Comment on Ideas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane? by Robert W. Howarth (2019)

Abstract. The ideas and perspectives presented by Howarth (2019) on shale gas being a major cause of recent increases in global atmospheric methane are based on his notion that stable carbon isotopes of methane (δ13C1) of shale gas are lighter than that of conventional gas based on a meager and unrepresentative data set. A plethora of publicly available data show that the δ13C1 values of shale gas are typically heavier than those of conventional gas. This contradiction renders his ideas, perspectives, and calculations on methane emissions from shale gas invalid.