This paper explores the science of measuring methane emissions and calls on the EPA to improve its approach to estimating methane emissions. New research concludes that methane emissions are significantly undercounted by the EPA Inventory of Greenhouse Gas Emissions and Sinks. Uncertainty remains about the sources of this “missing,” methane, but there are strong indications that at least some of it is coming from the natural gas system. Better data on methane emissions is needed to guide climate policy and more efficiently regulate the natural gas industry.