11 ms·

I finally understand methane lifetimes

213 points by gk1 5y ago

Melatonic 5y ago
Don't forget about those deep ocean Methane Clathrates !
wrycoder 5y ago
tl;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.
- thatcherc 5y ago
  > 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!
  - rocqua 5y ago
    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.
    - washadjeffmad 5y ago
      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.
    - scratcheee 5y ago
      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.
    - mudita 5y ago
      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-materials-may-help-curb-methane-emissions https://news.mit.edu/2022/dirt-cheap-solution-common-clay-ma...
- amateurICEguy 5y ago
  (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?
  - twic 5y ago
    FWIW, and this is a rather minor and pedantic point, these are hydroxyl radicals, not hydroxide ions, so it's: H2O + γ -> OH• + H• Rather than: H2O + γ -> OH- + H+ Oh, and whichever way, H2O splits into OH and H, not OH and O, but i assume that was a typo!
    - robocat 5y ago
      > OH• https://en.wikipedia.org/wiki/Hydroxyl_radical https://en.wikipedia.org/wiki/Hydroxyl_radical “Notation: The unpaired electron of the hydroxyl radical is officially represented by a middle dot, •, beside the O.” Note that article uses a superscripted dot <sup>•</sup>OH, and the dot is usually prefixed in the article (presumably so as to put the dot next to the O that doesn’t have a full shell?). However the article sometimes suffixes the dot, to put it beside the R organic radical. Weird.
dr_dshiv 5y ago
So, 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?
- tejohnso 5y ago
  > 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.
  - dr_dshiv 5y ago
    Here is a source explaining why the CO2 produced by methane isn’t counted in estimates of global warming potential. It seems to come down to the different calculations required for anthropogenic sources. https://ghginstitute.org/2010/07/13/what-is-different-about-methane-ch4-emissions-the-forgotten-co2-in-ghg-emissions-accounting/ https://ghginstitute.org/2010/07/13/what-is-different-about-...
- alexose 5y ago
bricemo 5y ago
Beyond methane and climate change, this is a lovely step through of simply grappling with a new concept to understand it, one site/paper at a time. I wish I could teach my parents how to do this, they never get beyond the first page
photochemsyn 5y ago
Additional source describing the difference between CH4 and CO2 in the atmosphere: > "Methane makes up just 0.00018 percent of the atmosphere, compared to 0.039 percent for carbon dioxide. (CO2 is roughly 200 times more abundant.) Yet scientists attribute about one-sixth of recent global warming to methane emissions; what methane lacks in volume it makes up for in potency. Over a 20-year period, one ton of methane has a global warming potential that is 84 to 87 times greater than carbon dioxide. Over a century, that warming potential is 28 to 36 times greater. The difference occurs because methane is mostly scrubbed out of the air by chemical reactions within about ten years, while carbon dioxide persists in the atmosphere for much longer than a century." https://earthobservatory.nasa.gov/features/MethaneMatters https://earthobservatory.nasa.gov/features/MethaneMatters A big uncertainty is the future of permafrost and shallow marine sediments, which store carbon in various forms. Some scenarios are, well, not good: https://climatemodeling.science.energy.gov/presentations/impact-methane-clathrate-emissions-earth-system https://climatemodeling.science.energy.gov/presentations/imp... > "Our simulations include a plausible release from clathrates in the Arctic that increases global methane emissions by 22%, as well as a scenario with 10 times those clathrate emissions. The CESM model includes a fully interactive physical ocean... The results indicate that such Arctic clathrate emissions (1) increase global methane concentrations by an average of 38%, non-uniformly; (2) increase surface ozone concentrations by around 10% globally, and even more in polluted regions; (3) increase methane lifetime by 13% ..." It's kind of like defrosting a freezer full of 25,000 year old fish guts...
paultgriffiths 5y ago
Very interesting, and a great description of methane self-feedback. The perturbation lifetime analysis - the idea that the time constant of the atmospheric response to methane is longer than the time constant of the reaction that removes methane - comes from a beautiful paper by Michael Prather that may be of interest to anyone with some linear algebra. See https://unfccc.int/files/meetings/workshops/other_meetings/application/pdf/prather1994.pdf https://unfccc.int/files/meetings/workshops/other_meetings/a....
boringg 5y ago
