CH₄ sources estimated from atmospheric observations of CH₄ and its ¹³C/¹²C isotopic ratios: 1. Inverse modeling of source processes

摘要

A time-dependent inverse modeling approach that estimates the global magnitude of atmospheric methane sources from the observed spatiotemporal distribution of atmospheric CH, C-13/C-12 isotopic ratios, and a priori estimates of the source strengths is presented. Relative to the a priori source estimates, the inverse model calls for increased CH flux from sources with strong spatial footprints in the tropics and Southern Hemisphere and decreases in sources in the Northern Hemisphere. The CH and C-13/C-12 isotopic ratio observations suggest an unusually high CH flux from swamps (similar tO00 ± 44 Tg CH/yr) and biomass burning (88 ± 18 Tg CH/yr) with relatively low estimates of emissions from bogs (similar tO0 ± 14 Tg CH/yr), and landfills (35 ± 14 Tg CH/yr). The model results support the hypothesis that the 1998 CH growth rate anomaly was caused in part by a large increase in CH production from wetlands, and indicate that wetland sources were about 40 Tg CH/yr higher in 1998 than 1999. [References: 71]