While the studies indicated that natural gas is the dominant source of CH4 emissions from U.S. and Canadian cities, on average, they also revealed that the specific sources are not well understood. This makes it challenging to develop policies, regulations, and mitigation strategies with a precision approach. Three key findings from the review point to a research need to develop a better resolved understanding of specific sources and root causes of emissions from natural gas in cities. First, the average measurementderived CH4 loss rate for the urban areas studied (1.8% ± 0.9%) contradicts the O&G industry's claims of low-carbon differentiated gas, raising questions about industry estimation methods. The O&G industry cannot control CH4 leakage downstream of customer meters, but nontrivial slip emissions at the burner tip are consequential for estimates of the total supply chain CH4 intensity of natural gas and the climate. Second, analyses in the studies and our estimates based on the studies' emissions data point to end-use slip as a potential major contributor to urban CH4 emissions, but attributing the emissions to specific end uses (e.g., furnaces, boilers, appliances, gas turbines, and industrial processes) is impeded by a very limited number of emissions rate measurements. Third, despite numerous studies, the characterization of natural gas leaks from pipelines is largely speculative, because the attribution methods are imprecise. Research targeting these and related knowledge gaps has potential to inform mitigation and improve the climate performance of natural gas.