There is emerging evidence that the far more alarming issue around the natural gas boom in the country is less about fracking (yes, there was some contaminated ground water that you could ignite when it came out of the sink like in the documentary, but of late fracking wells are now constructed more safely, so the argument goes) and much more about methane leaks from the mining of natural gas. Unburned methane that enters the atmosphere is far worse for global warming than carbon dioxide. Very interesting article on this by 538:
http://fivethirtyeight.com/features/the-natural-gas-boom-could-accelerate-climate-change/