Three decades of global methane sources and sinks - Kirschke,S; Bousquet,P; Ciais,P; Saunois,M; Canadell,JG; Dlugokencky,EJ; Bergamaschi,P; Bergmann,D; Blake,DR; Bruhwiler,L; Cameron-Smith,P; Castaldi,S; et al. (NATURE GEOSCIENCE, 2013)