Evidence for an Unexpectedly Large Greenhouse Gas Impact From Natural Gas Extraction

Scot Miller, Harvard University

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Methane accounts for an important share of greenhouse gas emissions in the United States, but estimates of total methane sources over North America vary by over 50 percent, a margin inadequate for policy decisions on future greenhouse gas reductions. We analyze observed concentrations of atmospheric methane over North America in order to resolve discrepancies in published assessments of methane emissions. We combine a comprehensive suite of atmospheric measurements, a high-resolution atmospheric transport model, and diverse spatial datasets to provide maps of anthropogenic methane sources in the United States. The results show large methane sources over Texas, Oklahoma, and Louisiana, the major locus of oil refining and natural gas extraction in the continental United States. Correlations of measured methane and propane concentrations in this region confirm a fossil fuel extraction source. Methane from these three states alone accounts for about 25 percent of total U.S. emissions, and the magnitude of emissions from the fossil fuel extraction and/or refining sector appears to have been significantly underestimated by most assessments. Here we show that natural gas extraction and processing likely has a much larger greenhouse gas footprint than commonly estimated.

Abstract Author(s): Scot M. Miller, Steven C. Wofsy, Anna M. Michalak, Eric A. Kort, Arlyn E. Andrews, Sebastien C. Biraud, Ed. J. Dlugokencky, Marc L. Fischer, G. Janssens-Maenhout , Ben R. Miller, Stephen A. Montzka, and Colm Sweeney