Discovering reasons for global atmospheric methane growth using deuterium isotopes

Lead Research Organisation: Royal Holloway University of London
Department Name: Earth Sciences

Abstract

This proposal is to measure and model deuterium/hydrogen (D/H) isotope ratios in methane, to constrain the uncertainties in the global methane budget. Measurement will include 1) Field campaigns to determine isotopic source signatures; 2) time series from remote stations in both hemispheres; and 3) modelling to extract global budgets and causes of change.

Atmospheric methane is growing rapidly. Its mixing ratio has risen 80 ppb (over 4% of total burden) since 2007. Growth accelerated in 2014 (13 ppb/yr) and has continued to be high since (7 to 10 ppb/yr). This high methane growth was unexpected and presents one of the greatest immediate challenges to the Paris Agreement. The reasons behind renewed methane growth since 2007 and acceleration in 2014 are not understood. Was it caused by increased emissions, and if so from which sources, or by declining OH, the main sink of methane? Is growth a feedback from climate change, the warming feeding warming? Or is it a direct consequence of human activities?

Mixing ratio measurements alone are inadequate to solve the methane budget, though geographic foci indicate the main driving factors are in the tropics and low northern latitudes. Isotopologues (variations in the relative amounts of 12CH4, 13CH4 and 12CH3D) identify and discriminate between source and sink changes. After two centuries of becoming more 13C-rich, methane has shifted 'light' (more 12C-rich) since 2007. The C-isotope change gives insight into the main driving factors behind growth, but more information is needed to fully understand the reasons for interannual variability and continued methane growth. The greatest need is to measure H-isotopes, which provide extremely powerful discriminants of methane sources and sinks.

A new technical advance in measuring H-isotopes in methane in ambient air permits this project. A new rapid multiple-sample high-precision mass spectrometric system, which radically cuts the per-sample cost of measurement was installed in late 2019 and was a major goal of NERC's MOYA highlight project. It will allow thousands of ambient air samples per year to be analysed for H-isotopes.

Currently only very few labs worldwide make this challenging measurement and source isotopic signatures and time series of ambient air measurements are sparse. The new work will reinstate a global two-hemisphere network, measuring time series in the Arctic, northern mid-latitudes, tropics, southern mid-latitudes, and Antarctica.

D/H isotopic signatures of the major sources will be characterised: wetlands, waste, biomass burning, fossil fuel, ruminants and rice agriculture. Field campaigns will focus on tropical Africa, East Asia and S America, with high emissions of methane, but very few measurements of methane isotopic signatures. Results will give regional source signatures for the source types.

Modelling will use the new measurements and source signatures to constrain the global methane budget. Combining time series measurements of methane mole fraction and 13C/12C and D/H in methane with improved source signatures will determine latitudinal gradients and temporal trends, Numerical modelling using the UM-UKCA chemical transport model will use D/H as a key discriminant, to test the various hypotheses and identify the causes of methane's rise.

The new rapid multi-sample system, which permits us to go from studying methane in 2D (mixing ratio + C-isotopes) to 3D (adding H-isotopes), is a radical advance in solving the methane budget problem. Understanding why methane is rising is critical to driving mitigation policy to attain the Paris Agreement's goals. This project will lead to a major improvement in understanding the global methane budget, and help shape decisions on strategies needed to stabilise and reduce methane.

Planned Impact

By adding the D/H dimension to methane study and our consequent improved understanding of the global methane budget, this project will have far-reaching scientific impact, and from that will come powerful impact on public policy.

1. Improvements will be made to the UK and global methane emissions inventories through this work allowing better targeting of sources to focus on for greenhouse gas reduction policies. In the UK, US and Europe, there will be direct feed-in to government policy framers and decision makers. In the UK, the Consortium team will advise policymakers in the BEIS department. The PI and Co-Is have since the 1990s participated for the UK in what was formerly the UN/WMO/IAEA "Expert" panel, now called UN GGMT, linked to the UN Global Atmosphere Watch and this offers a channel for dissemination of results to global policy makers.

2. Industrial impact will be strong. The methane D/H analysis system was designed and built in the UK in close collaboration with RHUL, and successful use will expand its market, and hence the amount of data available in the future for modelling studies. More generally, better source identification and flux determination of methane sources that will come from using D/H data will strongly help mitigation efforts by major energy companies, helping them to find and cut gas leaks and other industrial emissions. This is a very high priority for all major gas industry players and for waste management companies.

3. For the general public, the media interest in the rapidly changing methane budget is very powerful. As examples, the 2016 and 2019 synthesis papers from NERC's MOYA consortium were very widely reported in the international print and broadcast media, with the highest 'Altmetrics' (media impact) score ever achieved by a paper in the journal (Global Biogeochemical Cycles). Feature reports were in the UK (in major papers and BBC, Nature, Economist) and also worldwide (e.g. LA Times, Science). We expect similar high impact from the publications that will come out of this proposal.

4. For educational impact the results of this project will be used as a teaching tool, with a website designed to educate the public on methane's role in climate change, and an interactive map and blogs of field campaigns. We will publicise results in local schools and colleges and run workshops at RHUL and at the host institutions of the Bolivia and Vietnam field campaigns. The field campaigns will promote a greater awareness of the role of methane in climate change, what the sources are, and importantly where reduction of emissions is possible.

The primary impact will be to help the Paris Agreement. This is amongst the most important of all international treaties. We must find out why methane is rising; we must find ways to counter the rise. D/H measurement is essential if we are to achieve this, to understand and ultimately reduce atmospheric methane levels.

