T, yes, the entire quantity of atmospheric methane must be replaced every 7 years to just stay stable. We (now with the help of melting permafrost and clathrates) are producing enough more than enough to do that on a continual basis. I don't find that comforting.
But yes, if we could find ourselves a way to stop our emission, our part of that extra methane would fairly quickly go away, and we could only pray that it would not be taken up by the methane feedbacks that already seem to be kicking in. Unfortunately, we have turned heavily toward NG production, and it is proving to be very hard not to let a good portion of that escape directly into the atmosphere (seen most dramatically in CA right now, but it is a chronic issue throughout the industry, afaics. And then there are little things like rice growing, and cattle and sheep raising the latter two of which no one around here seems to want to take very seriously.
But thinking about all of this prompted some questions in my brain that I don't know the answers to right off:
One thing saving us from the full impact of super high atmospheric CO2 concentrations is its absorption into the oceans. Does anyone know how much this is also a factor with methane? Does atmospheric methane dissolve in water easily? What portion (if any) of our emissions of methane are being absorbed by oceans? When (and if) absorbed, does it form an acid, like CO2 does?
I can't recall reading anything about this either way (and I'm too damn lazy right now to look up the chemistry myself
).