Another problem with “natural” gas as a bridge is that much gas production in the US is now via hydraulic fracturing or “fracking,” which releases large amounts of methane into the atmosphere. Methane does not stay in the atmosphere as long as CO2, but it is 25 times more potent as a heat-trapping gas. Our current methane crisis appears to derived from fracked wells that have been left uncapped.

Source: It is now Cheaper to Switch from Coal directly to Wind and Solar than to Natural Gas