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- Title
Comparing national greenhouse gas budgets reported in UNFCCC inventories against atmospheric inversions.
- Authors
Deng, Zhu; Ciais, Philippe; Tzompa-Sosa, Zitely A.; Saunois, Marielle; Qiu, Chunjing; Tan, Chang; Sun, Taochun; Ke, Piyu; Cui, Yanan; Tanaka, Katsumasa; Lin, Xin; Thompson, Rona L.; Tian, Hanqin; Yao, Yuanzhi; Huang, Yuanyuan; Lauerwald, Ronny; Jain, Atul K.; Xu, Xiaoming; Bastos, Ana; Sitch, Stephen
- 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 an ensemble of atmospheric inversions in order to make their net ecosystem exchange (NEE) carbon dioxide (CO 2) flux suitable for evaluating national greenhouse gas inventories (NGHGIs) submitted by countries to the United Nations Framework Convention on Climate Change (UNFCCC). From inversions we also deduced anthropogenic methane (CH 4) emissions regrouped into fossil and agriculture and waste emissions, as well as anthropogenic nitrous oxide (N 2 O) emissions. To compare inversion results with national reports, we compiled a new global harmonized database of 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. No gap filling was applied. The method to reconcile inversions with inventories is applied to selected large countries covering ∼90 % of the global land carbon uptake for CO 2 and top emitters of CH 4 and N 2 O. 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 CO 2 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 NGHGIs. 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 CH 4 , we find good consistency between the inversions assimilating only data from the global in situ network and those using satellite CH 4 retrievals and a tendency for inversions to diagnose higher CH 4 emission estimates than reported by NGHGIs. 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 N 2 O, 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 a lack of reporting indirect N 2 O emissions from atmospheric deposition and from leaching to rivers, to the existence of natural sources intertwined with managed lands, or to an underestimation of N 2 O emission factors for direct agricultural soil emissions. Inversions provide insights into 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 CO 2 and CH 4 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 (e.g., NGHGIs) could be applied regularly for monitoring the effectiveness of mitigation policy and progress by countries to meet the objective of their pledges. The dataset constructed by this study is publicly available at 10.5281/zenodo.5089799 (Deng et al., 2021).
- Subjects
GREENHOUSE gases; ATMOSPHERIC carbon dioxide; INVENTORIES; PARIS Agreement (2016); CARBON cycle; ATMOSPHERIC deposition; INVERSION (Geophysics); SOIL sampling
- Publication
Earth System Science Data, 2022, Vol 14, Issue 4, p1639
- ISSN
1866-3508
- Publication type
Article
- DOI
10.5194/essd-14-1639-2022