We find (i) measurements at all scales show that official inventories consistently underestimate actual CH4 [methane] emissions, with the natural gas and oil sectors as important contributors; (ii) many independent experiments suggest that a
small number of «super-emitters» could be responsible for a large fraction of
leakage; (iii) recent regional atmospheric studies with very high emissions
rates are unlikely to be representative of typical natural gas system
leakage rates; and (iv) assessments using 100 - year impact indicators show system - wide
leakage is unlikely to be large enough to negate climate benefits of coal - to - natural gas substitution.