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Atmospheric methane (CH4) is a strong climate factor, responsible for a third of the increase in global temperature since the pre-industrial era (1). It has a much shorter lifespan than carbon dioxide (CO2) and 80 times the warming potential over a 20-year horizon. Mitigating methane emissions is critical to limiting global warming to 1.5°C and also has co-benefits for public health and food productivity (2Methane has a range of sources, including wetlands as a major natural producer and agriculture (livestock, rice), waste (landfills, wastewater) and the use of fossil fuels (coal, oil, gas) as major anthropogenic producers of emissions (3). Mitigating methane emissions from the oil/gas industry is of particular interest due to its high feasibility and economic benefits.
The United States is the world's leading producer of oil/gas methane, with national emissions of 8.1 Tg, according to reports from the United Nations Framework Convention on Climate Change (UNFCCC).-1 This represents 15 % of global methane emissions from oil/gas in 2019 (9). Oil and natural gas production in the United States increased by 137% from 2005 to 2019 (137% from 2005 to 2019).10, 11The U.S. Environmental Protection Agency (EPA) reports no significant change in its inventory of methane emissions over the period, reflecting improved industrial practices and the capture of associated gas to offset rising oil production (12However, top-down estimates from atmospheric methane observations suggest 0.4 to 6%-1 increase in methane emissions from oil/gas in the US between 2006 and 2017 (13 – 17) and national emissions about twice as high as reported by the EPA (5, 15, 16, 18, 19). Insufficient evidence of anomalously large sources (so-called superemitters) has been blamed for underestimating at least part of the reserves (5, 20, 21), but there are few studies on the factors that influence the long-term emission trend. (Xiao Lu)
