Applying Satellite Observations to Improve Bottom-Up National Emission Inventories for Methane: Application to Colombia

Abstract. Countries report bottom-up inventories of methane emissions under the Paris Agreement to the United Nations Framework Convention on Climate Change (UNFCCC), but these inventories can have large uncertainties in activity data and emission factors. Top-down information from inversion of satellite observations can provide valuable constraints to improve these estimates, but has been limited by coarse resolution and the use of inadequate emission inventories as prior estimates. Here, we combine inventory and atmospheric data to quantify 2023 national emissions in Colombia. We use satellite observations from TROPOMI, GOSAT, and point source imagers (GHGSat, EMIT, aircraft AVIRIS-NG) in an analytical inversion at ≈12×12 km² resolution with the Integrated Methane Inversion v2.0 framework. We construct a spatially-resolved version of the national bottom-up emission inventory from the Biennial Update Report (BUR) to the UNFCCC for use as prior estimate in the inversion, and combine it with high-resolution wetland extent data (GLWDv2) to separate anthropogenic from wetland emissions. Total posterior methane emissions are 8.9 (8.7–9.1) Tg a^-1 contributed by wetlands (5.7 (5.5–6.0) Tg a^-1) and anthropogenic emissions (3.2 (3.1–3.2) Tg a^-1), mainly livestock (2.0 (1.9–2.1) Tg a^-1) and waste (0.76 (0.74–0.76) Tg a^-1). Adjustments relative to the BUR are +18 % for livestock, +19 % for waste, +60 % for oil/gas, and +92 % for coal. We provide recommendations to improve the BUR, offering a blueprint for combining satellite observations with national inventory data to produce sectorally and spatially resolved emissions estimates that can inform mitigation planning.