I finally understand methane lifetimes
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I finally understand methane lifetimes
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Re: I finally understand methane lifetimes
#2tl;dr
> I finally have some confidence that I understand how methane lifetimes work, and that for my purposes it can be summarized as:
Methane emissions decay gradually, with an average lifetime of about 12 years (“perturbation lifetime”, which is what matters for climate purposes).
This will increase by roughly 35% if methane concentrations double, or decrease roughly 25% if concentrations return to pre-industrial levels.
Re: I finally understand methane lifetimes
#3tl;dr > I finally have some confidence that I understand how methane lifetimes work, and that for my purposes it can be summarized as: Methane emissions decay gradually, with an average lifetime of about 12 years (“perturbation lifetime”, which is what matters for climate purposes). This will increase by roughly 35% if methane concentrations double, or decrease roughly 25% if concentrations return to pre-industrial l…
> This will increase by roughly 35% ...
I was a bit confused by this sentence (which is a direct excerpt from the piece). Reading the whole article, the `this` refers to the methane lifetime. Oddly (to me), the lifetime methane in the atmosphere increases with the amount of methane in the atmosphere. That's what the author has been working to understand. Very interesting!
Re: I finally understand methane lifetimes
#4tl;dr > I finally have some confidence that I understand how methane lifetimes work, and that for my purposes it can be summarized as: Methane emissions decay gradually, with an average lifetime of about 12 years (“perturbation lifetime”, which is what matters for climate purposes). This will increase by roughly 35% if methane concentrations double, or decrease roughly 25% if concentrations return to pre-industrial l…
> This will increase by roughly 35% ... I was a bit confused by this sentence (which is a direct excerpt from the piece). Reading the whole article, the `this` refers to the methane lifetime. Oddly (to me), the lifetime methane in the atmosphere increases with the amount of methane in the atmosphere. That's what the author has been working to understand. Very interesting!
It makes sense, if you take into account that, apparently, absorbing methane from the atmosphere depletes the atmosphere's capacity for absorbing methane. Hence the more methane that exists, the more methane is getting absorbed, the less capable the atmosphere is at absorbing methane.
Re: I finally understand methane lifetimes
#5Earlier quoted context omitted.
> This will increase by roughly 35% ... I was a bit confused by this sentence (which is a direct excerpt from the piece). Reading the whole article, the `this` refers to the methane lifetime. Oddly (to me), the lifetime methane in the atmosphere increases with the amount of methane in the atmosphere. That's what the author has been working to understand. Very interesting!
It makes sense, if you take into account that, apparently, absorbing methane from the atmosphere depletes the atmosphere's capacity for absorbing methane. Hence the more methane that exists, the more methane is getting absorbed, the less capable the atmosphere is at absorbing methane.
If I'm thinking clearly, using "absorbing" here implies that atmospheric concentrations of methane have an effect on the amount of methane that can be released. A lower absorption would then be "good" because it would slow the rate of accumulation of methane in the atmosphere.
The opposite is true, that the higher the methane concentration, the lower the rate of effect would be to degrade all atmospheric methane. The rates of methane accumulation and its degradation are inversely proportional beyond the limit of the atmosphere to degrade it.
Re: I finally understand methane lifetimes
#6tl;dr > I finally have some confidence that I understand how methane lifetimes work, and that for my purposes it can be summarized as: Methane emissions decay gradually, with an average lifetime of about 12 years (“perturbation lifetime”, which is what matters for climate purposes). This will increase by roughly 35% if methane concentrations double, or decrease roughly 25% if concentrations return to pre-industrial l…
(Physicist/Engineer of sorts here. Zero atmosphere knowledge)
That half life depends on concentration is not surprising to me; ethanol's half life in the blood also depends on it's concentration and the reason is rather straight forward: the liver has limited amounts of enzymes needed to process booze.
What is surprising to me, though, is that there is a mechanism that has such a massive effect at the extremely low concentrations of methane that are present in the atmosphere. Sure, OH is rare, but I'd guess is generated in large amounts in the upper atmosphere (UV + H2O -> OH- + O+ + momentum to keep them away from each other).
