It’s true that gas produces only half as much CO2 as coal. BUT, shale gas is primarily composed of methane, which is also a greenhouse gas – and it’s 86 times more devastating than CO2 when measured over a 20-year period. This means that if more than 3 percent of the methane extracted escapes into the atmosphere unburned, the warming effect will be the same as if you had burned coal.
Studies from around the world have shown that leaking methane from gas infrastructure – wells, pipelines, storage tanks, flaring gas wells – all leak at levels above – often well-above – the minimum safe level. Therefore, methane is now considered to be one of the main contributors to climate change, and the fastest growing.