Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions

Benjamin Hmiel, V. V. Petrenko, Michael Dyonisius, Christo Buizert, Andrew Smith, Philip Place, Christina M. Harth, Ross Beaudette, Quan Hua, Bin Yang, Isaac Vimont, Sylvia Michel, Jeffrey P. Severinghaus, David Etheridge, Tony Bromley, J. H. M. M. Schmitt, Xavier Faïn, Ray F. Weiss, E. J. Dlugokencky