By Richard Black, Environment Correspondent, BBC News

“Drawn from rock through a controversial “fracking” process, some hail the gas as a “stepping stone” to a low-carbon future and a route to energy security.

“But US researchers found that shale gas wells leak substantial amounts of methane, a potent greenhouse gas.

This makes its climate impact worse than conventional gas, they say – and probably worse than coal as well.

” ‘Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon, and is comparable over 100 years,’ they write in a paper to be published shortly in the journal Climatic Change. . .”