Most people on earth live in cities and they are responsible for the majority of greenhouse gas emissions. Cities are also where exposure to poor air quality is most frequent and most variable. Understanding and managing the path to net-zero greenhouse gas emissions, improved public health and lower public health inequities requires a view into the emissions and atmospheric chemistry of cities with the fine grained detail that allows evaluation of specific processes and variations from one neighborhood to another. In this talk, I’ll describe recent progress in the analysis of observations from the Berkeley Environment, Air Quality and CO₂ Network (BEACO₂N http://beacon.berkeley.edu/about/), a dense network for mapping urban CO₂, NO_x, CO, O₃ and aerosol. Integration of the BEACO₂N maps with simple Gaussian plume models and sophisticated Bayesian inversions employing high resolution weather models provide unique observational constraints on spatial and temporal patterns of CO₂ and other emissions.