Mapping of methane emissions from fossil fuel exploitation


The amount of methane in the Earth’s atmosphere has reached record levels in recent years. One of the main sources of emissions is the extraction, storage and transportation of oil, natural gas and coal, which releases about 97 million metric tons of methane every year, according to the United Nations. (UN). In a recent research project, scientists mapped where these emissions are coming from, not just by country, but within them.

Methane is a potent greenhouse gas, trapping about 35 times more heat than carbon dioxide. The United States aims to reduce methane emissions by 30% below 2020 levels by 2030, and other countries are making similar commitments.

Individual countries report their methane emissions by sector to the UN in accordance with the United Nations Framework Convention on Climate Change (UNFCCC). Most countries estimate their methane emissions using records of how much of each fossil fuel they produce each year, multiplied by an emission factor provided by the Intergovernmental Panel on Climate Change (IPCC ). And most governments only provide one figure for emissions from each sector (oil, coal, gas) across the country.

Funded by NASA’s Carbon Monitoring System, scientists recently constructed a new series of maps detailing the geography of methane emissions from fossil fuel production. Using publicly available data reported in 2016, the research team plotted fuel operating emissions – or “fugitive emissions” as the UNFCCC calls them – that occur before fuels are consumed. The maps show where these emissions are occurring based on the location of coal mines, oil and gas wells, pipelines, refineries, and fuel storage and transportation infrastructure. The maps were recently released to NASA’s Goddard Earth Sciences Data and Information Services Center (GES DISC). (Note that 2016 was the most recent year for which full United Nations emissions data was available at the time of this study.)

“It is well known that self-reported country estimates are not of the highest quality,” said Tia Scarpelli, leader of the effort and postdoctoral researcher at the University of Edinburgh. “Our maps provide researchers with a spatial representation of methane emissions so they can be compared to observations of methane concentrations from satellites.” These maps are essential for monitoring changes in greenhouse gas emissions because the data tells scientists where to look and where to expect most emissions.

The maps show that the largest sources of oil-related emissions are in Russia; the United States leads in natural gas emissions; and coal emissions are highest in China. For oil and gas, emissions are split between wells, flares, pipelines, refineries and storage facilities. For coal, emissions are mapped according to where it is mined.

Dark lines stand out on the map of natural gas emissions: they indicate the locations of gas pipelines. “Most emissions aren’t diffuse along pipelines,” said Scarpelli, who led the research as a graduate student at Harvard University. “They mostly come from compressor stations that are present every hundred miles or so along the pipelines to compress the gas and keep it moving.” In Canada, the aligned dots indicate the locations of compressor stations. But for Russia, Scarpelli and his colleagues had no reports of the locations of compressor stations or pipelines. They had to scan a paper map from the Harvard University library to map pipelines in Russia, then break down methane emissions based on the location of the pipelines.

By comparing the new inventory to methane observations from the Japan Aerospace Exploration Agency’s Greenhouse Gas Observation Satellite (GOSAT) and the European Space Agency’s Tropospheric Monitoring Instrument (TROPOMI) on Sentinel-5, Scarpelli’s colleagues at Harvard found that Canada and the United States tended to underestimate methane emissions from fossil fuels. But for coal in China and oil and gas in Russia, the inventory overestimated emissions. This could be due to uncertainties related to a lack of on the spot observations and precise data on the infrastructures.

NASA Earth Observatory images by Joshua Stevens, using data from the Global Inventory of Methane Emissions from Fuel Operations. Story by Emily Cassidy, NASA Earth Science Data Systems Program.


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