Methane is a potent greenhouse gas and an important sink of atmospheric OH radicals, which determine the global atmospheric oxidation capacity. CH4 has increased since pre-industrial times until the year 2000, after which its global concentration has remained relatively stable. Since 2007, it is rapidly increasing again for reasons that are not well understood. The current paper analyses source specific methane emissions that are likely responsible for the recent increase. Global CH4 sources are determined using variational inversion based on measurements of methane and its isotope signatures (δ13C). This latter provide better constraints on the contributions of microbial and fossil fuel CH4 sources than the concentrations alone. The analysis points to a more strongly increasing contribution of microbial sources since 2007 than predicted by previous assessments (Global Carbon Project). These findings have the potential to lead to a major reassessment of the global methane budget.