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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.
"We have produced the first comprehensive analysis of the greenhouse gas footprint of shale gas," said lead author Robert Howarth from Cornell University in Ithaca, US.
"We have used the best available data [and] the conclusion is that shale gas may indeed be quite damaging to global warming, quite likely as bad or worse than coal," he told BBC News.
"We should not proceed to view shale gas as a 'transitional fuel' to be used over the next few decades to replace other fossil fuels”
Figures from the US government and industry indicate that at least a third more methane leaks from shale gas extraction than from conventional wells - and perhaps more than twice as much.
Molecule for molecule, methane is a much more potent greenhouse gas than CO2; but it lasts for a much shorter time in the atmosphere.
Figures from this research team indicate that over a 20-year period, the net warming impact of using shale gas is worse than coal - and, perhaps more surprisingly, that conventional gas may be worse than coal as well.
Over a 100-year timeframe, conventional gas is almost certainly better than coal - but shale gas could be worse.
The precise numbers depend most on leakage rates. Dr Howarth's group used "best practice" estimates; in the real world, therefore, the leakage and the climate impact could be even worse.
"No-one knows for sure to what extent industry uses best practices; and unfortunately, at least in the US, industry does not want government or the public to know," he said.
http://www.bbc.co.uk/news/science-environment-13053040
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The shale gas industry has a long way to go before they can be trusted. They don't even have to say what's in the millions of litres of hydraulic fluid they use and waste.
One wonders will the last 50% of fossil fuels we use cause much more damage than the first 50%, even with efficiency gains.
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