You’re vastly off. Averaged over 20 years methane is (GWP) 104x as potent as CO2, averaged over 100 years it’s (GWP) 28x. But, to get that average you can calculate ((28 * 100) - (104 * 20)) / 80 = 9. So, from year 20 to year 100 it’s 9x as potent on average. You get this because 1 - (1/(2^(20/7)) = 86% of methane released today has broken down in 20 years.
Further, methane goes from CH4 atomic weight 18 to CO2 atomic weight 44. Thus, after breakdown you get (44/18) = 2.75x as much CO2 by weight. So, in 2120 methane produced today will be 99.995% CO2 and provide ~2.75x as much warming vs CO2 emitted today.
That makes sense. Do you know if there is a graph that illustrates this so it cements in my mind better?
I wonder how much feedbacks are considered with this. The early pulse of warming can cause changes to alebedo, co2 and methane emissions from melting permafrost, etc that carry on after the initial methane has broken down.
Further, methane goes from CH4 atomic weight 18 to CO2 atomic weight 44. Thus, after breakdown you get (44/18) = 2.75x as much CO2 by weight. So, in 2120 methane produced today will be 99.995% CO2 and provide ~2.75x as much warming vs CO2 emitted today.
Edit: Updated with numbers from https://en.wikipedia.org/wiki/Atmospheric_methane