A Caltech Library Service

Global atmospheric CO₂ inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate

Gaubert, Benjamin and Stephens, Britton B. and Basu, Sourish and Chevallier, Frédéric and Deng, Feng and Kort, Eric A. and Patra, Prabir K. and Peters, Wouter and Rödenbeck, Christian and Saeki, Tazu and Schimel, David and Van der Laan-Luijkx, Ingrid and Wofsy, Steven and Yin, Yi (2019) Global atmospheric CO₂ inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate. Biogeosciences, 16 (1). pp. 117-134. ISSN 1726-4170.

[img] PDF - Published Version
Creative Commons Attribution.

[img] PDF (Corrigendum) - Erratum
Creative Commons Attribution.

[img] PDF - Supplemental Material
Creative Commons Attribution.


Use this Persistent URL to link to this item:


We have compared a suite of recent global CO₂ atmospheric inversion results to independent airborne observations and to each other, to assess their dependence on differences in northern extratropical (NET) vertical transport and to identify some of the drivers of model spread. We evaluate posterior CO₂ concentration profiles against observations from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft campaigns over the mid-Pacific in 2009–2011. Although the models differ in inverse approaches, assimilated observations, prior fluxes, and transport models, their broad latitudinal separation of land fluxes has converged significantly since the Atmospheric Carbon Cycle Inversion Intercomparison (TransCom 3) and the REgional Carbon Cycle Assessment and Processes (RECCAP) projects, with model spread reduced by 80 % since TransCom 3 and 70 % since RECCAP. Most modeled CO₂ fields agree reasonably well with the HIPPO observations, specifically for the annual mean vertical gradients in the Northern Hemisphere. Northern Hemisphere vertical mixing no longer appears to be a dominant driver of northern versus tropical (T) annual flux differences. Our newer suite of models still gives northern extratropical land uptake that is modest relative to previous estimates (Gurney et al., 2002; Peylin et al., 2013) and near-neutral tropical land uptake for 2009–2011. Given estimates of emissions from deforestation, this implies a continued uptake in intact tropical forests that is strong relative to historical estimates (Gurney et al., 2002; Peylin et al., 2013). The results from these models for other time periods (2004–2014, 2001–2004, 1992–1996) and re-evaluation of the TransCom 3 Level 2 and RECCAP results confirm that tropical land carbon fluxes including deforestation have been near neutral for several decades. However, models still have large disagreements on ocean–land partitioning. The fossil fuel (FF) and the atmospheric growth rate terms have been thought to be the best-known terms in the global carbon budget, but we show that they currently limit our ability to assess regional-scale terrestrial fluxes and ocean–land partitioning from the model ensemble.

Item Type:Article
Related URLs:
URLURL TypeDescription
Gaubert, Benjamin0000-0002-6595-0686
Stephens, Britton B.0000-0002-1966-6182
Basu, Sourish0000-0001-8605-5894
Chevallier, Frédéric0000-0002-4327-3813
Deng, Feng0000-0002-1381-0243
Kort, Eric A.0000-0003-4940-7541
Patra, Prabir K.0000-0001-5700-9389
Peters, Wouter0000-0001-8166-2070
Rödenbeck, Christian0000-0001-6011-6249
Saeki, Tazu0000-0003-1900-1786
Schimel, David0000-0003-3473-8065
Van der Laan-Luijkx, Ingrid0000-0002-3990-6737
Wofsy, Steven0000-0002-3990-6737
Yin, Yi0000-0003-4750-4997
Additional Information:© 2019 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License. Received: 20 Aug 2018 – Discussion started: 30 Aug 2018 – Revised: 11 Dec 2018 – Accepted: 14 Dec 2018 – Published: 16 Jan 2019. Data availability. The HIPPO dataset is available online (Wofsy et al., 2011, The supplement related to this article is available online at: Author contributions. BG, BS, and DS designed the study. BG and BS analyzed the simulations and observations and wrote the manuscript. SB, FC, FD, PKP, WP, CR, TS, IvdLL, and YY ran the atmospheric inversion calculations, provided results, and helped in the analysis of their model outputs. EK and SW provided the CO2 observations and guidance on their interpretation. All the authors provided feedback on the manuscript. The authors declare that they have no conflict of interest. Special issue statement. This article is part of the special issue “The 10th International Carbon Dioxide Conference (ICDC10) and the 19th WMO/IAEA Meeting on Carbon Dioxide, other Greenhouse Gases and Related Measurement Techniques (GGMT-2017) (AMT/ACP/BG/CP/ESD inter-journal SI)”. It is a result of the 10th International Carbon Dioxide Conference, Interlaken, Switzerland, 21–25 August 2017. We thank the entire HIPPO team for making these measurements possible and available. We gratefully acknowledge all the hard work that went into collecting and cross-validating the HIPPO CO₂ dataset: for the Harvard QCLS and OMS instruments by Bruce Daube, Greg Santoni, Jasna Pittman, Rodrigo Jimènez-Pizarro, Roisin Commane, Bin Xiang, and Sunyoung Park; for the NCAR AO2 instrument and NCAR/Scripps Medusa flask sampler by Ralph Keeling, Jonathan Bent, Andrew Watt, and Stephen Shertz; and for the NOAA PFP sampler by Colm Sweeney, Fred Moore, Ben Miller, Steve Montzka, Eric Hintsa, Jim Elkins, and Sonja Wolter. We would like to thank Andrew Jacobson for helping in the analysis of the CarbonTracker results and the entire CarbonTracker team. CarbonTracker CT2016 and CarbonTracker CT2017 results are provided by NOAA ESRL, Boulder, Colorado, USA, from the website at (last access: 7 January 2019). The National Center for Atmospheric Research is sponsored by the National Science Foundation. This work was supported by NASA ROSES grant NNX15AG87G. Frédéric Chevallier is funded by the Copernicus Atmosphere Monitoring Service, implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Commission, and was granted access to the HPC resources of TGCC under the allocation A0030102201. Prabir K. Patra and Tazu Saeki are partly supported by Japan Environment Research and Technology Development Fund of the Ministry of the Environment (grant no. 2-1701, 2-1401). Feng Deng was supported by Environment and Climate Change Canada (ECCC) and Canada Space Agency (CSA). Edited by: Paul Stoy. Reviewed by: Rachel Law and Ashley Ballantyne.
Funding AgencyGrant Number
Copernicus Atmosphere Monitoring ServiceUNSPECIFIED
European Centre for Medium-Range Weather Forecasts (ECMWF)UNSPECIFIED
European CommissionUNSPECIFIED
Environment and Climate Change Canada (ECCC)UNSPECIFIED
Ministry of the Environment (Japan)2-1701
Ministry of the Environment (Japan)2-1401
Canadian Space Agency (CSA)UNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20191118-082804838
Persistent URL:
Official Citation:Gaubert, B., Stephens, B. B., Basu, S., Chevallier, F., Deng, F., Kort, E. A., Patra, P. K., Peters, W., Rödenbeck, C., Saeki, T., Schimel, D., Van der Laan-Luijkx, I., Wofsy, S., and Yin, Y.: Global atmospheric CO2 inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate, Biogeosciences, 16, 117–134,, 2019
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99889
Deposited By: Tony Diaz
Deposited On:18 Nov 2019 18:13
Last Modified:18 Nov 2019 18:13

Repository Staff Only: item control page