Articles | Volume 25, issue 19
https://doi.org/10.5194/acp-25-12513-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-25-12513-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
09 Oct 2025
Research article |
| 09 Oct 2025
| 09 Oct 2025
Evaluating urban methane emissions and their attributes in a megacity, Osaka, Japan, via mobile and eddy covariance measurements
Graduate School of Agriculture, Osaka Metropolitan University, Sakai, 599-8531, Japan
Taku Umezawa
National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Yukio Terao
National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Mark Lunt
Environmental Defense Fund, New York, NY 10010, USA
James Lawrence France
Environmental Defense Fund, New York, NY 10010, USA
Earth Sciences Dept, Royal Holloway University of London, TW20 0EQ, Egham, UK
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Qing Ying, Benjamin Poulter, Jennifer D. Watts, Kyle A. Arndt, Anna-Maria Virkkala, Lori Bruhwiler, Youmi Oh, Brendan M. Rogers, Susan M. Natali, Hilary Sullivan, Amanda Armstrong, Eric J. Ward, Luke D. Schiferl, Clayton D. Elder, Olli Peltola, Annett Bartsch, Ankur R. Desai, Eugénie Euskirchen, Mathias Göckede, Bernhard Lehner, Mats B. Nilsson, Matthias Peichl, Oliver Sonnentag, Eeva-Stiina Tuittila, Torsten Sachs, Aram Kalhori, Masahito Ueyama, and Zhen Zhang
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In April–May 2019 we carried out an airborne field campaign in the southern North Sea with the aim of studying methane emissions of offshore gas installations. We determined methane emissions from elevated methane measured downstream of the sampled installations. We compare our measured methane emissions with estimated methane emissions from national and global annual inventories. As a result, we find inconsistencies of inventories and large discrepancies between measurements and inventories.
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Preprint archived
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We are focused on verification of δ13CH4 measurements in near-source conditions and we have provided an insight into the impact of chosen calculation methods for determined isotopic signatures. Our study offers a step forward for establishing an unified, robust, and reliable analytical technique to determine δ13CH4 of methane sources. Our recommended analytical approach reduces biases and uncertainties coming from measurement conditions, data clustering and various available fitting methods.
Liang Feng, Paul I. Palmer, Robert J. Parker, Mark F. Lunt, and Hartmut Bösch
Atmos. Chem. Phys., 23, 4863–4880, https://doi.org/10.5194/acp-23-4863-2023, https://doi.org/10.5194/acp-23-4863-2023, 2023
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Our understanding of recent changes in atmospheric methane has defied explanation. Since 2007, the atmospheric growth of methane has accelerated to record-breaking values in 2020 and 2021. We use satellite observations of methane to show that (1) increasing emissions over the tropics are mostly responsible for these recent atmospheric changes, and (2) changes in the OH sink during the 2020 Covid-19 lockdown can explain up to 34% of changes in atmospheric methane for that year.
Robert J. Parker, Chris Wilson, Edward Comyn-Platt, Garry Hayman, Toby R. Marthews, A. Anthony Bloom, Mark F. Lunt, Nicola Gedney, Simon J. Dadson, Joe McNorton, Neil Humpage, Hartmut Boesch, Martyn P. Chipperfield, Paul I. Palmer, and Dai Yamazaki
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Wetlands are the largest natural source of methane, one of the most important climate gases. The JULES land surface model simulates these emissions. We use satellite data to evaluate how well JULES reproduces the methane seasonal cycle over different tropical wetlands. It performs well for most regions; however, it struggles for some African wetlands influenced heavily by river flooding. We explain the reasons for these deficiencies and highlight how future development will improve these areas.
