It decomposes to CO2 and water vapor over about 10 years. The more methane we pump out, the longer decomp takes because there are fewer atmospheric hydroxyl radicals to drive the reaction.
The methane cycle I'm familiar with is related to things dying and getting buried underground or in the ocean. I don't think there is any comparable process to how photosynthesis consumes CO2. There are methanogen bacteria who consume it, but that's probably not a globally scalable solution. I think it would be cheaper just to capture and store it.
Water (the stable form of hydroxyl + hydrogen, we can't disperse radicals at the atmosphere) is a powerful greenhouse gas and will offset a lot of the cooling you may get by it.
This is really fascinating, thanks for the clarification.
I know that data for CO2 concentrations in the atmosphere go back at least 541m years, i.e. the whole Phanerozoic. Does a similar dataset exist for methane?
The biggest spike in the Phanerozoic was at the Permian extinction event 251m years ago and was caused by huge volcanic eruptions in Siberia that burned off coal deposits created in the Carboniferous era. See Figure 7 in this publication.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200...
The methane cycle I'm familiar with is related to things dying and getting buried underground or in the ocean. I don't think there is any comparable process to how photosynthesis consumes CO2. There are methanogen bacteria who consume it, but that's probably not a globally scalable solution. I think it would be cheaper just to capture and store it.