Methane, carbon monoxide and methylchloroform in the Southern Hemisphere

New observational data on CH4, CO and CH3CCl3 in the Southern Hemisphere are reported. The data are analyzed for long term trends and seasonal cycles. CH3CCl3 data are used to scale the OH fields incorporated in a two-dimensional model, which in turn, is used to constrain the magnitude of a global CH4 source function. The possible causes of observed seasonality of CH3CCl3, CH4 and CO are identified, and several other aspects of observed CH4 variability are discussed. Possible future research directions are also given.