Bryce F. J. Kelly, Xinyi Lu, Stephen J. Harris, Bruno G. Neininger, Jorg M. Hacker, Stefan Schwietzke, Rebecca E. Fisher, James L. France, Euan G. Nisbet, David Lowry, Carina van der Veen, Malika Menoud, and Thomas Röckmann
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Malika Menoud, Carina van der Veen, Dave Lowry, Julianne M. Fernandez, Semra Bakkaloglu, James L. France, Rebecca E. Fisher, Hossein Maazallahi, Mila Stanisavljević, Jarosław Nęcki, Katarina Vinkovic, Patryk Łakomiec, Janne Rinne, Piotr Korbeń, Martina Schmidt, Sara Defratyka, Camille Yver-Kwok, Truls Andersen, Huilin Chen, and Thomas Röckmann
Earth Syst. Sci. Data, 14, 4365–4386, https://doi.org/10.5194/essd-14-4365-2022, https://doi.org/10.5194/essd-14-4365-2022, 2022
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Emission sources of methane (CH4) can be distinguished with measurements of CH4 stable isotopes. We present new measurements of isotope signatures of various CH4 sources in Europe, mainly anthropogenic, sampled from 2017 to 2020. The present database also contains the most recent update of the global signature dataset from the literature. The dataset improves CH4 source attribution and the understanding of the global CH4 budget.
Taku Umezawa, Satoshi Sugawara, Kenji Kawamura, Ikumi Oyabu, Stephen J. Andrews, Takuya Saito, Shuji Aoki, and Takakiyo Nakazawa
Atmos. Chem. Phys., 22, 6899–6917, https://doi.org/10.5194/acp-22-6899-2022, https://doi.org/10.5194/acp-22-6899-2022, 2022
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Greenhouse gas methane in the Arctic atmosphere has not been accurately reported for 1900–1980 from either direct observations or ice core reconstructions. By using trace gas data from firn (compacted snow layers above ice sheet), air samples at two Greenland sites, and a firn air transport model, this study suggests a likely range of the Arctic methane reconstruction for the 20th century. Atmospheric scenarios from two previous studies are also evaluated for consistency with the firn data sets.
Amy Foulds, Grant Allen, Jacob T. Shaw, Prudence Bateson, Patrick A. Barker, Langwen Huang, Joseph R. Pitt, James D. Lee, Shona E. Wilde, Pamela Dominutti, Ruth M. Purvis, David Lowry, James L. France, Rebecca E. Fisher, Alina Fiehn, Magdalena Pühl, Stéphane J. B. Bauguitte, Stephen A. Conley, Mackenzie L. Smith, Tom Lachlan-Cope, Ignacio Pisso, and Stefan Schwietzke
Atmos. Chem. Phys., 22, 4303–4322, https://doi.org/10.5194/acp-22-4303-2022, https://doi.org/10.5194/acp-22-4303-2022, 2022
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We measured CH4 emissions from 21 offshore oil and gas facilities in the Norwegian Sea in 2019. Measurements compared well with operator-reported emissions but were greatly underestimated when compared with a 2016 global fossil fuel inventory. This study demonstrates the need for up-to-date and accurate inventories for use in research and policy and the important benefits of best-practice reporting methods by operators. Airborne measurements are an effective tool to validate such inventories.
Alice E. Ramsden, Anita L. Ganesan, Luke M. Western, Matthew Rigby, Alistair J. Manning, Amy Foulds, James L. France, Patrick Barker, Peter Levy, Daniel Say, Adam Wisher, Tim Arnold, Chris Rennick, Kieran M. Stanley, Dickon Young, and Simon O'Doherty
Atmos. Chem. Phys., 22, 3911–3929, https://doi.org/10.5194/acp-22-3911-2022, https://doi.org/10.5194/acp-22-3911-2022, 2022
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Quantifying methane emissions from different sources is a key focus of current research. We present a method for estimating sectoral methane emissions that uses ethane as a tracer for fossil fuel methane. By incorporating variable ethane : methane emission ratios into this model, we produce emissions estimates with improved uncertainty characterisation. This method will be particularly useful for studying methane emissions in areas with complex distributions of sources.
