Quantifying methane emissions in remote tropical settings: a new 3D approach

The purpose of this proposal is to develop a viable methodology to quantify methane emissions in remote seasonal tropical wetland settings in Africa, and thus to place constraints on the causes of growth. The NERC/Met Office FAAM aircraft is scheduled to be deployed to Uganda in early 2019: this proposal builds on the opportunity that deployment offers, by adding a detachment to the major seasonal southern tropical wetlands in Zambia's Congo and Zambesi river drainages.

Atmospheric methane began rising rapidly in 2007, after a period of stability, and the growth rate then accelerated in 2014 and subsequent years. Concurrently with the rise, the methane burden has shown a marked isotopic shift, becoming more C-13 depleted. We do not know why the methane growth and isotopic shift is happening. Much of the growth since 2007 has been in the tropics, and sub-tropics. One hypothesis for the growth and isotopic shift in the methane burden is that methane emissions from tropical wetlands and cattle are rapidly increasing, as a response to the tropical expansion and increased precipitation that has accompanied meteorological warming. An alternative hypothesis is that a marked decline in OH, the main sink, has lengthened methane's lifetime. Thus determining the flux and isotopic signatures of methane emissions from large representative seasonal African wetlands is a key requirement, enabling models to have better treatment of tropical latitudinal zones, so that the methane puzzle can be understood.

African tropical wetlands are dominated by C-13 rich C4 plants such as papyrus, and subsistence cattle also graze C4 plants. In comparison to temperate and cool climate sources, biogenic methane emitted to the air from African wetlands and cattle has a very different isotopic signature, richer in 13C. This isotopic signature of methane from African wetlands overlaps somewhat with some fossil fuel emissions. To use isotopes effectively to differentiate between source types in the global budget (e.g. fossil fuels or wetlands and cattle) it is urgent that much better information is obtained on the regional isotopic signatures of African biogenic emissions.

Methane growth since 2007 has been so rapid that methane is already far from its expected pathway under the UN Paris Agreement on Climate Change. There is a large discrepancy between reported national emissions inventories and atmsopheric estimates: in particular there is an urgent need for better tropical inventories if the budget is to be understood.

To address these problems, we intend:
1. To conduct a FAAM (Facility for Airborne Atmospheric Measurement) field deployment over Zambian wetlands, as a southern 'add-on' to our planned MOYA deployment to Uganda in January 2019, to measure wet-season greenhouse gas fluxes from the very extensive Zambian wetlands and farming areas around Lakes Bangweulu and Mweru, and in the Kafue and Zambesi basins. Flights would be carried out downwind of major wetland source regions, quantifying emission plumes at the height of the wet season.
2. To help solve the 'are emissions rising or is the OH sink falling?' debate, on-ground campaigns will be used to determine d13C[CH4] and dD[CH4] isotopic signatures, measured in emissions from Zambian C4 wetlands. The lack of measurement of isotopic signatures of tropical emissions is a crucial impediment to successful global inverse modelling (Turner et al., 2017; Rigby et al., 2017).
3. To develop low-cost ways of quantifying emission fluxes and determining isotopic signatures from major sources in remote tropical settings, including wetlands, cattle and biomass burning. In particular, a simple drone (UAV) and balloon bag-sampling methodology will be tested.
4. To improve 'bottom-up' assessment of local emission inventors, working with local colleagues in Zambia and Zimbabwe to construct national methane emission inventories, and thus support the intentions of the Paris Agreement.

The 2015 UN FCCC Paris Agreement to limit anthropogenic climate warming to below 2o C is failing because of the methane rise, despite efforts to reduce CO2 emissions. The main impact of this project will be to help quantify what measures are needed to put the Paris process back on track. By identifying what is driving the methane rise, quantifying it, and improving prediction of future change, the work will help set stronger targets for emission reduction in controllable sources such as fossil fuels and landfills.

1. Scientific Publication. This work has major scientific impact, far outside the small methane community, and reaching into the policy-setting domain. We have a very strong record of publication and dissemination. RHUL leads the MOYA Global Methane Budget team. Four recent papers are designated 'highly cited' by Web of Science. We have a sustained record of invited comment in Science Perspectives and Nature News and Views.
Delivery milestones: It is intended publication will continue at a high rate. The group's past projects have led to many papers per project: this will be the same.

2. Meetings. We led the 'Union' session on Methane at the 2013 AGU, and the Royal Society's 2010 Discussion meeting on Greenhouse gases. In 2017, the RHUL methane team led major Methane sessions at the European Geoscience Union. This will continue, with a proposal for a Royal Soc. discussion meeting and major symposia at AGU 2018. The MOYA blog regularly updates on our work:
http://moya.blogs.bris.ac.uk/
Delivery milestones: AGU and EGU presentations within 12 months. Royal Society Discussion Meeting proposal.

2. Media dissemination. There is very strong media interest in this work. Nisbet et al. (2016) was very widely disseminated by Reuters, with a long, accurate and detailed report, and also by most mainstream UK newspapers (including a surprisingly accurate report in the Daily Mail, and the Daily Express, wildly inaccurate). There is much interest from media worldwide, especially the US. The South China Morning Post, East Asia's main English language paper, ran a major magazine article on our work. Nov. 2017, interview with The Economist. The late 2017 documentary on BBC Radio "Discovery: Cheating The Atmosphere" includes much of our work http://www.bbc.co.uk/programmes/w3csvpfz.
Delivery milestones: Continuing media links tied to scientific publications. Team members are in regular close contact with print and broadcast media.

3. Corporate Impact. A recent estimate by Shindell et al (Faraday Disc. 2017) of the 'social cost' of methane emissions found, with typical discount rates, that methane costs lay in the range US$2400 - $3600 per ton, or 50-100 times the parallel cost of not emitting CO2. By developing a methodology for routine 3D mapping of emissions in tropical sites, and then using the flux quantification to direct attention on reduction measures - for example from neglected tropical landfills, a rapidly increasing source in developing nations - and also from biomass burning, the work will provide methods for tropical nations to quantify, locate, and hence target efforts to reduce their own local 'tractable' emissions.
Delivery milestones: team partners in Zimbabwe and Zambia have long-standing links with environmental management companies and farmers: these links and media reports can be used to enhance corporate awareness.

4. Public Policy. Better emissions inventories for Zambia and and Zimbabwe will assist the Paris Agreement. Nisbet has been invited to Nigeria, in early 2018, to brief ministries of environment and oil on methane emissions. Paris is now a central underpinning of UK energy and environmental strategic planning, and a core part of UK foreign policy. The unexpected recent methane rise, not appreciated at the time of the Paris undertaking, presents a severe challenge to the success of the UK's future climate change plans.
Delivery: ongoing briefings, UK and Africa.