Due to the removal of OH radical as CH4 concentration increases, a suitable model to increase the CH4 lifetime as this happens needs to be created. More detail will be added later, but I expect the implementation will be similar to the one currently in place for carbon, whereby the lifetime is multiplied by a factor, which is recalculated at each step. IPCC AR5 CH8 suggests this factor should depend on CH4 concentration anomaly.
Due to the removal of OH radical as CH4 concentration increases, a suitable model to increase the CH4 lifetime as this happens needs to be created. More detail will be added later, but I expect the implementation will be similar to the one currently in place for carbon, whereby the lifetime is multiplied by a factor, which is recalculated at each step. IPCC AR5 CH8 suggests this factor should depend on CH4 concentration anomaly.