Reconciliation of updated greenhouse gas budgets from UNFCCC national inventories and atmospheric inversions

<p>Assessing and understanding the causes of mismatches between inversion results and inventories is key to future greenhouse gas budget estimates and also a contribution to phase 2 of the REgional Carbon Cycle Assessment and Processes (RECCAP2) initiative. Here, we compare the latest greenhouse gas budgets from the updated National Greenhouse Gas Inventories (NGHGIs) submitted to the United Nations Framework Convention on Climate Change (UNFCCC) and from the updated atmospheric inversions based on both in-situ and satellite observations. We compile the latest global harmonized NGHGI database for all countries according to the updated national communications (NCs) and biennial update reports (BURs) by the end of the year 2022. With the updated global atmospheric inversion results of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) produced by the Global Carbon Project, we adjust the inversion results of all countries for comparison, considering lateral river transfer processes and trade in crop and timber products, as well as the role of carbon sequestration in unmanaged land not considered by NGHGI, and compare them with greenhouse gas budgets in national inventories. The results show that there is a good consistency in net land CO₂ flux based on the global in-situ network and that using satellite CO₂ retrievals over tropical countries like Congo, Brazil, Peru, South Africa, and so on. For CH₄, while the uncertainties of inversion results have been reduced in the updated global inversion ensembles compared to the previous ones, it seems that oil and gas-extracting countries like Saudi Arabia and Qatar report lower emissions compared to those estimated by inversions. This study is a reapplication of the methodologies developed by our previous study, which are confirmed and could be applied regularly and show how inversion could be used systematically in the future to support the assessment and improve the inventory of the Paris Agreement.</p>