations of methane mitigation at the subnational level for two of the world’s largest emitters, the United States and China. We compile 250 policies across U.S. states and Chinese provinces (1990–2022) and evaluate them using an eight-element rubric of comprehensiveness and ambition. By comparing state- and provincial-level policies, we reveal critical implementation gaps as well as opportunities for scaling mitigation strategies. Utilizing a comprehensive dataset and a novel three-dimensional analytical framework, we assess policy comprehensiveness, ambition, and effectiveness. Our findings underscore the potential for subnational policies to accelerate near-term climate mitigation efforts. This study offers actionable insights for policymakers, suggesting that comprehensive, enforceable, cross-sector frameworks–combined with transparent and accurate data–are consistently associated with stronger methane reductions.