Global and Regional CH4 Emissions for 1995–2013 Derived From Atmospheric CH4, δ13C-CH4, and δD-CH4 Observations and a Chemical Transport Model

Ryo Fujita; Shinji Morimoto; Shamil Maksyutov; Heon Sook Kim; Mikhail Arshinov; Gordon Brailsford; Shuji Aoki; Takakiyo Nakazawa

doi:10.1029/2020JD032903

Global and Regional CH₄ Emissions for 1995–2013 Derived From Atmospheric CH₄, δ¹³C-CH₄, and δD-CH₄ Observations and a Chemical Transport Model

Ryo Fujita, Shinji Morimoto, Shamil Maksyutov, Heon Sook Kim, Mikhail Arshinov, Gordon Brailsford, Shuji Aoki, Takakiyo Nakazawa

SCI - Center for Atmospheric and Oceanic Studies

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

Abstract

To better understand the current global CH₄ budget, biogenic, fossil fuel, and biomass burning CH₄ fluxes for the period 1995–2013 were inversely estimated from the observed mole fraction data of atmospheric CH₄ using a three-dimensional chemical transport model. Then, forward simulations of carbon and hydrogen isotope ratios of atmospheric CH₄ (δ¹³C-CH₄ and δD-CH₄) were conducted using the inversion fluxes to evaluate the source proportion of the global total CH₄ emission. Model-simulated spatiotemporal variations of atmospheric CH₄ reproduce the observational results well; however, the simulated δ¹³C-CH₄ and δD-CH₄ values significantly underestimate their observed values as a whole. This implies that the proportion of biogenic CH₄ sources in the global CH₄ emission, deduced by inverse modeling, is overestimated, although the proportion is fairly comparable with the medians of recent multiple CH₄ inverse modeling. To reduce the disagreement between the observed and calculated isotope ratios, the CH₄ fluxes of individual source categories were adjusted using our atmospheric δ¹³C-CH₄ and δD-CH₄ data observed at Arctic and Antarctic surface stations. The resultant global average biogenic, fossil fuel, and biomass burning CH₄ fluxes over 2003–2012 are 346 ± 11, 162 ± 2, and 50 ± 2 TgCH₄ year⁻¹, respectively. It is also strongly suggested that the leveling-off of atmospheric CH₄ in the early 2000s and the renewed growth after 2006/2007 are, respectively, explainable by the decrease in biogenic and biomass burning CH₄ emissions for 2000–2006 and the increase in biogenic CH₄ emissions after that period. These emission changes mainly originate in the tropics.

Original language	English
Article number	e2020JD032903
Journal	Journal of Geophysical Research: Atmospheres
Volume	125
Issue number	14
DOIs	https://doi.org/10.1029/2020JD032903
Publication status	Published - 2020 Jul 27

Keywords

chemical transport model
global methane budget
isotope ratio
methane
mole fraction

ASJC Scopus subject areas

Geophysics
Forestry
Oceanography
Aquatic Science
Ecology
Water Science and Technology
Soil Science
Geochemistry and Petrology
Earth-Surface Processes
Atmospheric Science
Earth and Planetary Sciences (miscellaneous)
Space and Planetary Science
Palaeontology

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Fujita, R., Morimoto, S., Maksyutov, S., Kim, H. S., Arshinov, M., Brailsford, G., Aoki, S., & Nakazawa, T. (2020). Global and Regional CH₄ Emissions for 1995–2013 Derived From Atmospheric CH₄, δ¹³C-CH₄, and δD-CH₄ Observations and a Chemical Transport Model. Journal of Geophysical Research: Atmospheres, 125(14), [e2020JD032903]. https://doi.org/10.1029/2020JD032903

Global and Regional CH₄ Emissions for 1995–2013 Derived From Atmospheric CH₄, δ¹³C-CH₄, and δD-CH₄ Observations and a Chemical Transport Model. / Fujita, Ryo; Morimoto, Shinji; Maksyutov, Shamil; Kim, Heon Sook; Arshinov, Mikhail; Brailsford, Gordon; Aoki, Shuji; Nakazawa, Takakiyo.

In: Journal of Geophysical Research: Atmospheres, Vol. 125, No. 14, e2020JD032903, 27.07.2020.

Research output: Contribution to journal › Article › peer-review

Fujita, Ryo ; Morimoto, Shinji ; Maksyutov, Shamil ; Kim, Heon Sook ; Arshinov, Mikhail ; Brailsford, Gordon ; Aoki, Shuji ; Nakazawa, Takakiyo. / Global and Regional CH₄ Emissions for 1995–2013 Derived From Atmospheric CH₄, δ¹³C-CH₄, and δD-CH₄ Observations and a Chemical Transport Model. In: Journal of Geophysical Research: Atmospheres. 2020 ; Vol. 125, No. 14.

