It's even more complicated than that, because you have constant emissions, and these models are based on the decay of a some starting amount of CH4. With constant replenishment of CH4, the process is more correctly modeled as a continuous stirred tank reactor (CSTR), a classic chemical engineering process. In CSTR's, you can have rate limited or reactant limited processes. Reactant limited would be the case of running out of -OH radicals to cleave the CH4. Rate limited would be where you have more than enough -OH and it really depends on the reaction kinetics. Perturbation lifetimes are not really a thing for the world we live in, as there is a constant release and oxidation of CH4. Nobody is dumping 50% (or whatever other percentage) of the annual amount at one go. Real life has a lot of moving parts.
Steve, now that you've looked at CH4, can you help me on the atmospheric lifetime of CO2? Often I read that it's a hundred years or more. Yet we know from the sawtooth edge of the Keeling curve that a lot of CO2 leaves the atmosphere every summer, ending its "atmospheric lifetime." When the C atom of any CO2 molecule goes back to the atmosphere after a sojourn at or just below Earth's surface (terrestrial or ocean), it doesn't have the same two O atoms it came attached to, but two different ones. Don't we than have to say then that the atmospheric lifetime of a CO2 molecule is on average only a couple of years?
The INVENTORY of CO2 in the atmosphere is not apt to go down over 100 years even if all human-influenced emissions of it ended today . That can maybe be called "long-lived" in contrast to CH4, the inventory of which would go down fast if even a part of human-influenced emissions (say for fun fossil-fuel related) ended today.
I agree with your seven words of wisdom wholeheartedly, especially "methane first." If the world could stop increasing annual natgas withdrawals, after about ten years of no increases CH4 would no longer add to climate forcing. It would sustain it at the t + 10 year level, though, and that would be a lot. If withdrawals could be lowered for ten years, climate forcing by methane would be lessened, leading to relative cooling after t + 10 years. Better yet!
My question about CO2 atmospheric lifetime comes from curiosity and wonder about how the fast, AKA biogenic, carbon cycle actually works. The annual flux between atmosphere and surface of planet Earth is said on good authority (references on request :-) ) to be about 770 Gt CO2/year. If it's that massive, why are the peaks and valleys of the Keeling curve only about 5 ppm apart? Possibly the northern and southern hemispheres offset each other seasonally (though northern has more terrestrial biomass than southern)?
We agree, you and I, that the inventory of CO2 in the atmosphere, the mass of CO2, would decrease very little over the next century even if tomorrow we ended fossil fuel processing, shut down cement factories and stopped deforestation and human-caused desertification. My big wide pedantic streak bridles on hearing implications (not from you) that CO2 in the atmosphere is irreducible, immutable for decades. To me, that working model shows a sad lack of appreciation for the wondrous earth system called the global carbon cycle.
I'll peg away at it. Several days ago you kindly told me an e-mail address for yourself, but it bounced.
It was steve[at]snewman[dot]net error message said host unknown. In case I find a link that might whet your curiosity, would you mind obliging me again with an e-mail address? Cheers
Very nice work. I was looking for this information a day ago because this was a question posed to me by my dad. I couldn't find anything remotely like this in the paywalled literature. Excellent and clear summary.
You say.... "This will increase by roughly 35% if methane concentrations double, or decrease roughly 25% if concentrations return to pre-industrial levels."
A couple of Monkey Wrench Numbers for you... 80% of Methane is generated by wetlands... The Gov policy in the US in the 80's, 90's started the "Protect the wetlands" policy where they called a puddle in a field a protected wetland... How much of this "wetland" creation increased Methane production? And you didn't give a number to the Clathrate bed release of ancestral Methane shaken loose by undersea volcano heat and "plate scrape".... Just trying to help...
More aptly, I would suggest always TEST the numbers to understand what they mean and not what those who quote them say they mean. This is doing your own research and takes much more work (thought) than finding a YouTube video that agrees with one's beliefs. This implies we need to be prepared to accept a new conclusion.
I love this breakdown -- thank you!
Great! How about tackling the Global Warming Potential metrics for methane next?
Simply awesome breakdown - thanks a lot for explaining what you learned so clearly.
