Feedbacks depend on which model you use. Still, it's not particularly relevant to the question of slow methane leakage from a natural gas distribution system, which is what we're talking about.
Sure it's relevant. If we use twice as much methane this year, we'll probably have twice as much leakage, and that means twice as much climate impact from this year's methane over the next few decades.
The feedbacks depend on total temperature not atmospheric gas composition, so methane raising temperatures by X degrees isn't any worse than CO2 causing the same temperature rise, and methane will exit the atmosphere faster. That is, feedback is proportional to the time integral of warming, not the forcing!
Yeah fine but total warming over the next 25 years could well be sufficient to get us over the critical threshold, and methane does have a greater impact than CO2 over a period of 25 years.
