Fig. 4
Change in average annual biogenic and fossil fuel emissions. Change in average annual fossil fuel (a) and biogenic (b) emissions between the 2001–2006 and 2007–2014 periods needed to fit the CH4 mole fraction for different assumptions about biomass burning emissions and the isotopic signatures of the methane emission sources. These values are calculated for different proposed changes in biomass burning emissions: GFED4s = 2.1 ± 1.1 Tg CH4 per year, this study = 3.7 ± 1.4 Tg CH4 per year, and no change = 0.0 Tg CH4 per year. The isotopic signatures assigned to each source type are shown in Table 1. The error bars are the 1σ uncertainties, which are calculated by propagating the uncertainties of the source isotopic signatures, biomass burning perturbations, and total perturbations needed to fit the growth rate and isotope measurements (see iso-mf scenario in Fig. 3)
