Gas global warming potential:
This LNG report by Global Energy Monitor has a one-pager on this:
Depending on the assumptions about methane leakage rates, the relative efficiencies of the coal-fired and gas-fired power plants being compared, and the period over which warming is being measured, the global warming impact of building a new gas plant instead of a new coal plant, assuming the gas plant is supplied by LNG, can range from 29% lower to 16% higher
NRDC recently reported about methane leaks, to make the point: "Just because something is better than something else doesn’t necessarily make it good."
And here, Colorado State University scientists cite their own direct measurements of 700 gas chain facility methane leaks. The research suggests that fugitive methane emissions from US gas operations are 60% higher than US EPA estimates. (I think these are the same findings reported by Environmental Defense Fund and Desmog)
…we find the total methane emission from the well blowout is comparable to one-quarter of the entire state of Ohio’s reported annual oil and natural gas methane emission, or, alternatively, a substantial fraction of the annual anthropogenic methane emissions from several European countries.