It's this level of understanding that can't be pushed out to the general population. It is far too complicated for people to grasp. Add on to these complexities is that if we are trying to price carbon - the impacts change with the concentrations in the atmosphere. The market needs to be dumbed down to simplistic values (which thankfully they have) so that we have a sense on where to target and incentivize change for policy makers otherwise it is far to easy for mud-rakers to try and undo meaningful work/change in our policy/business arenas. Abstract away the complications. Great piece.
- nverno 5y ago
  I think it is the dumbing down that makes it easier for mud-rakers. People know it's complicated anyway, and the average person can grasp complicated things as well as you.
  - deleted 5y ago
    [deleted]
  - Enginerrrd 5y ago
    As an environmental engineer that deals with the interface between the public and policy makers, I think I'm inclined to agree with you. The public IS dumb, but every time they try to dumb down the principles they regulate on, it always comes at the detriment of the environment and the 'little guy'. It's almost always better to delegate policy to smart qualified people with correctly aligned interests. Getting that latter part right is hard, but that is the job of a competent public official.
    - boringg 5y ago
      It's a difficult place to be - damned if you do and damned if you don't.
  - boringg 5y ago
    I disagree. There is an inherent risk that dumbing down or abstracting away the complexities of the science to have an appropriate discourse on appropriate policy action creates blowback but trying to create a system that accounts for the complexities of the science would just cause infinite headaches. The business mechanism to try and solve this needs to be simple and relatively clear and should align with the science. The general population doesn't have the time or capabilities to understand the complexities. I am not saying hide the complexity - I am just saying don't have it in the forefront of the policy decisions - and don't constantly change the regulatory mechanism unless it is grossly misaligned with the science. I am glad you think the average person has the same capability to understand the problems and has taken environmental science engineering programs - I feel much better about that.
ncmncm 5y ago
This is very enlightening! Key fact is how much methane is already there when your gout entered matters a great deal, because its rate of clearance is limited by how much hydroxyl radicals it can muster.
Robotbeat 5y ago
Another question I had: what does methane become once it breaks down? It becomes CO2 (a relatively minor greenhouse gas per unit weight, but long-lived) and H2O, right? H2O is no big problem in the lower troposphere. It just rains out. But in the stratosphere… it can stick around for much longer and impact the climate. How much does this matter for methane? I would imagine methane floats up pretty high into the upper reaches of the atmosphere. Does it keep going? What stops it from getting to the thermosphere and (ultimately) exosphere?
- masklinn 5y ago
  > It becomes CO2 (a relatively minor greenhouse gas per unit weight, but long-lived) Although it should be noted that 1 tonne methane decays into around 2.5 tonnes of CO2 (I don't remember the exact number but it's around that) and GWP is measured by weight. So even after it's decayed, methane has a higher GWP than CO2. Which is why its GWP remains much higher than CO2 even over extremely long periods: methane has a GWP of ~80 over 20 years, ~30 over 100 years, but is still around 7 over 500 years, despite a lifetime of only 12 years.
  - Robotbeat 5y ago
    What about the H2O?
  - snewman 5y ago
    [OP here] thank you! I see those ratios for 20 vs. 100 years everywhere, but I've never been able to put together a mental model that explains them. You've supplied the missing piece.
a_c 5y ago
> never trust a number One pet peeve of me is the water consumption of everything. Take milk production for example, it disregards so many things, local climate, soil conditions, ecology of having cow on land, biodiversity and so on. Somehow milk production boils down to a single number and is compared with e.g. almond milk. Almond milk uses less water hence good. At least we are way over the age of line of code..
- colechristensen 5y ago
  Yup. In Iowa we put porous pipes in the ground to drain rain into the rivers faster because otherwise about half the state would have standing water on the surface. Water consumption of Iowa cows does not matter at all, water consumption of a lot of cows doesn't matter at all. There is very little irrigation in Iowa. There are places where water is a limiting factor, and places where it isn't.
cwkoss 5y ago
If I have a compost pile that's producing methane, is igniting that methane to convert it all into CO2 (regardless of getting any utility from that energy) effectively "net carbon negative" because CO2 has much less climate effect than methane? Kind of weird to think about how burning methane without capturing the energy could be better for the planet that letting it leak into the atmosphere naturally.
