Satellite-Based Measures for Tracking Atmospheric CO₂ and CH₄ at National, Subnational, and Urban Scales

A scalable method for estimating changes in local greenhouse gas emissions from satellite-based atmospheric composition measures is developed and applied in this paper. The analysis employs large panels of spatially-referenced, time-stamped atmospheric carbon dioxide observations from the National Aeronautics and Space Administration’s Orbiting Carbon Observatory-2 and methane observations from the European Space Agency’s Sentinel-5P. The analysis computes monthly mean concentration anomalies, defined as deviations from global trends. Long- and short-term trend regressions were estimated for cells of high-resolution global grids, and cell-specific results meeting the classical significance test (p ≤ 0.05) were identified as positive or negative trends. These high-resolution findings were aggregated to generate performance scores for geographic areas of arbitrary scale. The global scalability of the approach was demonstrated with performance assessments for 242 countries and disputed areas, 3,242 provinces, 36,563 sub-provinces, 6,672 Functional Urban Areas, and 670 offshore oil and gas production zones. Regional illustrations were provided for 11 Southeast Asian countries, alongside a global overview organized by World Bank regions and income groups. Findings indicated that long-term carbon dioxide decreases outnumbered increases, but recent changes (2024–25) revealed a reversal. By contrast, methane displayed large net decreases in both long- and short-term measures. The results highlighted substantial variation across regions and income groups. Low-income countries showed the strongest movement toward reductions, yet their contributions remain overshadowed by high-income economies, where performance has been mixed. It is hoped that this methodology will inform global policy dialogue by enabling transparent and comparable emissions assessments. The approach also provides a practical tool for identifying emissions hotspots, supporting policy makers at the national and subnational levels in developing targeted mitigation strategies aligned with global climate objectives.