[tremon]

it can take 20 years, during which that single carbon atom yields 20x the global warming potential

Actually, it's more than that. The 20x global warming potential of CH4 is based on a 100-year average, which is the yardstick unit of measurement in the scientific literature. But as you say, methane degrades in 20 years so its average-20x contribution happens within those 20 years:

> The IPCC reports that the global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe [..] and 105 times the effect when accounting for aerosol interactions

-- from https://en.wikipedia.org/wiki/Atmospheric_methane?useskin=ti...