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title = "Global and Regional CH4 Emissions for 1995–2013 Derived From Atmospheric CH4, δ13C-CH4, and δD-CH4 Observations and a Chemical Transport Model",

abstract = "To better understand the current global CH4 budget, biogenic, fossil fuel, and biomass burning CH4 fluxes for the period 1995–2013 were inversely estimated from the observed mole fraction data of atmospheric CH4 using a three-dimensional chemical transport model. Then, forward simulations of carbon and hydrogen isotope ratios of atmospheric CH4 (δ13C-CH4 and δD-CH4) were conducted using the inversion fluxes to evaluate the source proportion of the global total CH4 emission. Model-simulated spatiotemporal variations of atmospheric CH4 reproduce the observational results well; however, the simulated δ13C-CH4 and δD-CH4 values significantly underestimate their observed values as a whole. This implies that the proportion of biogenic CH4 sources in the global CH4 emission, deduced by inverse modeling, is overestimated, although the proportion is fairly comparable with the medians of recent multiple CH4 inverse modeling. To reduce the disagreement between the observed and calculated isotope ratios, the CH4 fluxes of individual source categories were adjusted using our atmospheric δ13C-CH4 and δD-CH4 data observed at Arctic and Antarctic surface stations. The resultant global average biogenic, fossil fuel, and biomass burning CH4 fluxes over 2003–2012 are 346 ± 11, 162 ± 2, and 50 ± 2 TgCH4 year−1, respectively. It is also strongly suggested that the leveling-off of atmospheric CH4 in the early 2000s and the renewed growth after 2006/2007 are, respectively, explainable by the decrease in biogenic and biomass burning CH4 emissions for 2000–2006 and the increase in biogenic CH4 emissions after that period. These emission changes mainly originate in the tropics.",

keywords = "chemical transport model, global methane budget, isotope ratio, methane, mole fraction",

author = "Ryo Fujita and Shinji Morimoto and Shamil Maksyutov and Kim, {Heon Sook} and Mikhail Arshinov and Gordon Brailsford and Shuji Aoki and Takakiyo Nakazawa",

note = "Funding Information: We express our sincere thanks to Taku Umezawa, NIES for providing us with the ?13C-CH4 and ?D-CH4 data measured at TU. We are grateful to Hiroko Nagamoto and Mitsuyo Umeda, NIPR and Junko Miyakozawa, TU for their support of isotopes and CH4 analyses. We also appreciate Edward J. Dlugokencky, National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL), Motoki Sasakawa and Toshinobu Machida, NIES, Douglas E. J. Worthy, Environment and Climate Change Canada (ECCC), Ray Langenfelds, Paul Steele, and Paul Krummel, Commonwealth Scientific and Industrial Research Organization (CSIRO), Kazuyuki Saito, Japan Meteorological Agency (JMA), Rowena Moss and Sylvia Nichol, National Institute of Water and Atmospheric Research (NIWA), Emilio Cuevas-Agull?, Agencia Estatal de Meteorolog?a (AEMET), Salvatore Piacentino and Damiano Sferlazzo, Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Juha Hatakka, Finnish Meteorological Institute (FMI), Nina Paramonova, Main Geophysical Observatory (MGO), Taekyu Kim, National Institute of Environmental Research (NIER), Francesco Apadula, Ricerca sul Sistema Energetico (RSE), and Casper Labuschagne, South African Weather Service (SAWS), for providing us with the atmospheric CH4 data. We also thank James White, Bruce H. Vaughn, and Sylvia Michel, Institute of Arctic and Alpine Research, University of Colorado (INSTAAR) for providing us with the ?13C-CH4 and ?D-CH4 data. We further thank Tazu Saeki and Masako Senda who made contribution to developing the NIES-TM CH4 inverse model setup. This work was partly supported by NIPR through the Project Research KP-15 and KP-304, and by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, through the Arctic Challenge for Sustainability (ArCS) project, the JSPS KAKENHI Grants 23310012 and 15H03722, and the Program for Leading Graduate Schools, ?Inter-Graduate School Doctoral Degree Program on Global Safety.?",

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T1 - Global and Regional CH4 Emissions for 1995–2013 Derived From Atmospheric CH4, δ13C-CH4, and δD-CH4 Observations and a Chemical Transport Model

