Urban Natural Gas Seasonality is Associated with Commercial Areas in Berkeley, California

Recent measurement studies have found that urban natural gas (NG) emissions are 3.9× larger than bottom-up inventory estimates, on average, across various North American cities.1 Several studies have proposed that post-meter emissions may be a substantial missing source in urban methane (CH4) estimates, but the role of diffuse residential and commercial NG consumption in overall emissions remains uncertain. Long-term, continuous eddy covariance flux measurements can help clarify possible post-meter contributions by providing localized, high-resolution observations of cumulative emissions. Here we present nearly 3 years of CH4 flux measurements collected between July, 2022 and April, 2025 from a 42 m tall stationary tower located in downtown Berkeley, California, USA. Methane source types were characterized using contemporaneous ethane and δ13CH4 measurements, and spatially resolved population, building, and land use datasets were used to determine possible post-meter emissions drivers. Average annual CH4 fluxes in Berkeley were 152 nmol m-2 s-1 [95%: 150,155] and were primarily attributed to natural gas. Fluxes were dominated by a persistent spatial gradient wherein higher fluxes were associated with increased commercial building space and lower population density in the downtown core, with estimated average annual fluxes ranging from 85 nmol m-2 s-1 [95%: 82.8, 88.3] in residential areas to 218 nmol m-2 s-1 [95%: 214, 223] downtown. Flux diurnal trends were distinct between different seasons and dominant land uses, but no significant weekday-weekend differences were observed. Residential areas had lower diurnal variation and higher springtime fluxes—exhibiting no positive correlation with NG consumption. In denser commercial areas, CH4 fluxes were significantly lower during warmer months, and monthly emissions were positively correlated with NG consumption at rates of 0.21% and 0.23%. Overall fluxes were 5× larger than the highest inventory estimates and were elevated relative to urban eddy covariance studies in similarly sized European and Asian cities. Our results emphasize how eddy covariance studies can help identify and track the drivers of larger urban CH4 emissions trends and the importance of evaluating these trends across different spatial scales.[1] Vollrath, et al. (2025) Environ. Res. Lett.