- mikepurvis 5y ago
  I believe the answer is yes, but I imagine it would be far too diffuse to actually achieve ignition. Same issue applies to various schemes for putting a pilot light at cow's butts to eliminate the "cow fart emissions" issues. (Quite apart from the fact that it's belches not farts that are the issue anyway, so the pilot light would be at the wrong end...)
  - wardedVibe 5y ago
    Wait, are you telling me that we need fire breathing cows for the good of the environment?
- gruez 5y ago
  Yep. It's also the same idea why we have gas flares on oil wells. It might look like it's oil companies setting stuff on fire for no reason, but it's better than just letting it leak.
  - asciimike 5y ago
    Throwing that natural gas through a generator and an exhaust system is even better (more "net negative"). Compared to flaring, you can achieve a ~98% methane reduction and a ~60% CO2e reduction (source: https://www.crusoeenergy.com/digital-flare-mitigation https://www.crusoeenergy.com/digital-flare-mitigation). Disclosure: I work for Crusoe Energy, who's goal is to eliminate routine flaring and align the future of computing with the future of the climate. We colocate data centers serving crypto miners and a high performance GPU cloud (crusoecloud.com). Our GPUs are indeed "carbon reducing", offsetting the emissions of a car over the course of a year.
sandworm101 5y ago
>> This has to be a typo, but it’s yet another reminder that – say it with me – you can never trust a number. No. Never trust an answer to an overly-simplified question. Asking for the lifetime of atmospheric methane is like asking what temperature water boils at. When faced with an overly-simplistic question an intelligent respondent will generally make all sorts of assumptions. I assume he means at sea level. I assume he means on planet earth. I assume he means normal not-heavy water. Answer: 100c. This isn't about trusting answers in the form of simple numbers. Ask an overly-simple question and expect an overly-simple answer. The fault is with the asker.
- s1artibartfast 5y ago
  It is clearly both. The correct answer to an overly simple question is that it depends. If someone is stating an answer, but leaving off the assumptions, they are doing a disservice
dexwiz 5y ago
Half lives are a poor term for this; you are really looking for reaction rates, which are dynamic systems. Methane doesn't just disappear, it reacts with something else. A radioactive isotope's decay is relatively self contained, so the half life terminology holds. A microgram or a kilogram of U-235 will decay at about the same rate, making half life a useful number. Methane reacts with OH, which is sourced from different places. Upper levels of the atmosphere get more UV light, which produces all sorts of radicals to react with. But there are also biological and geological sources for radicals which also contribute to reactions. Sum these reactions together and you get something that can be approximated with a half life, but this assumes constant input of reactants. As we increase our output of Methane this changes the reaction rates in the atmosphere and that half life number changes.
- ComputerGuru 5y ago
  AP Chemistry: the year I took it was the first (only?) year a free response question didn’t feature reaction rates. I learned my lesson on the risks of studying to the historic exam contents!
- gertlex 5y ago
  As someone whose academic background was in nuclear stuff (but ~10 years ago alas), I had fun read of this article for the considerations like "ohh, a 'half life' with multiple decay modes of varying weights depending on the environment, etc. Gives an itch to dive back into numbers wrangling/plotting! I agree that an accurate description of the (atmospheric in this case) systems over time definitely needs reaction rates, but similar considerations are also needed with nuclear radiation in a lot of situations too: e.g. the overall uhh radioactivity (for lack of recollection of precise terms) is a function of the chain of decay products, which are also often radioactive. That is to say, you might start with half-lives in calculations for dose estimation as a function of time, but you quickly get into more complex things. Also in the nuclear realm, add sources, like a running reactor, or a fresh set of fuel rods, and you get some very interesting effects over time! I think this article was a fair example walkthrough of how things quickly get more complex than the numbers (mis)quoted to the public. I was hoping it would go further, even.
philipov 5y ago
I finally understand methane lifeforms...
agluszak 5y ago
The next step would be understanding Rust lifetimes ;)
rob_c 5y ago
As a self professed what? Ive read pop-sci books with more graphs and equations over breakfast. Why is there this celebration of mediocrity in dealing with equations and instead citing percentages.