Anna-Maria Virkkala, Susan M. Natali, Brendan M. Rogers, Jennifer D. Watts, Kathleen Savage, Sara June Connon, Marguerite Mauritz, Edward A. G. Schuur, Darcy Peter, Christina Minions, Julia Nojeim, Roisin Commane, Craig A. Emmerton, Mathias Goeckede, Manuel Helbig, David Holl, Hiroki Iwata, Hideki Kobayashi, Pasi Kolari, Efrén López-Blanco, Maija E. Marushchak, Mikhail Mastepanov, Lutz Merbold, Frans-Jan W. Parmentier, Matthias Peichl, Torsten Sachs, Oliver Sonnentag, Masahito Ueyama, Carolina Voigt, Mika Aurela, Julia Boike, Gerardo Celis, Namyi Chae, Torben R. Christensen, M. Syndonia Bret-Harte, Sigrid Dengel, Han Dolman, Colin W. Edgar, Bo Elberling, Eugenie Euskirchen, Achim Grelle, Juha Hatakka, Elyn Humphreys, Järvi Järveoja, Ayumi Kotani, Lars Kutzbach, Tuomas Laurila, Annalea Lohila, Ivan Mammarella, Yojiro Matsuura, Gesa Meyer, Mats B. Nilsson, Steven F. Oberbauer, Sang-Jong Park, Roman Petrov, Anatoly S. Prokushkin, Christopher Schulze, Vincent L. St. Louis, Eeva-Stiina Tuittila, Juha-Pekka Tuovinen, William Quinton, Andrej Varlagin, Donatella Zona, and Viacheslav I. Zyryanov
Earth Syst. Sci. Data, 14, 179–208, https://doi.org/10.5194/essd-14-179-2022, https://doi.org/10.5194/essd-14-179-2022, 2022
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The effects of climate warming on carbon cycling across the Arctic–boreal zone (ABZ) remain poorly understood due to the relatively limited distribution of ABZ flux sites. Fortunately, this flux network is constantly increasing, but new measurements are published in various platforms, making it challenging to understand the ABZ carbon cycle as a whole. Here, we compiled a new database of Arctic–boreal CO2 fluxes to help facilitate large-scale assessments of the ABZ carbon cycle.
Shohei Nomura, Manish Naja, M. Kawser Ahmed, Hitoshi Mukai, Yukio Terao, Toshinobu Machida, Motoki Sasakawa, and Prabir K. Patra
Atmos. Chem. Phys., 21, 16427–16452, https://doi.org/10.5194/acp-21-16427-2021, https://doi.org/10.5194/acp-21-16427-2021, 2021
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Long-term measurements of greenhouse gases (GHGs) in India and Bangladesh unveiled specific characteristics in their variations in these regions. Plants including rice cultivated in winter and summer strongly affected seasonal variations and levels in CO2 and CH4. Long-term variability of GHGs showed quite different features in their growth rates from those in Mauna Loa. GHG trends in this region seemed to be hardly affected by El Niño–Southern Oscillation (ENSO).
Mark F. Lunt, Alistair J. Manning, Grant Allen, Tim Arnold, Stéphane J.-B. Bauguitte, Hartmut Boesch, Anita L. Ganesan, Aoife Grant, Carole Helfter, Eiko Nemitz, Simon J. O'Doherty, Paul I. Palmer, Joseph R. Pitt, Chris Rennick, Daniel Say, Kieran M. Stanley, Ann R. Stavert, Dickon Young, and Matt Rigby
Atmos. Chem. Phys., 21, 16257–16276, https://doi.org/10.5194/acp-21-16257-2021, https://doi.org/10.5194/acp-21-16257-2021, 2021
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We present an evaluation of the UK's methane emissions between 2013 and 2020 using a network of tall tower measurement sites. We find emissions that are consistent in both magnitude and trend with the UK's reported emissions, with a declining trend driven by a decrease in emissions from England. The impact of various components of the modelling set-up on these findings are explored through a number of sensitivity studies.
Mehliyar Sadiq, Paul I. Palmer, Mark F. Lunt, Liang Feng, Ingrid Super, Stijn N. C. Dellaert, and Hugo A. C. Denier van der Gon
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-816, https://doi.org/10.5194/acp-2021-816, 2021
Publication in ACP not foreseen
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We make use of high-resolution emission inventory of CO2 and co-emitted tracers, satellite measurements, together with nested atmospheric transport model simulation, to investigate how reactive trace gases such as nitrogen dioxide and carbon monoxide can be used as proxies to determine the combustion contribution to atmospheric CO2 over Europe. We find stronger correlation in ratios of nitrogen dioxide and carbon dioxide between emission and satellite observed and modelled column concentration.
