| Summary: | Reducing carbon dioxide (CO _2 ) emissions through a reliance on natural gas can create a hidden commitment to methane (CH _4 ) leakage mitigation. While the quantity of CH _4 leakage from natural gas has been studied extensively, the magnitude and timing of the CH _4 mitigation required to meet climate policy goals is less well understood. Here we address this topic by examining the case of US electricity under a range of baseline natural gas leakage rate estimates and emissions equivalency metrics for converting CH _4 to CO _2 -equivalent emissions. We find that CH _4 emissions from the power sector would need to be reduced by 30%–90% from today’s levels by 2030 in order to meet a CO _2 -equivalent climate policy target while continuing to rely on natural gas. These CH _4 emissions reductions are greater than the required CO _2 reductions under the same policy. Alternatively, expanding carbon-free sources more rapidly could meet the 2030 target without reductions in natural gas leakage rates. The results provide insight on an important policy choice in regions and sectors using natural gas, between emphasizing a natural gas supply chain clean-up effort or an accelerated transition toward carbon-free energy sources.
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