UK analysis of data from the Japanese GOSAT satellite over many years is revealing detailed regional patterns in methane emissions. Predictions of future climate change need to understand and model global distributions of greenhouse gases, and the different processes that control their behaviour.
Methane (CH4) is a powerful greenhouse gas that is produced by a variety of natural and industrial processes. It is 86 times stronger as a greenhouse gas than carbon dioxide. It is increasing in the atmosphere due to human activity and is an important contributor to global warming.
Methane is emitted from a variety of sources, from both the natural environment and through human activity. The main sources of atmospheric methane are natural wetlands, rice cultivation, fossil fuel production, livestock and biomass burning.
There has been a steady increase in methane up to the end of the 1990s followed by a period of stagnation in the early 2000s and another increase since the late 2000s. Our current understanding of methane sources and sink is insufficient to explain this behaviour.
One reason for our limited understanding of the methane budget is that the ground-based measurement network cannot capture methane sources sufficiently well, especially in remote regions. Satellites are helping to overcome this limitation and we now have more than a decade of global methane observations from satellites which has already led to a number of new insights into the methane budget.
Predictions of future climate change need to understand and model global distributions of greenhouse gases, and the different processes that control their behaviour. Methane does not persist in the atmosphere for a long time like carbon dioxide, but it is important to know how much of it is present, and where it enters the atmosphere.
Application
Global atmospheric methane levels are now more than double the pre-industrial levels. Despite the huge growth in methane emissions after the industrial revolution, the growth rate had been steadily declining over the last three decades, dropping to almost no annual growth in the early 2000s. This lack of growth suggested a change in the balance between the various sources and sinks. However, there has been sudden, and unexpected, renewed growth in atmospheric methane levels from 2007. This has highlighted significant gaps in our current knowledge.
Methane can be observed by two types of satellite instrument. Instruments such as GOSAT and TROPOMI use surface-reflected sunlight in the shortwave-infrared spectral region. This allows information to be collected on the total column of methane in the atmosphere. Measurements in the thermal-infrared range are made by instruments such as IASI. These observations have their peak sensitivity in the free troposphere and they have the advantage that they do not rely on sunlight and thus provide information over ocean as well as land and during Arctic winter.
GOSAT
Launched on 23 January, 2009, the Greenhouse gases Observing SATellite (GOSAT) is the world’s first spacecraft to measure the concentrations of carbon dioxide and methane from space.
UK analysis of data from the Japanese GOSAT satellite over many years is revealing detailed regional patterns in methane emissions. The visualisation below shows methane amount derived by scientists at the University of Leicester – NCEO from GOSAT satellite data.
The high methane values over Asia in autumn are indicative of emissions from rice growing and wetlands, whilst those over Africa and Indonesia are related to biomass burning and wetland emissions.
Measurements from GOSAT are optimised for the characterisation of continental-scale sources and sinks with the aim of achieving an accuracy of better than 2% for 3-month averages of methane at a 100-1000~km spatial resolution. The GOSAT satellite measures atmospheric spectra of reflected sunlight that allow us to infer the amount of methane in the atmosphere.
Investigations will continue with the recently launched European Sentinel 5P satellite which provides data at much improved spatial resolution.
IASI
Scientists at RAL Space have developed a multi-year dataset using measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on board EUMETSAT’s MetOp satellite. Find out more about that dataset heree: RAL Space Case study: Satellite data show methane increase at all latitudes (opens in new tab)
IASI provides coverage every 12 hours, day and night, at all latitudes in all seasons. This complements data-sets produced from short-wave satellite measurements by other National Centre for Earth Observation (NCEO) and European groups.
The IASI measurements from MetOp are currently providing a continuous, stable methane data record which commenced in 2007 and is due to be extended by MetOp Second Generation for a further two decades. The scheme resolves two vertical layers of methane to help differentiate changes occurring lower in the troposphere from those occurring higher in the troposphere and stratosphere above.
The dataset featured in the video shows tropospheric methane to be increasing at all latitudes including the Arctic (see below). Analysis should help establish the causes of increase in different regions e.g. whether the Arctic increase is entirely due to transport of methane from lower latitude sources (wetlands, wildfires, agriculture, industry) or possibly also to thawing permafrost. This could improve our understanding of the relationships between methane and climate change.
Multi-year dataset using measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on board EUMETSAT’s MetOp satellite. This dataset shows tropospheric methane to be increasing at all latitudes including the Arctic. Source: NCEO RAL Space
UK Expertise
Professor Hartmut Boesch is a National Centre for Earth Observation (NCEO) Division Director and Professor at the University of Leicester. He is an expert in satellite remote sensing, researching on greenhouse gases and solar-induced fluorescence. Previously he worked for several years at the NASA Jet Propulsion Laboratory on the development of the NASA Orbiting Carbon Observatory (OCO) mission. He is a science team member of the NASA OCO-2 and CNES Microcarb missions.