Kyle B. Delwiche, Sara Helen Knox, Avni Malhotra, Etienne Fluet-Chouinard, Gavin McNicol, Sarah Feron, Zutao Ouyang, Dario Papale, Carlo Trotta, Eleonora Canfora, You-Wei Cheah, Danielle Christianson, Ma. Carmelita R. Alberto, Pavel Alekseychik, Mika Aurela, Dennis Baldocchi, Sheel Bansal, David P. Billesbach, Gil Bohrer, Rosvel Bracho, Nina Buchmann, David I. Campbell, Gerardo Celis, Jiquan Chen, Weinan Chen, Housen Chu, Higo J. Dalmagro, Sigrid Dengel, Ankur R. Desai, Matteo Detto, Han Dolman, Elke Eichelmann, Eugenie Euskirchen, Daniela Famulari, Kathrin Fuchs, Mathias Goeckede, Sébastien Gogo, Mangaliso J. Gondwe, Jordan P. Goodrich, Pia Gottschalk, Scott L. Graham, Martin Heimann, Manuel Helbig, Carole Helfter, Kyle S. Hemes, Takashi Hirano, David Hollinger, Lukas Hörtnagl, Hiroki Iwata, Adrien Jacotot, Gerald Jurasinski, Minseok Kang, Kuno Kasak, John King, Janina Klatt, Franziska Koebsch, Ken W. Krauss, Derrick Y. F. Lai, Annalea Lohila, Ivan Mammarella, Luca Belelli Marchesini, Giovanni Manca, Jaclyn Hatala Matthes, Trofim Maximov, Lutz Merbold, Bhaskar Mitra, Timothy H. Morin, Eiko Nemitz, Mats B. Nilsson, Shuli Niu, Walter C. Oechel, Patricia Y. Oikawa, Keisuke Ono, Matthias Peichl, Olli Peltola, Michele L. Reba, Andrew D. Richardson, William Riley, Benjamin R. K. Runkle, Youngryel Ryu, Torsten Sachs, Ayaka Sakabe, Camilo Rey Sanchez, Edward A. Schuur, Karina V. R. Schäfer, Oliver Sonnentag, Jed P. Sparks, Ellen Stuart-Haëntjens, Cove Sturtevant, Ryan C. Sullivan, Daphne J. Szutu, Jonathan E. Thom, Margaret S. Torn, Eeva-Stiina Tuittila, Jessica Turner, Masahito Ueyama, Alex C. Valach, Rodrigo Vargas, Andrej Varlagin, Alma Vazquez-Lule, Joseph G. Verfaillie, Timo Vesala, George L. Vourlitis, Eric J. Ward, Christian Wille, Georg Wohlfahrt, Guan Xhuan Wong, Zhen Zhang, Donatella Zona, Lisamarie Windham-Myers, Benjamin Poulter, and Robert B. Jackson
Earth Syst. Sci. Data, 13, 3607–3689, https://doi.org/10.5194/essd-13-3607-2021, https://doi.org/10.5194/essd-13-3607-2021, 2021
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Methane is an important greenhouse gas, yet we lack knowledge about its global emissions and drivers. We present FLUXNET-CH4, a new global collection of methane measurements and a critical resource for the research community. We use FLUXNET-CH4 data to quantify the seasonality of methane emissions from freshwater wetlands, finding that methane seasonality varies strongly with latitude. Our new database and analysis will improve wetland model accuracy and inform greenhouse gas budgets.
Sara M. Defratyka, Jean-Daniel Paris, Camille Yver-Kwok, Daniel Loeb, James France, Jon Helmore, Nigel Yarrow, Valérie Gros, and Philippe Bousquet
Atmos. Meas. Tech., 14, 5049–5069, https://doi.org/10.5194/amt-14-5049-2021, https://doi.org/10.5194/amt-14-5049-2021, 2021
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We consider the possibility of using the CRDS Picarro G2201-i instrument, originally designed for isotopic CH4 and CO2, for measurements of ethane : methane in near-source conditions. The work involved laboratory tests, a controlled release experiment and mobile measurements. We show the potential of determining ethane : methane with 50 ppb ethane uncertainty. The instrument can correctly estimate the ratio in CH4 enhancements of 1 ppm and more, as can be found at strongly emitting sites.
