The Cornell research team which published a critical study about shale gas in 2011 has improved its methodology and has come to the same conclusion: shale gas "is inadequate as a bridge fuel and may be worse for climate change in the long run than coal".

(Source: DeSmogBlog)
Can shale-gas methane emissions be reduced? Clearly yes, and proposed EPA regulations to require capture of gas at the time of well completions are an important step. Regulations are necessary to accomplish emission reductions, as economic considerations alone have not driven such reductions. And it may be extremely expensive to reduce leakage associated with aging infrastructure, particularly distribution pipelines in cities but also longdistance transmission pipelines, which are on average more than 50 years old in the U.S. Should society invest massive capital in such improvements for a bridge fuel that is to be used for only 20 to 30 years, or would the capital be better spent on constructing a smart electric grid and other technologies that move towards a truly green energy future?”