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Long‐Term Measurements Show Little Evidence for Large Increases in Total U.S. Methane Emissions Over the Past Decade
Author(s) -
Lan Xin,
Tans Pieter,
Sweeney Colm,
Andrews Arlyn,
Dlugokencky Edward,
Schwietzke Stefan,
Kofler Jonathan,
McKain Kathryn,
Thoning Kirk,
Crotwell Molly,
Montzka Stephen,
Miller Benjamin R.,
Biraud Sébastien C.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl081731
Subject(s) - greenhouse gas , methane , methane emissions , environmental science , atmospheric methane , atmospheric sciences , climatology , geology , oceanography , chemistry , organic chemistry
Recent studies show conflicting estimates of trends in methane (CH 4 ) emissions from oil and natural gas (ONG) operations in the United States. We analyze atmospheric CH 4 measurements from 20 North American sites in the National Oceanic and Atmospheric Administration Global Greenhouse Gas Reference Network and determined trends for 2006–2015. Using CH 4 vertical gradients as an indicator of regional surface emissions, we find no significant increase in emissions at most sites and modest increases at three sites heavily influenced by ONG activities. Our estimated increases in North American ONG CH 4 emissions (on average approximately 3.4 ± 1.4 %/year for 2006–2015, ±σ) are much smaller than estimates from some previous studies and below our detection threshold for total emissions increases at the east coast sites that are sensitive to U.S. outflows. We also find an increasing trend in ethane/methane emission ratios, which has resulted in major overestimation of oil and gas emissions trends in some previous studies.