Are you on Twitter? There was a discussion between Glen Peters, Zeke Hausfather, Michelle Cain and others yesterday https://twitter.com/Peters_Glen/status/1519568344084533250
It's even more complicated than that, because you have constant emissions, and these models are based on the decay of a some starting amount of CH4. With constant replenishment of CH4, the process is more correctly modeled as a continuous stirred tank reactor (CSTR), a classic chemical engineering process. In CSTR's, you can have rate limited or reactant limited processes. Reactant limited would be the case of running out of -OH radicals to cleave the CH4. Rate limited would be where you have more than enough -OH and it really depends on the reaction kinetics. Perturbation lifetimes are not really a thing for the world we live in, as there is a constant release and oxidation of CH4. Nobody is dumping 50% (or whatever other percentage) of the annual amount at one go. Real life has a lot of moving parts.
Steve, now that you've looked at CH4, can you help me on the atmospheric lifetime of CO2? Often I read that it's a hundred years or more. Yet we know from the sawtooth edge of the Keeling curve that a lot of CO2 leaves the atmosphere every summer, ending its "atmospheric lifetime." When the C atom of any CO2 molecule goes back to the atmosphere after a sojourn at or just below Earth's surface (terrestrial or ocean), it doesn't have the same two O atoms it came attached to, but two different ones. Don't we than have to say then that the atmospheric lifetime of a CO2 molecule is on average only a couple of years?
The INVENTORY of CO2 in the atmosphere is not apt to go down over 100 years even if all human-influenced emissions of it ended today . That can maybe be called "long-lived" in contrast to CH4, the inventory of which would go down fast if even a part of human-influenced emissions (say for fun fossil-fuel related) ended today.
Thanks for your response, Steve
I agree with your seven words of wisdom wholeheartedly, especially "methane first." If the world could stop increasing annual natgas withdrawals, after about ten years of no increases CH4 would no longer add to climate forcing. It would sustain it at the t + 10 year level, though, and that would be a lot. If withdrawals could be lowered for ten years, climate forcing by methane would be lessened, leading to relative cooling after t + 10 years. Better yet!
My question about CO2 atmospheric lifetime comes from curiosity and wonder about how the fast, AKA biogenic, carbon cycle actually works. The annual flux between atmosphere and surface of planet Earth is said on good authority (references on request :-) ) to be about 770 Gt CO2/year. If it's that massive, why are the peaks and valleys of the Keeling curve only about 5 ppm apart? Possibly the northern and southern hemispheres offset each other seasonally (though northern has more terrestrial biomass than southern)?
We agree, you and I, that the inventory of CO2 in the atmosphere, the mass of CO2, would decrease very little over the next century even if tomorrow we ended fossil fuel processing, shut down cement factories and stopped deforestation and human-caused desertification. My big wide pedantic streak bridles on hearing implications (not from you) that CO2 in the atmosphere is irreducible, immutable for decades. To me, that working model shows a sad lack of appreciation for the wondrous earth system called the global carbon cycle.
I'll peg away at it. Several days ago you kindly told me an e-mail address for yourself, but it bounced.
It was steve[at]snewman[dot]net error message said host unknown. In case I find a link that might whet your curiosity, would you mind obliging me again with an e-mail address? Cheers
Very nice work. I was looking for this information a day ago because this was a question posed to me by my dad. I couldn't find anything remotely like this in the paywalled literature. Excellent and clear summary.
You say.... "This will increase by roughly 35% if methane concentrations double, or decrease roughly 25% if concentrations return to pre-industrial levels."
A couple of Monkey Wrench Numbers for you... 80% of Methane is generated by wetlands... The Gov policy in the US in the 80's, 90's started the "Protect the wetlands" policy where they called a puddle in a field a protected wetland... How much of this "wetland" creation increased Methane production? And you didn't give a number to the Clathrate bed release of ancestral Methane shaken loose by undersea volcano heat and "plate scrape".... Just trying to help...
More aptly, I would suggest always TEST the numbers to understand what they mean and not what those who quote them say they mean. This is doing your own research and takes much more work (thought) than finding a YouTube video that agrees with one's beliefs. This implies we need to be prepared to accept a new conclusion.