ORIGINS OF ATMOSPHERIC METHANE

Methane, an important atmospheric trace gas, controls numerous chemical processes and species in the troposphere and stratosphere. It is a strong greenhouse gas with a significantly adverse environmental impact. Methane's concentration in the Earth's atmosphere has been increasing at a rate of about 1% per year during this century, and reached 1.72 ppm (by volume) in 1990. In this study, the individual sources of methane are identified and discussed. Available estimates of emission rates from these sources are presented. About 80% of methane in the atmosphere is produced biologically, whereas about 50% of the present sources are controlled by mankind. The accuracy of available estimates of emission rates, from individual sources, is poor; so more field measurements are still required for a more satisfactory evaluation of methane sources.