Okay, so you do know. But then why here don't you distinguish between a more-or-less constant fixed increase in warming by having a large population of cows on the Earth (compared to what there was historically, for instance)--fixed because the residence time for methane is short compared to how quickly we're likely to make big changes in things like cow populations--and the continual accumulation of CO2 (which won't return to baseline for a long time compared to how rapidly we can change our technology to dramatically reduce net carbon export).

If we could have fewer cows, it wouldn't solve the long-term problem, but it might buy us a few more years to get our CO2 addiction under control.