Methane is anywhere from 25 to 72 times as powerful an agent of global warming as CO2, depending on the given time horizon for the calculation (100 versus 25 years). When methane is burned (flared), CO2 results. But any unburned methane or methane leaking from wells, equipment, or pipelines, whether on purpose (vented) or otherwise (fugitive), contributes powerfully to global warming and leads to questions about whether natural gas is really a low-carbon fuel compared with coal or diesel.