TD and BU approaches can be used to track and confirm reductions, but credibility in either is undermined by disagreement between estimates. We did not observe dedicated efforts at closing gaps between TD and BU estimates of city-level CH4 emissions in the studies. A general prerequisite to mitigating emissions is knowing individual source locations and rates, and the contribution of sources in aggregate to total city-level emissions. and developed geospatial BU inventories of CH4 emissions for Los Angeles and Toronto, respectively. These inventories include source locations and emissions estimates at a granular level, and as such may provide a starting point to resolve discrepancies between TD and BU estimates in cities. Field measurements of sources should be integrated into these inventories and rates updated over time. BU estimates that include empirical measurement data may have greater direct comparability to TD measurements, narrowing the discrepancy between the approaches observed at the city-level. Integrating measurement data into government BU inventories was recently shown to mostly address historic underestimation of emissions using the BU approach in the Canadian upstream oil and gas industry . Similar approaches can be adapted to improve and better constrain estimates of urban CH4 emissions in the U.S. and Canada.