Xinyi Lu, Stephen J. Harris, Rebecca E. Fisher, James L. France, Euan G. Nisbet, David Lowry, Thomas Röckmann, Carina van der Veen, Malika Menoud, Stefan Schwietzke, and Bryce F. J. Kelly
Atmos. Chem. Phys., 21, 10527–10555, https://doi.org/10.5194/acp-21-10527-2021, https://doi.org/10.5194/acp-21-10527-2021, 2021
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Many coal seam gas (CSG) facilities in the Surat Basin, Australia, are adjacent to other sources of methane, including agricultural, urban, and natural seeps. This makes it challenging to estimate the amount of methane being emitted into the atmosphere from CSG facilities. This research demonstrates that measurements of the carbon and hydrogen stable isotopic composition of methane can distinguish between and apportion methane emissions from CSG facilities, cattle, and many other sources.
Yosuke Niwa, Yousuke Sawa, Hideki Nara, Toshinobu Machida, Hidekazu Matsueda, Taku Umezawa, Akihiko Ito, Shin-Ichiro Nakaoka, Hiroshi Tanimoto, and Yasunori Tohjima
Atmos. Chem. Phys., 21, 9455–9473, https://doi.org/10.5194/acp-21-9455-2021, https://doi.org/10.5194/acp-21-9455-2021, 2021
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Fires in Equatorial Asia release a large amount of carbon into the atmosphere. Extensively using high-precision atmospheric carbon dioxide (CO2) data from a commercial aircraft observation project, we estimated fire carbon emissions in Equatorial Asia induced by the big El Niño event in 2015. Additional shipboard measurement data elucidated the validity of the analysis and the best estimate indicated 273 Tg C for fire emissions during September–October 2015.
Shona E. Wilde, Pamela A. Dominutti, Grant Allen, Stephen J. Andrews, Prudence Bateson, Stephane J.-B. Bauguitte, Ralph R. Burton, Ioana Colfescu, James France, James R. Hopkins, Langwen Huang, Anna E. Jones, Tom Lachlan-Cope, James D. Lee, Alastair C. Lewis, Stephen D. Mobbs, Alexandra Weiss, Stuart Young, and Ruth M. Purvis
Atmos. Chem. Phys., 21, 3741–3762, https://doi.org/10.5194/acp-21-3741-2021, https://doi.org/10.5194/acp-21-3741-2021, 2021
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We use airborne measurements to evaluate the speciation of volatile organic compound (VOC) emissions from offshore oil and gas (O&G) installations in the North Sea. The composition of emissions varied across regions associated with either gas, condensate or oil extraction, demonstrating that VOC emissions are not uniform across the whole O&G sector. We compare our results to VOC source profiles in the UK emissions inventory, showing these emissions are not currently fully characterized.
Max Thomas, James France, Odile Crabeck, Benjamin Hall, Verena Hof, Dirk Notz, Tokoloho Rampai, Leif Riemenschneider, Oliver John Tooth, Mathilde Tranter, and Jan Kaiser
Atmos. Meas. Tech., 14, 1833–1849, https://doi.org/10.5194/amt-14-1833-2021, https://doi.org/10.5194/amt-14-1833-2021, 2021
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We describe the Roland von Glasow Air-Sea-Ice Chamber, a laboratory facility for studying ocean–sea-ice–atmosphere interactions. We characterise the technical capabilities of our facility to help future users plan and perform experiments. We also characterise the sea ice grown in the facility, showing that the extinction of photosynthetically active radiation, the bulk salinity, and the growth rate of our artificial sea ice are within the range of natural values.
James L. France, Prudence Bateson, Pamela Dominutti, Grant Allen, Stephen Andrews, Stephane Bauguitte, Max Coleman, Tom Lachlan-Cope, Rebecca E. Fisher, Langwen Huang, Anna E. Jones, James Lee, David Lowry, Joseph Pitt, Ruth Purvis, John Pyle, Jacob Shaw, Nicola Warwick, Alexandra Weiss, Shona Wilde, Jonathan Witherstone, and Stuart Young
Atmos. Meas. Tech., 14, 71–88, https://doi.org/10.5194/amt-14-71-2021, https://doi.org/10.5194/amt-14-71-2021, 2021
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Measuring emission rates of methane from installations is tricky, and it is even more so when those installations are located offshore. Here, we show the aircraft set-up and demonstrate an effective methodology for surveying emissions from UK and Dutch offshore oil and gas installations. We present example data collected from two campaigns to demonstrate the challenges and solutions encountered during these surveys.