AU - Fujita, Ryo

AU - Morimoto, Shinji

AU - Maksyutov, Shamil

AU - Kim, Heon Sook

AU - Arshinov, Mikhail

AU - Brailsford, Gordon

AU - Aoki, Shuji

AU - Nakazawa, Takakiyo

N1 - Funding Information: We express our sincere thanks to Taku Umezawa, NIES for providing us with the ?13C-CH4 and ?D-CH4 data measured at TU. We are grateful to Hiroko Nagamoto and Mitsuyo Umeda, NIPR and Junko Miyakozawa, TU for their support of isotopes and CH4 analyses. We also appreciate Edward J. Dlugokencky, National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL), Motoki Sasakawa and Toshinobu Machida, NIES, Douglas E. J. Worthy, Environment and Climate Change Canada (ECCC), Ray Langenfelds, Paul Steele, and Paul Krummel, Commonwealth Scientific and Industrial Research Organization (CSIRO), Kazuyuki Saito, Japan Meteorological Agency (JMA), Rowena Moss and Sylvia Nichol, National Institute of Water and Atmospheric Research (NIWA), Emilio Cuevas-Agull?, Agencia Estatal de Meteorolog?a (AEMET), Salvatore Piacentino and Damiano Sferlazzo, Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Juha Hatakka, Finnish Meteorological Institute (FMI), Nina Paramonova, Main Geophysical Observatory (MGO), Taekyu Kim, National Institute of Environmental Research (NIER), Francesco Apadula, Ricerca sul Sistema Energetico (RSE), and Casper Labuschagne, South African Weather Service (SAWS), for providing us with the atmospheric CH4 data. We also thank James White, Bruce H. Vaughn, and Sylvia Michel, Institute of Arctic and Alpine Research, University of Colorado (INSTAAR) for providing us with the ?13C-CH4 and ?D-CH4 data. We further thank Tazu Saeki and Masako Senda who made contribution to developing the NIES-TM CH4 inverse model setup. This work was partly supported by NIPR through the Project Research KP-15 and KP-304, and by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, through the Arctic Challenge for Sustainability (ArCS) project, the JSPS KAKENHI Grants 23310012 and 15H03722, and the Program for Leading Graduate Schools, ?Inter-Graduate School Doctoral Degree Program on Global Safety.?

PY - 2020/7/27

Y1 - 2020/7/27

N2 - To better understand the current global CH4 budget, biogenic, fossil fuel, and biomass burning CH4 fluxes for the period 1995–2013 were inversely estimated from the observed mole fraction data of atmospheric CH4 using a three-dimensional chemical transport model. Then, forward simulations of carbon and hydrogen isotope ratios of atmospheric CH4 (δ13C-CH4 and δD-CH4) were conducted using the inversion fluxes to evaluate the source proportion of the global total CH4 emission. Model-simulated spatiotemporal variations of atmospheric CH4 reproduce the observational results well; however, the simulated δ13C-CH4 and δD-CH4 values significantly underestimate their observed values as a whole. This implies that the proportion of biogenic CH4 sources in the global CH4 emission, deduced by inverse modeling, is overestimated, although the proportion is fairly comparable with the medians of recent multiple CH4 inverse modeling. To reduce the disagreement between the observed and calculated isotope ratios, the CH4 fluxes of individual source categories were adjusted using our atmospheric δ13C-CH4 and δD-CH4 data observed at Arctic and Antarctic surface stations. The resultant global average biogenic, fossil fuel, and biomass burning CH4 fluxes over 2003–2012 are 346 ± 11, 162 ± 2, and 50 ± 2 TgCH4 year−1, respectively. It is also strongly suggested that the leveling-off of atmospheric CH4 in the early 2000s and the renewed growth after 2006/2007 are, respectively, explainable by the decrease in biogenic and biomass burning CH4 emissions for 2000–2006 and the increase in biogenic CH4 emissions after that period. These emission changes mainly originate in the tropics.

AB - To better understand the current global CH4 budget, biogenic, fossil fuel, and biomass burning CH4 fluxes for the period 1995–2013 were inversely estimated from the observed mole fraction data of atmospheric CH4 using a three-dimensional chemical transport model. Then, forward simulations of carbon and hydrogen isotope ratios of atmospheric CH4 (δ13C-CH4 and δD-CH4) were conducted using the inversion fluxes to evaluate the source proportion of the global total CH4 emission. Model-simulated spatiotemporal variations of atmospheric CH4 reproduce the observational results well; however, the simulated δ13C-CH4 and δD-CH4 values significantly underestimate their observed values as a whole. This implies that the proportion of biogenic CH4 sources in the global CH4 emission, deduced by inverse modeling, is overestimated, although the proportion is fairly comparable with the medians of recent multiple CH4 inverse modeling. To reduce the disagreement between the observed and calculated isotope ratios, the CH4 fluxes of individual source categories were adjusted using our atmospheric δ13C-CH4 and δD-CH4 data observed at Arctic and Antarctic surface stations. The resultant global average biogenic, fossil fuel, and biomass burning CH4 fluxes over 2003–2012 are 346 ± 11, 162 ± 2, and 50 ± 2 TgCH4 year−1, respectively. It is also strongly suggested that the leveling-off of atmospheric CH4 in the early 2000s and the renewed growth after 2006/2007 are, respectively, explainable by the decrease in biogenic and biomass burning CH4 emissions for 2000–2006 and the increase in biogenic CH4 emissions after that period. These emission changes mainly originate in the tropics.

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KW - global methane budget

KW - isotope ratio

KW - methane

KW - mole fraction

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