Impact of El Nino-Southern Oscillation on the interannual variability of methane and tropospheric ozone

摘要

The interannual variability of the greenhouse gases methane (CH4) and tropospheric ozone (O-3) is largely driven by natural variations in global emissions and meteorology. The El Nino-Southern Oscillation (ENSO) is known to influence fire occurrence, wetland emission and atmospheric circulation, affecting sources and sinks of CH4 and tropospheric O-3, but there are still important uncertainties associated with the exact mechanism and magnitude of this effect. Here we use a modelling approach to investigate how fires and meteorology control the interannual variability of global carbon monoxide (CO), CH4 and O-3 concentrations, particularly during large El Nino events. Using a threedimensional chemical transport model (TOMCAT) coupled to a sophisticated aerosol microphysics scheme (GLOMAP) we simulate changes to CO, hydroxyl radical (OH) and O-3 for the period 1997-2014. We then use an offline radiative transfer model to quantify the climate impact of changes to atmospheric composition as a result of specific drivers.