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Methane emissions show recent decline but strong seasonality in two US Northeastern cities



Anna Karion, Subhomoy Ghosh, Israel Lopez Coto, Kimberly Mueller, Sharon Gourdji, Joseph Pitt, James Whetstone


Urban methane emissions have been found to exceed estimates derived using traditional inventory methods in several US cities. In large northeastern US cities, including in Washington, DC and Baltimore, Maryland, studies using atmospheric methane observations to estimate emissions have suggested that natural gas losses are the dominant source of discrepancies between atmospheric and traditional inventory methods. In this work, we have leveraged a nearly five-year record of observations from a dense tower network coupled with a newly developed high-resolution emissions map in these two urban areas to quantify emission rates. We find a decreasing trend in methane emissions of approximately 4 % to 5 % per year between 2018 and 2021. We find higher wintertime emissions correlating with natural gas consumption and attribute a large fraction of total methane emissions to the natural gas sector using a least squares regression on our estimates. Our analysis supports previous findings that natural gas systems emit the plurality of methane in both cities. This study contributes to the relatively sparse existing knowledge base of urban methane emissions sources and variability, adding to our understanding of how these emissions change in time, and provides evidence to support efforts to mitigate natural gas emissions.
Environmental Science & Technology


methane, natural gas, greenhouse gas, urban


Karion, A. , Ghosh, S. , Lopez Coto, I. , Mueller, K. , Gourdji, S. , Pitt, J. and Whetstone, J. (2023), Methane emissions show recent decline but strong seasonality in two US Northeastern cities, Environmental Science & Technology, [online], (Accessed July 21, 2024)


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Created November 9, 2023, Updated January 12, 2024