Modeling the Sudden Decrease in CH4 Growth Rate in 1992

A two-dimensional global chemistry model is developed to study the distribution and long-term trends of methane. The model contains 34 species and 104 chemical and photochemical reactions. Using the model, the long-term trends of CH4, CO and OH in at-mosphere are simulated, comparison between the model and observations shows that the simulation is successful. Experiments are done to investigate the causes of dramatic decrease in the growth rate of CH4, in 1992 such as OH increase due to stratospheric ozone depletion, decrease of tempera?ture in the troposphere due to Mount Pinatubo eruption and descendent of CH4 sources fluxes. A new explanation is proposed and verified by this model that the decrease of CO emission plays an important role for the abnormal growth rate of CH4 in 1992. We find that the de?creases of CH4 and CO emissions are the main reasons for the sudden decrease of growth rate of CH4 in 1992, which account for 73% and 27% respectively.