Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

Anita L. Ganesan*, Stefan Schwietzke, Benjamin Poulter, Tim Arnold, Xin Lan, Matt Rigby, Felix R. Vogel, Guido R. van der Werf, Greet Janssens-Maenhout, Hartmut Boesch, Sudhanshu Pandey, Alistair J. Manning, Robert B. Jackson, Euan G. Nisbet, Martin R. Manning

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The 2015 Paris Agreement of the United Nations Framework Convention on Climate Change aims to keep global average temperature increases well below 2 °C of preindustrial levels in the Year 2100. Vital to its success is achieving a decrease in the abundance of atmospheric methane (CH4), the second most important anthropogenic greenhouse gas. If this reduction is to be achieved, individual nations must make and meet reduction goals in their nationally determined contributions, with regular and independently verifiable global stock taking. Targets for the Paris Agreement have been set, and now the capability must follow to determine whether CH4 reductions are actually occurring. At present, however, there are significant limitations in the ability of scientists to quantify CH4 emissions accurately at global and national scales and to diagnose what mechanisms have altered trends in atmospheric mole fractions in the past decades. For example, in 2007, mole fractions suddenly started rising globally after a decade of almost no growth. More than a decade later, scientists are still debating the mechanisms behind this increase. This study reviews the main approaches and limitations in our current capability to diagnose the drivers of changes in atmospheric CH4 and, crucially, proposes ways to improve this capability in the coming decade. Recommendations include the following: (i) improvements to process-based models of the main sectors of CH4 emissions—proposed developments call for the expansion of tropical wetland flux measurements, bridging remote sensing products for improved measurement of wetland area and dynamics, expanding measurements of fossil fuel emissions at the facility and regional levels, expanding country-specific data on the composition of waste sent to landfill and the types of wastewater treatment systems implemented, characterizing and representing temporal profiles of crop growing seasons, implementing parameters related to ruminant emissions such as animal feed, and improving the detection of small fires associated with agriculture and deforestation; (ii) improvements to measurements of CH4 mole fraction and its isotopic variations—developments include greater vertical profiling at background sites, expanding networks of dense urban measurements with a greater focus on relatively poor countries, improving the precision of isotopic ratio measurements of 13CH4, CH3D, 14CH4, and clumped isotopes, creating isotopic reference materials for international-scale development, and expanding spatial and temporal characterization of isotopic source signatures; and (iii) improvements to inverse modeling systems to derive emissions from atmospheric measurements—advances are proposed in the areas of hydroxyl radical quantification, in systematic uncertainty quantification through validation of chemical transport models, in the use of source tracers for estimating sector-level emissions, and in the development of time and space resolved national inventories. These and other recommendations are proposed for the major areas of CH4 science with the aim of improving capability in the coming decade to quantify atmospheric CH4 budgets on the scales necessary for the success of climate policies.

Original languageEnglish
Pages (from-to)1475-1512
Number of pages38
JournalGlobal Biogeochemical Cycles
Volume33
Issue number12
DOIs
Publication statusPublished - 23 Dec 2019

Funding

We would like to thank those that strive to maintain long‐term records of atmospheric CH 4 around the world and those that perform the meticulous measurements that make CH 4 science possible. We thank Daniel Hoare for the high‐resolution U.K. CH 4 emissions map, and we thank Giuseppe Etiope and David Lyon for discussions. A. L. G was supported by U.K. Natural Environment Research Council (NERC) Independent Research Fellowship (NE/L010992/1). B. P. acknowledges support from the NASA Terrestrial Ecology Program. R. B. J and B. P. acknowledge support from the Gordon and Betty Moore Foundation (GBMF5439). A. G., M. R., and E. N. acknowledge funding from the NERC MOYA project (NE/N016548/1 and NE/N016211/1). S. P. acknowledges funding by the Dutch Technology Foundation STW of the Netherlands Organisation for Scientific Research (GALES, 15597). The generation of the SRON GOSAT and TROPOMI XCH : WMO/GAW World Data Centre for Greenhouse Gases ( : ESA TROPOMI Level 2 XCH 4 data shown here is funded by Copernicus Climate Change Service and ESA's Climate change initiative. Sentinel‐5 Precursor satellite is part of the EU Copernicus program, and the TROPOMI instrument is commissioned by Netherlands Space Office (NSO) and ESA. Data shown in Figure  https://gaw.kishou.go.jp ), NOAA GLOBALVIEWplus ( https://www.esrl.noaa.gov/gmd/ccgg/obspack/ ), NIES Center for Global Environmental Research ( http://db.cger.nies.go.jp/portal/geds/atmosphericAndOceanicMonitoring ), and NOAA AirCore ( ftp://aftp.cmdl.noaa.gov/data/AirCore ). Data shown in Figure  4 (version RPRO 1.2.0) ( https://doi.org/10.5270/S5P‐3p6lnwd ) and ESA CCI GOSAT SRPR XCH 4 version 2.3.8 ( ftp://ftp.sron.nl/pub/pub/RemoTeC/C3S/CH4_GOS_SRPR/ ).

FundersFunder number
GALES15597
NERC MOYA
NIES Center for Global Environmental Research
NOAA AirCorepub/pub/RemoTeC/C3S/CH4_GOS_SRPR/
NOAA GLOBALVIEWplus
National Aeronautics and Space Administration
Gordon and Betty Moore FoundationGBMF5439
Natural Environment Research CouncilNE/N016548/1, NE/N016211/1, NE/L010992/1
European Commission
European Space Agency
Netherlands Space Office
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Stichting voor de Technische Wetenschappen

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