Articles | Volume 16, issue 15
Biogeosciences, 16, 3033–3046, 2019
Biogeosciences, 16, 3033–3046, 2019

Ideas and perspectives 14 Aug 2019

Ideas and perspectives | 14 Aug 2019

Ideas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane?

Robert W. Howarth

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Cited articles

Baldassare, F. J., McCaffrey, M. A., and Harper, J. A.: A geochemical context for stray gas investigations in the northern Appalachian Basin: Implications of analyses of natural gases from Neogene-through Devonian-age strata, AAPG Bull., 98, 341–372,, 2014. 
Botner, E. C., Townsend-Small, A., Nash, D. B., Xu, X., Schimmelmann, A., and Miller, J. H.: Monitoring concentration and isotopic composition of methane in groundwater in the Utica Shale hydraulic fracturing region of Ohio, Environ. Monit. Assess., 190, 322–337,, 2018. 
Burruss, R. C. and Laughrey, C. D.: Carbon and hydrogen isotopic reversals in deep basin gas: evidence for limits to the stability of hydrocarbons, Org. Geochem., 41, 1285–1296,, 2010. 
Caulton, D. R., Shepson, P. D., Santoro, R. L., Sparks, J. P., Howarth, R. W., Ingraffea, A., Camaliza, M. O., Sweeney, C., Karion, A., Davis, K. J., Stirm, B. H., Montzka, S. A., and Miller, B.: Toward a better understanding and quantification of methane emissions from shale gas development, P. Natl. Acad. Sci. USA, 111, 6237–6242,, 2014. 
Short summary
Atmospheric methane has risen rapidly since 2008 and has become more depleted in 13C, in contrast to the trend towards more 13C enrichment in the late 20th century. Many have used this isotopic evidence to infer an increased biogenic source. Here I analyze the 13C trend with the consideration that methane from shale gas is somewhat depleted in 13C compared to other fossil fuels. I conclude that shale gas may be responsible for a third of the global increase from all sources.
Final-revised paper