The Orbiting Carbon Observatory (OCO-2) tracks 2–3 peta-gram increase in carbon release to the atmosphere during the 2014–2016 El Niño

Creators: Patra, Prabir K.; Crisp, David; Kaiser, Johannes W.; Wunch, Debra; Saeki, Tazu; Ichii, Kazuhito; Sekiya, Takashi; Wennberg, Paul O.; Feist, Dietrich G.; Pollard, David F.; Griffith, David W. T.; Velazco, Voltaire A.; De Mazière, M.; Sha, Mahesh K.; Roehl, Coleen; Chatterjee, Abhishek; Ishijima, Kentaro

Abstract

The powerful El Niño event of 2015–2016 – the third most intense since the 1950s – has exerted a large impact on the Earth's natural climate system. The column-averaged CO_2 dry-air mole fraction (XCO_2) observations from satellites and ground-based networks are analyzed together with in situ observations for the period of September 2014 to October 2016. From the differences between satellite (OCO-2) observations and simulations using an atmospheric chemistry-transport model, we estimate that, relative to the mean annual fluxes for 2014, the most recent El Niño has contributed to an excess CO_2 emission from the Earth's surface (land + ocean) to the atmosphere in the range of 2.4 ± 0.2 PgC (1 Pg = 10^(15) g) over the period of July 2015 to June 2016. The excess CO_2 flux is resulted primarily from reduction in vegetation uptake due to drought, and to a lesser degree from increased biomass burning. It is about the half of the CO_2 flux anomaly (range: 4.4–6.7 PgC) estimated for the 1997/1998 El Niño. The annual total sink is estimated to be 3.9 ± 0.2 PgC for the assumed fossil fuel emission of 10.1 PgC. The major uncertainty in attribution arise from error in anthropogenic emission trends, satellite data and atmospheric transport.

Additional Information

© 2017 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received: 03 October 2016; Accepted: 25 September 2017; Published online: 19 October 2017. This work is supported by the Environment Research and Technology Development Fund (2–1401, 2–1701) of the Ministry of the Environment, Japan. PKP is grateful to Christopher O'Dell for sharing user-friendly OCO-2 and GOSAT data in NetCDF. This research has benefitted and inspired by discussions with Andrew Jacobson (also for NOAA CarbonTracker inversion fluxes), David Baker, Frederic Chevallier (also for CAMS inversion fluxes) and Sander Houweling. We thank Pieter Tans, Edward Dlugokencky and team members at NOAA ESRL for allowing us to use the in situ CO_2 measurements at the surface sites. The XCO_2 observation data were produced by the OCO-2 project at the Jet Propulsion Laboratory, California Institute of Technology, and obtained from the OCO-2 data archive maintained at the NASA Goddard Earth Science Data and Information Services Center. Part of the analysis described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The GFAS dataset was produced by EU's Copernicus Atmosphere Monitoring Service and distributed by the GEIA database ECCAD (http://eccad.sedoo.fr). The TCCON data were downloaded from the TCCON archive, hosted by CDIAC, at http://www.tccon.ornl.gov. The TCCON station on Ascension Island has been funded by the Max Planck Institute for Biogeochemistry. The TCCON site at Ile de la Réunion is operated by the Royal Belgian Institute for Space Aeronomy with financial support in 2014 and 2015 under the EU project ICOS_Inwire and the ministerial decree for ICOS (FR/35/IC2) and local activities supported by LACy/UMR8105 - Université de La Réunion. TCCON data from Park Falls, Lamont, and Darwin are made possible with support from NASA. TCCON data were obtained from the TCCON Data Archive, hosted by the Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A., http://tccon.ornl.gov. We thank both the three reviewers for critical but constructive comments, which have been very helpful for reshaping the contents of this article. Author Contributions: P.P., D.C. and J.K. conceived the experiments, P.P. conducted the model experiments and data analysis, D.C. provided guidance on the use of OCO-2 data, J.W. provided GFAS emissions, T.Sa. run ACTM inversions, T.Se. run tracer simulation, K.Ic. and A.C. supported data analysis, and D.W., P.W., D.F., D.P., D.G., V.V., M.D., M.S., C.R. provided TCCON measurements and supported analysis. K.Is. prepared JRA55 meteorology. All authors reviewed the manuscript and contributed to writing. The authors declare that they have no competing interests.

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