A recent issue of The Economist included a detailed briefing on supplies of unconventional gas around the world. The briefing presents the size of these reserves as basically a good thing, even from an environmental perspective, because gas plants emit fewer greenhouse gases per unit of electricity than coal plants do.
As has been explained here before, the question of how much climate change the world will experience is basically a matter of what total quantity of greenhouse gases humanity releases. The more fossil fuels we burn, the riskier climate change becomes. As a chart from the article shows, the world’s unconventional gas supplies are substantial:
All else being equal, the more of this gas is burned, the more climate change humanity will have to deal with. Gas extraction is also one of the world’s major sources of fugitive (unintentional) emissions of methane – a potent greenhouse gas.
Beyond climate change, the briefing does make note of some other potential environmental issues surrounding unconventional gas extraction: “Despite natural gas’s greener credentials than oil’s or coal’s, shale drilling has critics among environmentalists, who worry that water sources will be poisoned and landscapes despoiled.”
Burning gas instead of oil or coal might be an approach with climatic benefits, but the danger always exists that we will end up burning both – either simultaneously or one after the other. That would almost certainly warm the planet to an unacceptable degree.