posted on 2023-11-09, 08:05authored byAnna Karion, Subhomoy Ghosh, Israel Lopez-Coto, Kimberly Mueller, Sharon Gourdji, Joseph Pitt, James Whetstone
Urban methane emissions
estimated using atmospheric observations
have been found to exceed estimates derived by using traditional inventory
methods in several northeastern US cities. In this work, we leveraged
a nearly five-year record of observations from a dense tower network
coupled with a newly developed high-resolution emissions map to quantify
methane emission rates in Washington, DC, and Baltimore, Maryland.
Annual emissions averaged over 2018–2021 were 80.1 [95% CI:
61.2, 98.9] Gg in the Washington, DC urban area and 47.4 [95% CI:
35.9, 58.5] Gg in the Baltimore urban area, with a decreasing trend
of approximately 4–5% per year in both cities. We also find
wintertime emissions 44% higher than summertime emissions, correlating
with natural gas consumption. We further attribute a large fraction
of total methane emissions to the natural gas sector using a least-squares
regression on our spatially resolved estimates, supporting 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 providing evidence to support efforts to mitigate natural gas
emissions.