Dr Robert Parker is a NCEO scientist and an expert in satellite retrievals of greenhouse gases with more than 10 years of experience. He was awarded an ESA Living Planet Research Fellow with a focus on interpreting and exploiting satellite data to better understanding the global carbon cycle and the associated surface fluxes.
The RAL Space remote sensing group is one of the partners of NCEO. The following scientists within it have expertise in methane retrieval:
Dr Richard Siddans – Expert in retrieval of methane and other trace gases from satellite observations and member of ESA’s Mission Advisory Group for Sentinels 4 &5
Dr Diane Knappett – NCEO scientist specialising in methane retrieval with ESA Living Planet Fellowship on combining thermal infrared and shortwave infrared observations
Dr Brian Kerridge – Leader, RAL Remote-Sensing Group with extensive experience in satellite sounding of atmospheric composition
Climate EO data supply chain
- Japanese GOSAT satellite: University of Leicester thanks the Japanese Aerospace Exploration Agency, National Institute for Environmental Studies, and the Ministry of Environment for the GOSAT L1B data and their continuous support as part of the Joint Research Agreement;
- Level-1 data from IASI on the MetOp satellites are provided by Eumetsat and processed on Jasmin.
- Data processing: The processed datasets were generated as part of the European Space Agency’s Climate Change Initiative, ESA GHG-CCI (http://www.esa-ghg-cci.org/) and Copernicus Climate Change Service (C3S) ( https://climate.copernicus.eu/) and will be available on the C3S Data Store. They are also available directly from University of Leicester (contact rjp23@le.ac.uk for details).
- Examples of scientific publications:
- Siddans, R.; Knappett, D.; Kerridge, B.; Latter, B.; Waterfall, A. (2020): STFC RAL methane retrievals from IASI on board MetOp-A, version 2.0. Centre for Environmental Data Analysis, 10 March 2020. doi:10.5285/f717a8ea622f495397f4e76f777349d1. http://dx.doi.org/10.5285/f717a8ea622f495397f4e76f777349d1
- Ganesan et al., 2017, Nature Communications, 8, 836, doi:10.1038/s41467-017-00994-7
- Siddans, R., Knappett, D., Kerridge, B., Waterfall, A., Hurley, J., Latter, B., Boesch, H., and Parker, R.: Global height-resolved methane retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp, Atmos. Meas. Tech., 10, 4135–4164, https://doi.org/10.5194/amt-10-4135-2017 , 2017.
- Parker, R., et al., 2011, Methane observations from the Greenhouse Gases Observing SATellite: Comparison to ground‐based TCCON data and model calculations, Geophys. Res. Lett., 38, L15807, doi:10.1029/2011GL047871
- Parker, R. J., et al, Assessing 5 years of GOSAT Proxy XCH4 data and associated uncertainties, Atmos. Meas. Tech., 8, 4785-4801, https://doi.org/10.5194/amt-8-4785-2015, 2015
- Parker, R. J. et al., 2016, Atmospheric CH4 and CO2enhancements and biomass burning emission ratios derived from satellite observations of the 2015 https://doi.org/10.5194/amt-8-4785-2015 Indonesian fire plumes, Atmos. Chem. Phys., 16, 10111-10131, https://doi.org/10.5194/acp-16-10111-2016, 2016
- Parker, R. J., et al., Evaluating year-to-year anomalies in tropical wetland methane emissions using satellite CH4 observations, Remote Sensing of Environment, 211, 261-275, 2018, https://doi.org/10.1016/j.rse.2018.02.011, 2018
Future missions
Advancing mission technology for localised sources of methane emissions
It would be a quick win for our climate if we could identify and eliminate emissions from the coal, gas and oil industries, and other localised sources.
Infrared sensors on satellites help us to identify gases in the atmosphere, including the greenhouse gas Methane. Existing instruments and missions show broadly where, and how much, methane is present, but each data value (pixel) represents 7-10km. With this spatial resolution, it is not possible to precisely identify sources of emission. To identify an industrial source, ground resolution of better than 100 metres is required.
The UK Centre for Earth Observation and Instrumentation (CEOI) is a partnership formed from four of the major space organisations in the UK, namely Airbus Defence and Space, the University of Leicester, QinetiQ, and STFC RAL Space. The CEOI has been charged by the UK Space Agency to assist national institutes, academia and companies to develop and prepare novel and powerful instrumentation for flight on the next generation of Earth observation satellites.
CEOI and UKSA have been supporting some key technologies that can make the next generation of methane monitoring satellites possible:
- New high-resolution infrared detector technology.
- Miniature instrumentation and deployable optics so that small, low-cost modular satellites (CubeSats) can be used.
- Novel methane-specific narrow-band filter spectrometer design.
- Constellation deployment, allowing many locations to be imaged daily
NIMCAM is a new UK-led mission under development at the University of Edinburgh, supported by CEOI and UKSA.
- Suitable for deployment in a small modular satellite known as a CubeSat.
- Ground sampling distance is 60 metres, and has a 30 km field of view.
- Will image methane release plumes on the ground from industrial sites.
Find out more here: NIMCAM_one_sider