Publications

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France JL (2022) d13C methane source signatures from tropical wetland and rice field emissions. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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France JL (2022) Very large fluxes of methane measured above Bolivian seasonal wetlands. in Proceedings of the National Academy of Sciences of the United States of America

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Lan X (2021) What do we know about the global methane budget? Results from four decades of atmospheric CH4 observations and the way forward. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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MOYA/ZWAMPS Team (2022) Isotopic signatures of methane emissions from tropical fires, agriculture and wetlands: the MOYA and ZWAMPS flights. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Nisbet EG (2021) Atmospheric methane and nitrous oxide: challenges alongthe path to Net Zero. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Nisbet EG (2021) Rising methane: is warming feeding warming? in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Nisbet EG (2022) The urgent need to cut methane emissions. in National science review

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Nisbet EG (2022) Rising methane: is there a methane emergency? in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

 
Description International Methane Emissions Observatory
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a guidance/advisory committee
Impact The impact is ongoing - improved understanding of the opportunities for methane mitigation to support the Global Methane Pledge.
URL https://www.unep.org/resources/report/eye-methane-international-methane-emissions-observatory-2022-r...
 
Description Member: Science Advisory Panel, UN International Methane Emissions Observatory (specified commitment in the UN Global Methane Pledge)
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a guidance/advisory committee
Impact UN IMEO supports a series of experimental studies, especially with aircraft, to locate and quantify major sources of methane emisisons, especially from the energy industry.
URL https://www.unep.org/explore-topics/energy/what-we-do/imeo
 
Description International Methane Emissions Observatory 
Organisation United Nations (UN)
Department United Nations Environment Programme
Country Kenya 
Sector Charity/Non Profit 
PI Contribution Dr. James France acts as Science Advisor to IMEO's Methane Science Studies Programme. Prof Euan Nisbet is an advisory board member.
Collaborator Contribution Development of links to global network of researchers measuring methane
Impact An Eye on Methane: International Methane Emissions Observatory 2022 Report (Roland Kupers, Daniel Zavala-Araiza, Giulia Ferrini, Stefan Schwietzke, Erin Tullos, Cynthia Randles, James France, Luis Guanter, Manfredi Caltagirone, Meghan Demeter and Marci Baranski), UNEP, 2022. Multidisciplinary - science and policy
Start Year 2022
 
Description COP26 Innovation Showcase Panel Meeting: 'What role does measurement play in climate action?' 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This was an online event which was run during the COP26 conference. Methods for using measurements to quantify methane emissions were presented by PhD students, followed by a panel discussion. Mobile greenhouse gas measurements using the MIGGAS equipment were demonstrated. Over 80 delegates attended and Mentimeter was used to gain audience feedback showing an increased understanding of the role that measurements play in quantifying greenhouse gas emissions.
Year(s) Of Engagement Activity 2021
 
Description Financial Times 'Big Read': Methane hunters: what explains the surge in the potent greenhouse gas? Aug 23, 2022 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Interview and discussions with Financial Times climate team - FT 'Big Read'
Year(s) Of Engagement Activity 2022
URL https://www.ft.com/content/9ef195d6-dcc3-4378-bb35-2721981d6416
 
Description Financial Times newspaper article 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Collaboration and interview with the Financial Times to report mobile methane measurements in Glasgow. The web version of the article included an illustration of measurements used using the MIGGAS equipment. Led to a front page article 'Methane leak near COP26 venue underscores emissions challenge' on 23rd October 2021 (8 days before the start of COP26). The purpose was to highlight the types of methane sources that are present in cities and are cost effective to reduce, and the ability of mobile instrumentation to detect these. There was a great deal of interest in this work at COP26, especially as it links closely to the Global Methane Pledge.
Year(s) Of Engagement Activity 2021
URL https://www.ft.com/content/c9c43e4f-c83e-42e4-a815-9266b970af7a
 
Description ITV Jersey intervew 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact ITV Jersey interview with Royal Holloway and Jersey Dairy farmers to explain the mobile measurements being made around farms, to explain the sources of methane emissions in Jersey, how they can be measured, and opportunities to reduce emissions. The recording was broadcast on the TV news and online ' Jersey pioneers testing new methane measuring technology' (18th November 2021).
Year(s) Of Engagement Activity 2021
URL https://www.itv.com/news/channel/2021-11-18/jersey-pioneers-testing-new-methane-measuring-technology
 
Description Interview for Times Radio 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview with Rebecca Fisher from COP26 (Times Radio, interviewed by Mariella Frostrup) following the announcement of the Global Methane Pledge at COP26. Explained the science behind the Global methane pledge, and where emissions can most easily be cut.
Year(s) Of Engagement Activity 2021
 
Description Invited Keynote talk: Has Termination Zero begun? - the urgent need to monitor methane isotopes. UN WMO International Greenhouse Gas Monitoring Symposium at WMO in Geneva, Switzerland, 30 January -1 February 2023. 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Invited talk to major international workshop on greennhouse gas measurement, with senior level participation from UN, US, EU, etc etc.
Year(s) Of Engagement Activity 2023
URL https://community.wmo.int/en/meetings/wmo-international-greenhouse-gas-monitoring-symposium
 
Description Participation at COP26 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Rebecca Fisher attended COP26 as an observer. Participated in 1-to-1 and small group discussions on the Global methane pledge, and how mobile and isotopic measurements can be used to identify sources that can be reduced.
Year(s) Of Engagement Activity 2021
 
Description Radio Interviews for LBC News 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Two interviews with Rebecca Fisher, discussing methane mitigation opportunities and COP27
Year(s) Of Engagement Activity 2022