Yonghong Yi, John S. Kimball, Jennifer D. Watts, Susan M. Natali, Donatella Zona, Junjie Liu, Masahito Ueyama, Hideki Kobayashi, Walter Oechel, and Charles E. Miller
Biogeosciences, 17, 5861–5882, https://doi.org/10.5194/bg-17-5861-2020, https://doi.org/10.5194/bg-17-5861-2020, 2020
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We developed a 1 km satellite-data-driven permafrost carbon model to evaluate soil respiration sensitivity to recent snow cover changes in Alaska. Results show earlier snowmelt enhances growing-season soil respiration and reduces annual carbon uptake, while early cold-season soil respiration is linked to the number of snow-free days after the land surface freezes. Our results also show nonnegligible influences of subgrid variability in surface conditions on model-simulated CO2 seasonal cycles.
Cited articles
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Commane, R., Hallward-Driemeier, A., and Murray, L. T.: Intercomparison of commercial analyzers for atmospheric ethane and methane observations, Atmos. Meas. Tech., 16, 1431–1441, https://doi.org/10.5194/amt-16-1431-2023, 2023.
Crippa, M., Guizzardi, D., Pisoni, E., Solazzo, E., Guion, A., Muntean, M., Florczyk, A., Schiavina, M., Melchiorri, M., and Hutfilter, A. F.: Global anthropogenic emissions in urban areas: patterns, trends, and challenges, Environ. Res. Lett., 16, 074033, https://doi.org/10.1088/1748-9326/ac00e2, 2021.
Defratyka, S. M., Paris, J.-D., Yver-Kwok, C., Fernandez, J. M., Korben, P., and Bousquet, P.: Mapping urban methane sources in Paris, Fance, Environ. Sci. Technol., 55, 8583–8591, https://doi.org/10.1021/acs.est.1c00859, 2021.
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Gioli, B., Toscano, P., Zaldei, A., Fratini, G., and Miglietta, F.: CO2, CH4 and particles flux measurements in Florence, Italy, Enrgy. Proced., 40, 537–544, https://doi.org/10.1016/j.egypro.2013.08.062, 2013.
Helfter, C., Tremper, A. H., Halios, C. H., Kotthaus, S., Bjorkegren, A., Grimmond, C. S. B., Barlow, J. F., and Nemitz, E.: Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK, Atmos. Chem. Phys., 16, 10543–10557, https://doi.org/10.5194/acp-16-10543-2016, 2016.
Hopkins, F. M., Kort, E. A., Bush, S. E., Ehleringer, J. R., Lai, C.-T., Black, D. R., and Randerson, J. T.: Spatial patterns and source attribution of urban methane in the Los Angels Basin, J. Geophys. Res.-Atmos., 121, 2490–2507, https://doi.org/10.1002/2015JD024429, 2016.
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Lebel, E. D., Finnegan, C. J., Ouyang, Z., and Jackson, R. B.: Methane and NOx emissions from natural gas stoves, cooktops, and ovens in residential homes, Environ. Sci. Technol., 56, 2529–2539, https://doi.org/10.1021/acs.est.1c04707, 2022.
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Okamura, S., Ueyama, M., and Takahashi, K.: Temporal and spatial variations in NO2 fluxes by tall tower eddy covariance measurements over a dense urban center in Sakai, Japan, Atmos. Environ., 339, 120870, https://doi.org/10.1016/j.atmosenv.2024.120870, 2024.
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Phillips, N. G., Ackley, R., Crosson, E. R., Down, A., Hutyra, L. R., Brondfield, M., Karr, J. D., Zhao, K., and Jackson, R. B.: Mapping urban pipeline leaks: methane leaks across Boston, Environ. Pollut., 173, 1–4, https://doi.org/10.1016/j.envpol.2012.11.003, 2013.
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Short summary
Methane (CH4) emissions were measured in the megacity of Osaka, Japan, using mobile and eddy covariance methods. The CH4 emissions were much higher than those reported in local inventories, with natural gas contributing up to 74 % of the emissions. Several CH4 sources not accounted for in current inventories were identified. These results emphasize the need for more comprehensive emissions tracking in urban areas to enhance climate change mitigation efforts.
Methane (CH4) emissions were measured in the megacity of Osaka, Japan, using mobile and eddy...
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