Regional Methane Emission Estimation Based on Observed Atmospheric Concentrations (2002-2012)

Prabir K. PATRA; Tazu SAEKI; Edward J. DLUGOKENCKY; Kentaro ISHIJIMA; Taku UMEZAWA; Akihiko ITO; Shuji AOKI; Shinji MORIMOTO; Eric A. KORT; Andrew CROTWELL; Kunchala RAVI KUMAR; Takakiyo NAKAZAWA

doi:10.2151/jmsj.2016-006

Journal of the Meteorological Society of Japan. Ser. II

Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165

Articles

Regional Methane Emission Estimation Based on Observed Atmospheric Concentrations (2002-2012)

Prabir K. PATRA, Tazu SAEKI, Edward J. DLUGOKENCKY, Kentaro ISHIJIMA, Taku UMEZAWA, Akihiko ITO, Shuji AOKI, Shinji MORIMOTO, Eric A. KORT, Andrew CROTWELL, Kunchala RAVI KUMAR, Takakiyo NAKAZAWA

Author information

Prabir K. PATRA
Department of Environmental Geochemical Cycle Research, JAMSTEC, Yokohama, Japan
CAOS, Graduate School of Science, Tohoku University, Sendai, Japan
Tazu SAEKI
Department of Environmental Geochemical Cycle Research, JAMSTEC, Yokohama, Japan
Edward J. DLUGOKENCKY
NOAA Earth System Research Laboratory, Colorado, USA
Kentaro ISHIJIMA
Department of Environmental Geochemical Cycle Research, JAMSTEC, Yokohama, Japan
Taku UMEZAWA
National Institute for Environmental Studies, Tsukuba, Japan
Akihiko ITO
Department of Environmental Geochemical Cycle Research, JAMSTEC, Yokohama, Japan
National Institute for Environmental Studies, Tsukuba, Japan
Shuji AOKI
CAOS, Graduate School of Science, Tohoku University, Sendai, Japan
Shinji MORIMOTO
CAOS, Graduate School of Science, Tohoku University, Sendai, Japan
Eric A. KORT
University of Michigan, Michigan, USA
Andrew CROTWELL
NOAA Earth System Research Laboratory, Colorado, USA
CIRES, University of Colorado Boulder, Colorado, USA
Kunchala RAVI KUMAR
Department of Environmental Geochemical Cycle Research, JAMSTEC, Yokohama, Japan
Arctic GRENE, National Institute of Polar Research, Tachikawa, Japan
Takakiyo NAKAZAWA
CAOS, Graduate School of Science, Tohoku University, Sendai, Japan

Corresponding author

ORCID

Keywords: global and regional methane budget, chemistry-transport model, inverse model

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Supplementary material

2016 Volume 94 Issue 1 Pages 91-113

DOI https://doi.org/10.2151/jmsj.2016-006

Details

Published: 2016 Received: July 11, 2015 Released on J-STAGE: March 08, 2016 Accepted: November 04, 2015 Advance online publication: - Revised: -

Abstract

Methane (CH₄) plays important roles in atmospheric chemistry and short-term forcing of climate. A clear understanding of atmospheric CH₄’s budget of emissions and losses is required to aid sustainable management of Earth’s future environment. We used an atmospheric chemistry-transport model (JAMSTEC’s ACTM) for simulating atmospheric CH₄. A global inverse modeling system has been developed for estimating CH₄ emissions from 53 land regions for 2002-2012 using measurements at 39 sites. An ensemble of 7 inversions is performed by varying a priori emissions. Global net CH₄ emissions varied between 505-509 and 524-545 Tg yr^-1 during 2002-2006 and 2008-2012, respectively (ranges based on 7 inversion cases), with a step like increase in 2007 in agreement with atmospheric measurements. The inversion system did not account for interannual variations in OH radicals reacting with CH₄ in the atmosphere. Our results suggest that the recent update of the EDGAR inventory (version 4.2FT2010) overestimated the global total emissions by at least 25 Tg yr^-1 in 2010. The increase in CH₄ emission since 2004 originated in the tropical and southern hemisphere regions, coinciding with an increase in non-dairy cattle stocks by ∼10 % from 2002 (with 1056 million heads) to 2012, leading to ∼10 Tg yr^-1 increase in emissions from enteric fermentation. All 7 ensemble cases robustly estimated the interannual variations in emissions, but poorly constrained the seasonal cycle amplitude or phase consistently for all regions due to the sparse observational network. Forward simulation results using both a priori and a posteriori emissions are compared with independent aircraft measurements for validation. Based on the results of the comparison, we reject the upper limit (545 Tg yr^-1) of global total emissions as 14 Tg yr^-1 too high during 2008-2012, which allows us to further conclude that the increase in CH₄ emissions over the East Asia (mainly China) region was 7-8 Tg yr^-1 between the 2002-2006 and 2008-2012 periods, contrary to 1-17 Tg yr^-1 in the a priori emissions.

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