The atmospheric cycle of methane

This is the authors' abstract. We don't add key points for this paper.

The atmospheric distribution of CH4 is rather uniform zonally and vertically but exhibits a slight gradient with latitude in the troposphere; in the stratosphere it shows a definite decrease with altitude. The average volume mixing ratio in the troposphere is 1.4 ppm which corresponds to a total amount of 4 × 1015 g of CH4 present in the atmosphere. Most is of recent biologic origin. C14 analyses show that no more than 20% is released by fossil sources. The various ecosystems producing CH4 are discussed and the total annual production is estimated to lie between 5.5 × 1014 g/yr and 11 × 1014 g/yr. The corresponding turnover times for atmospheric CH4 range from 4 to 7 yr. The destruction of CH4 takes place mainly in the troposphere, most probably through the reaction CH4 + OH → CH3 + H2O. About 10% of the CH4 is destroyed in the stratosphere. The CH4 cycle is strongly coupled to the H2 and CO cycles and contributes also on the order of 1% to the atmospheric carbon cycle.DOI: 10.1111/j.2153-3490.1974.tb01952.x