TY - JOUR
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.?
Funding Information:
We express our sincere thanks to Taku Umezawa, NIES for providing us with the δC‐CH and δD‐CH data measured at TU. We are grateful to Hiroko Nagamoto and Mitsuyo Umeda, NIPR and Junko Miyakozawa, TU for their support of isotopes and CH 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‐Agulló, Agencia Estatal de Meteorología (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 CH 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 δC‐CH and δD‐CH data. We further thank Tazu Saeki and Masako Senda who made contribution to developing the NIES‐TM CH 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.” 13 4 4 4 4 13 4 4 4
Publisher Copyright:
©2020. The Authors.
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.
KW - chemical transport model
KW - global methane budget
KW - isotope ratio
KW - methane
KW - mole fraction
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U2 - 10.1029/2020JD032903
DO - 10.1029/2020JD032903
M3 - Article
AN - SCOPUS:85088568889
VL - 125
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
SN - 2169-897X
IS - 14
M1 - e2020JD032903
ER -