Comment by brendoelfrendo

No, quickly is correct. Methane in the atmosphere has a lifespan of about 12 years, if I recall correctly. That means that if you stop emitting it, then the warming effect of atmospheric methane would subside over the course of a decade. This is as compared to CO2, which is a much weaker greenhouse gas, but does not break down naturally over time. Atmospheric CO2 has to be absorbed by natural processes (oceanic absorption, plant photosynthesis, etc) otherwise it exists in the atmosphere effectively forever.