Does anyone here have any hard math on this?
Re: I finally understand methane lifetimes
#7Earlier quoted context omitted.
> This will increase by roughly 35% ... I was a bit confused by this sentence (which is a direct excerpt from the piece). Reading the whole article, the `this` refers to the methane lifetime. Oddly (to me), the lifetime methane in the atmosphere increases with the amount of methane in the atmosphere. That's what the author has been working to understand. Very interesting!
It makes sense, if you take into account that, apparently, absorbing methane from the atmosphere depletes the atmosphere's capacity for absorbing methane. Hence the more methane that exists, the more methane is getting absorbed, the less capable the atmosphere is at absorbing methane.
Yeah, and to simplify further, the atmosphere's got a fixed amount of methane-removing capability, and as we exceed this capability it can't absorb methane any faster, so the ratio of methane that gets absorbed starts dropping even though the amount being absorbed doesn't drop.
The reality is more complicated because the cut off is very blurry - absorbsion does still increase as methane increases, just not fast enough to keep up, and it falls further behind the more methane we put out.
Re: I finally understand methane lifetimes
#8So, hydroxide radicals (OH) break down methane (CH4) into carbon dioxide (CO2). This is a good thing for the climate, as a molecule of methane has a much bigger warming effect than CO2. (Although it is odd that the CO2 produced by methane is not counted toward methane’s overall climate impact).
There is limited OH in the atmosphere. As a result, more methane “uses up” the OH. That means that increased methane in the atmosphere results in increased lifetimes of methane. The reason carbon monoxide (CO) has three times the warming potential of CO2 is because CO uses OH, increasing methane!
So, why not produce a bunch of OH? Because OH has a half life of less than a second. Hmm.
However, aerosolized plant terpenes (such as produced by wetlands) are a natural source of OH in the atmosphere.
Interesting. Perhaps this should change the calculation of the carbon credits due to terpene generating biomes (above and beyond the carbon sequestered by the plants). Or, maybe we could mass produce terpenes to clean out atmospheric methane (e.g., after a pipeline leak or something).
Anyone know more?
Re: I finally understand methane lifetimes
#9Earlier quoted context omitted.
> This will increase by roughly 35% ... I was a bit confused by this sentence (which is a direct excerpt from the piece). Reading the whole article, the `this` refers to the methane lifetime. Oddly (to me), the lifetime methane in the atmosphere increases with the amount of methane in the atmosphere. That's what the author has been working to understand. Very interesting!
It makes sense, if you take into account that, apparently, absorbing methane from the atmosphere depletes the atmosphere's capacity for absorbing methane. Hence the more methane that exists, the more methane is getting absorbed, the less capable the atmosphere is at absorbing methane.
Which to me raises the question: Are there any possibilities to increase the absorption of methane somehow?
And it seems like there are methods for capturing methane: https://news.mit.edu/2022/dirt-cheap-solution-common-clay-ma...
Re: I finally understand methane lifetimes
#10So, hydroxide radicals (OH) break down methane (CH4) into carbon dioxide (CO2). This is a good thing for the climate, as a molecule of methane has a much bigger warming effect than CO2. (Although it is odd that the CO2 produced by methane is not counted toward methane’s overall climate impact). There is limited OH in the atmosphere. As a result, more methane “uses up” the OH. That means that increased methane in the…
> the CO2 produced by methane is not counted toward methane’s overall climate impact
It definitely is in some contexts. It's often cited in CO2 equivalent over time. Methane start off to be something like 80 times more potent as a greenhouse gas than CO2. Then as it decays to CO2 its impact is that of CO2 but time has to be accounted for. So for every ton of methane, you can estimate an equivalent CO2 tonnage over then next, say, 50 years.
A quick search for methane co2 equivalent reveals a site claiming methane has 25 times more global warming potential than CO2 over 100 years.