I'm not sure how long (absent intelligent policy) til we hit peak natural gas and the balance naturally shifts back towards dirty energy sources.
I.e. policy helps, but economics had as much to do with it
Coal CO2 emissions are almost double natgas' [1]. While it is true that natgas is mainly CH4, a highly potent GG, its atmospheric lifetime is about 8 yrs. Further, the only way the methane would be getting into the air is via leaks in upstream/midstream processes. Today, hardly any of this leaks (EPA estimates leak rate of 1.4%).
Now addressing fracking, the drilling and fracturing process are the cause of little to no environmental impact/damage. The culprit is wastewater injection. This is the unknown, and while the EPA found no evidence of widespread or systemic pollution of water resources due to the fracking process (which includes WWI before the well is capped), it did highlight the potential in several stages of production for contamination to occur.
Now that said, the damage natgas causes, from E&P (especially) to burn, pales in comparison to coal's at any stage.
I think it would be beneficial for HN users to spend some time in the energy industry before making baseless claims.
There's also a defence of the original study https://link.springer.com/article/10.1007/s10584-012-0401-0#...