Evaluating Trends in Mobile CO2 Emissions Using a Near-Surface, High-Density Urban Monitoring Network

Urban areas comprise a large fraction of anthropogenic greenhouse gas emissions, and cities are implementing mitigation strategies to reduce emissions by sectors. However, observing and quantifying trends in an individual sector’s contribution to the overall urban emission is challenging as various emission sources are commingled within cities. To enhance, rather than average across or cancel out, our sensitivity to hyperlocal emission sources, we leverage near-surface, high-density urban observations from the Berkeley Environmental Air-quality & CO₂ Observation Network (BEACO₂N) in the San Francisco Bay Area. Here we demonstrate the Gaussian dispersion of mobile emissions from highways by combining the network of CO₂ measurements with traffic counts and show the inferred changes in vehicle fuel economy over the last few years. The ability to represent trends of policy-relevant magnitudes with high-density monitoring network has important implications for optimizing and evaluating greenhouse gas mitigations strategies.