Chemical Feedback From Decreasing Carbon Monoxide Emissions

B. Gaubert, H. M. Worden, A. F. J. Arellano, L. K. Emmons, S. Tilmes, J. Barre, S. Martinez Alonso, F. Vitt, J. L. Anderson, F. Alkemade, S. Houweling, D. P. Edwards

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Abstract

Understanding changes in the burden and growth rate of atmospheric methane (CH4) has been the focus of several recent studies but still lacks scientific consensus. Here we investigate the role of decreasing anthropogenic carbon monoxide (CO) emissions since 2002 on hydroxyl radical (OH) sinks and tropospheric CH4 loss. We quantify this impact by contrasting two model simulations for 2002–2013: (1) a Measurement of the Pollution in the Troposphere (MOPITT) CO reanalysis and (2) a Control-Run without CO assimilation. These simulations are performed with the Community Atmosphere Model with Chemistry of the Community Earth System Model fully coupled chemistry climate model with prescribed CH4 surface concentrations. The assimilation of MOPITT observations constrains the global CO burden, which significantly decreased over this period by ~20%. We find that this decrease results to (a) increase in CO chemical production, (b) higher CH4 oxidation by OH, and (c) ~8% shorter CH4 lifetime. We elucidate this coupling by a surrogate mechanism for CO-OH-CH4 that is quantified from the full chemistry simulations.

Original languageEnglish
Pages (from-to)9985-9995
Number of pages11
JournalGeophysical Research Letters
Volume44
Issue number19
Early online date13 Sept 2017
DOIs
Publication statusPublished - 16 Oct 2017

Funding

The NCAR MOPITT project is supported by the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) Program. MOPITT data are available at https://www2.acom.ucar. edu/mopitt. Computing resources were provided by the Climate Simulation Laboratory at NCAR’s Computational and Information Systems Laboratory (CISL), sponsored by the National Science Foundation and other agencies. We would like to acknowledge high- performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR’s Computational and Information Systems Laboratory (Computational and Information Systems Laboratory, 2012), sponsored by the National Science Foundation. CESM is sponsored by the National Science Foundation (NSF) and the U.S. Department of Energy (DOE). Administration of the CESM is main tained by the Climate and Global Dynamics Division (CGD) at the National Center for Atmospheric Research (NCAR). The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. A. F. Arellano acknowledges NASA support under grant NNX13AK24G. Ben Gaubert would like to thank Kevin Raeder, Nancy Collins, and the DART team for their help as well as Mijeong Park and Geoff Tyndall for their comments.

FundersFunder number
National Science Foundation
U.S. Department of EnergyNNX13AK24G
National Aeronautics and Space Administration

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