Science, Vol.327, No.5963, 322-325, 2010
Large-Scale Controls of Methanogenesis Inferred from Methane and Gravity Spaceborne Data
Wetlands are the largest individual source of methane (CH(4)), but the magnitude and distribution of this source are poorly understood on continental scales. We isolated the wetland and rice paddy contributions to spaceborne CH(4) measurements over 2003-2005 using satellite observations of gravity anomalies, a proxy for water-table depth Gamma, and surface temperature analyses T(S). We find that tropical and higher-latitude CH(4) variations are largely described by Gamma and T(S) variations, respectively. Our work suggests that tropical wetlands contribute 52 to 58% of global emissions, with the remainder coming from the extra-tropics, 2% of which is from Arctic latitudes. We estimate a 7% rise in wetland CH(4) emissions over 2003-2007, due to warming of mid-latitude and Arctic wetland regions, which we find is consistent with recent changes in atmospheric CH(4).