Methane is the game changer.  Methane emissions, driven by natural gas, are one hundred times worse for climate change than CO2.  If we don't get these under control, the game is over for human life on our planet.  Download
Robert Howarth's paper ese3.35.pdf  from web address - http://onlinelibrary.wiley.com/doi/10.1002/ese3.35/pdf