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.