6.4.2.2. Sinks of Atmospheric Methane

The major sink for atmospheric methane is the chemical reaction with hydroxyl radicals (OH) in the troposphere (section 1.2.1). Current removal estimates (Prather et al., 1995) are 445Mt/a. This natural process is, however, affected by the reaction of OH with other anthropogenic emissions, principally carbon monoxide (CO) and hydrocarbons from motor vehicles (Watson et al, 1990). Other sinks of atmospheric methane include stratospheric removal (again by reaction with OH) (40Mt/a) and consumption by microbial communities in the upper soils (30Mt/a). Total methane sinks are 515Mt/a (85Mt/a)