| Summary: | 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 Γ, and surface temperature analyses T_S. We find that tropical and higher-latitude CH_4 variations are largely described by Γ 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. © 2010 American Association for the Advancement of Science. 20 April 2009; accepted 11 November 2009. We thank J. Melack for providing feedback on the manuscript and R. Hipkin and F. Simons for assistance with GRACE gravity data. This work is funded by United Kingdom Natural Environmental Research Council studentship NE/F007973/1 and the National Centre for Earth Observation. Supplemental Material - Bloom.SOM.pdf
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