The 3 D global tropospheric model MOGUNTIA was used in a 25-year scenario study to analyse the effects of increasing methane emissions on the oxidising capacity of the atmosphere and methane's contribution to climate forcing. The CH4-emission-reducing measures were for efficiency compared to a continuation of the current trends. The feasibility of a Joint Implementation policy realising these reductions was also brought into focus. This report also gives background information on the methane chemistry and the sources of atmospheric methane.