National greenhouse gas budgets reconciliation 2025

In this study, we provide an update on the methodology and data to compare the national greenhouse gas inventories (NGHGIs) and atmospheric inversion model ensembles contributed by international research teams coordinated by the Global Carbon Project. The comparison framework uses transparent processing of the net ecosystem exchange fluxes of carbon dioxide (CO₂) from inversions to provide estimates of terrestrial carbon stock changes over managed land that can be used to evaluate NGHGIs. For methane (CH₄), and nitrous oxide (N₂O), we separate anthropogenic emissions from natural sources based directly on the inversion results to make them compatible with NGHGIs. Our global harmonized NGHGI database was updated with inventory data by compiling data from the first biennial transparency reports (BTRs) under the Paris Agreement, providing the first annual time-series official reported values in most non-Annex I countries. For the inversion data, we used an ensemble of 30 global inversions produced for the most recent assessments of the global CO₂ and CH₄ budgets coordinated by the Global Carbon Project with ancillary data, and 6 inversion results of CH₄ budgets from Ciais et al, 2026. The inversion ensemble in this study goes through 2024, building on our previous report from 1990 to 2021. The methodology proposed here to compare inversion results with NGHGIs can be applied regularly for monitoring the effectiveness of mitigation policy and progress by countries to meet the objectives of their pledges.