Given a figure of 1 tonne of CO2e methane emissions, where the CO2e figure is calculated using the 100-year global warming potential, is it possible to do a straight conversion back to tonnes of methane emitted, and then forward again to tonnes of CO2e using the 20-year global warming potential. I.e.:
100 year GWP for methane = 28
20 year GWP for methane = 84
1 tonne CO2e / 28 = 0.0357 tonnes methane emitted
0.0357 * 84 = 3 tonnes CO2e at GWP20
Or is there more to the GWP100 calculations which aren't purely captured by the factors I've given above?