ATMOSPHERE METHANE TRENDS OVER THE LAST 150 YEARS

With two long-term emission scenarios of CH4, long-term trends of CH4 are simulated by using a global two-dimensional chemistry model. The modeled CH4 concentrations have a good agreement with observation. The results show that the concentration and emissions of CH4 are 760×10-9V/V and 280×109 kg before industrial revolution, 1611.9×10-9V/V and 533.9×109 kg in 1991, Simulated number concentrations of OH radicals are 7.17×105/cm3 in 1840,5.79×105/cm3 in 1991, and will be 5.47×105/cm3 in 2020. The increase trend of atmospheric CH4 is caused by the increase of emission of CH4 and decrease of OH radicals.