Marcellus shale gas not so clean

And now this: A Cornell University study has concluded that methane produced from shale gas may contribute as much or even more to global greenhouse warming than coal. Shale gas is lost to the atmosphere by venting from backflow water released from wells and pressure valves, along with leaks that can occur in the various equipment used to produce, process and ship the gas, as well as in gas pipelines used to ship it to market.

See http://www.post-gazette.com/pg/11103/1138900-84.stm.