Comparing national greenhouse gas budgets reported in UNFCCC inventories against atmospheric inversions
- 1Department of Earth System Science, Tsinghua University, Beijing, China
- 2Laboratoire des Sciences du Climat et de l’Environnement/ IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
- 3Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing, China
- 4Earth System Risk Analysis Section, Earth System Division, National Institute for Environmental Studies (NIES), Tsukuba, Japan
- 5NILU - Norsk Institutt for Luftforskning, Kjeller, Norway
- 6International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA
- 7CSIRO Oceans and Atmosphere, Aspendale 3195, Australia
- 8UMR-ECOSYS, Université Paris-Saclay, INRAE, AgroParisTech, Thiverval-Grignon, France
- 9Department of Atmospheric Sciences, University of Illinois, Urbana, IL 61801, USA
- 10Max Planck Institute for Biogeochemistry, Dept. of Biogeochemical Integration, Hans Knöll Str. 10, 07745 Jena, Germany
- 11College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK
- 12National Centre for Earth Observation, University of Edinburgh, Edinburgh EH9 3FF, UK
- 13School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FF, UK
- 14Kayrros, Paris, France
- 15NASA GSFC, Biospheric Sciences Lab., Greenbelt, MD 20771
- 16College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
- 17Department of Earth and Life Sciences, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- 18Department of Earth System Science, University of California, Irvine
- 19European Commission, Joint Research Centre, Ispra (VA) Italy
- 20European Space Agency Climate Office, ECSAT, Harwell Campus, Oxfordshire, Didcot OX11 0FD, UK
- These authors contributed equally to this work.
Abstract. In support of the Global Stocktake of the Paris Agreement on Climate change, this study presents a comprehensive framework to process the results of atmospheric inversions in order to make them suitable for evaluating UNFCCC national inventories of land-use carbon dioxide (CO2) emissions and removals, corresponding to the Land Use, Land Use Change and Forestry and waste sectors. We also deduced anthropogenic methane (CH4) emissions regrouped into fossil and agriculture and waste emissions, and anthropogenic nitrous oxide (N2O) emissions from inversions. To compare inversions with national reports, we compiled a new global harmonized database of national emissions and removals from periodical UNFCCC inventories by Annex I countries, and from sporadic and less detailed emissions reports by Non-Annex I countries, given by National Communications and Biennial Update Reports. The method to reconcile inversions with inventories is applied to selected large countries covering 78 % of the global land carbon uptake for CO2, as well as emissions and removals in the land use, land use change and forestry sector, and top-emitters of CH4 and N2O. Our method uses results from an ensemble of global inversions produced by the Global Carbon Project for the three greenhouse gases, with ancillary data. We examine the role of CO2 fluxes caused by lateral transfer processes from rivers and from trade in crop and wood products, and the role of carbon uptake in unmanaged lands, both not accounted for by the rules of inventories. Here we show that, despite a large spread across the inversions, the median of available inversion models points to a larger terrestrial carbon sink than inventories over temperate countries or groups of countries of the Northern Hemisphere like Russia, Canada and the European Union. For CH4, we find good consistency between the inversions assimilating only data from the global in-situ network and those using satellite CH4 retrievals, and a tendency for inversions to diagnose higher CH4 emissions estimates than reported by inventories. In particular, oil and gas extracting countries in Central Asia and the Persian Gulf region tend to systematically report lower emissions compared to those estimated by inversions. For N2O, inversions tend to produce higher anthropogenic emissions than inventories for tropical countries, even when attempting to consider only managed land emissions. In the inventories of many non-Annex I countries, this can be tentatively attributed to either a lack of reporting indirect N2O emissions from atmospheric deposition and from leaching to rivers, or to the existence of natural sources intertwined with managed lands, or to an under-estimation of N2O emission factors for direct agricultural soil emissions. The advantage of inversions is that they provide insights on seasonal and interannual greenhouse gas fluxes anomalies, e.g. during extreme events such as drought or abnormal fire episodes, whereas inventory methods are established to estimate trends and multi-annual changes. As a much denser sampling of atmospheric CO2 and CH4 concentrations by different satellites coordinated into a global constellation is expected in the coming years, the methodology proposed here to compare inversion results with inventory reports could be applied regularly for monitoring the effectiveness of mitigation policy and progress by countries to meet the objective of their pledges.
Zhu Deng et al.
Zhu Deng et al.
GHG data from inverse models and UNFCCC national inventories https://doi.org/10.5281/zenodo.5089799
Zhu Deng et al.
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