It turns out I was right to be sceptical about the Howarth study claiming that shale gas production produces more greenhouse gases than coal.
Ther's now a definitive study here thoroughly debunking Howarth and showing that shale gas results in 54% less GHG production. Howarth claimed that the gap between gas produced and gas sold indicated leakage. Instead it indicates usage in powering equipment.
This is Howarth's second big mistake. His first last year was to assume that coal mining produced no methane.
Using a 100-year global warming potential and assuming an average power plant, unconventional gas results in 54% less lifecycle greenhouse gas emissions than coal does. Even using a 20-year global warming potential, as Howarth controversially argues one should, the savings from substituting unconventional gas for coal are almost 50%. The NETL study acknowledges - and explores - a range of uncertainties. But it finds nothing close to the problems that Howarth claims.