213 points by gk1 5y ago

Don't forget about those deep ocean Methane Clathrates !

tl;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.

thatcherc 5y ago
> 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!
- rocqua 5y ago
  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.
  - washadjeffmad 5y ago
    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.
  - scratcheee 5y ago
    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.
  - mudita 5y ago
    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-materials-may-help-curb-methane-emissions https://news.mit.edu/2022/dirt-cheap-solution-common-clay-ma...
amateurICEguy 5y ago
(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?
- twic 5y ago
  FWIW, and this is a rather minor and pedantic point, these are hydroxyl radicals, not hydroxide ions, so it's: H2O + γ -> OH• + H• Rather than: H2O + γ -> OH- + H+ Oh, and whichever way, H2O splits into OH and H, not OH and O, but i assume that was a typo!
  - robocat 5y ago
    > OH• https://en.wikipedia.org/wiki/Hydroxyl_radical https://en.wikipedia.org/wiki/Hydroxyl_radical “Notation: The unpaired electron of the hydroxyl radical is officially represented by a middle dot, •, beside the O.” Note that article uses a superscripted dot <sup>•</sup>OH, and the dot is usually prefixed in the article (presumably so as to put the dot next to the O that doesn’t have a full shell?). However the article sometimes suffixes the dot, to put it beside the R organic radical. Weird.

dr_dshiv 5y ago

So, 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?

tejohnso 5y ago
> 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.
- dr_dshiv 5y ago
  Here is a source explaining why the CO2 produced by methane isn’t counted in estimates of global warming potential. It seems to come down to the different calculations required for anthropogenic sources. https://ghginstitute.org/2010/07/13/what-is-different-about-methane-ch4-emissions-the-forgotten-co2-in-ghg-emissions-accounting/ https://ghginstitute.org/2010/07/13/what-is-different-about-...
alexose 5y ago

bricemo 5y ago

Beyond methane and climate change, this is a lovely step through of simply grappling with a new concept to understand it, one site/paper at a time. I wish I could teach my parents how to do this, they never get beyond the first page

photochemsyn 5y ago

Additional source describing the difference between CH4 and CO2 in the atmosphere: > "Methane makes up just 0.00018 percent of the atmosphere, compared to 0.039 percent for carbon dioxide. (CO2 is roughly 200 times more abundant.) Yet scientists attribute about one-sixth of recent global warming to methane emissions; what methane lacks in volume it makes up for in potency. Over a 20-year period, one ton of methane has a global warming potential that is 84 to 87 times greater than carbon dioxide. Over a century, that warming potential is 28 to 36 times greater. The difference occurs because methane is mostly scrubbed out of the air by chemical reactions within about ten years, while carbon dioxide persists in the atmosphere for much longer than a century." https://earthobservatory.nasa.gov/features/MethaneMatters https://earthobservatory.nasa.gov/features/MethaneMatters A big uncertainty is the future of permafrost and shallow marine sediments, which store carbon in various forms. Some scenarios are, well, not good: https://climatemodeling.science.energy.gov/presentations/impact-methane-clathrate-emissions-earth-system https://climatemodeling.science.energy.gov/presentations/imp... > "Our simulations include a plausible release from clathrates in the Arctic that increases global methane emissions by 22%, as well as a scenario with 10 times those clathrate emissions. The CESM model includes a fully interactive physical ocean... The results indicate that such Arctic clathrate emissions (1) increase global methane concentrations by an average of 38%, non-uniformly; (2) increase surface ozone concentrations by around 10% globally, and even more in polluted regions; (3) increase methane lifetime by 13% ..." It's kind of like defrosting a freezer full of 25,000 year old fish guts...

paultgriffiths 5y ago

Very interesting, and a great description of methane self-feedback. The perturbation lifetime analysis - the idea that the time constant of the atmospheric response to methane is longer than the time constant of the reaction that removes methane - comes from a beautiful paper by Michael Prather that may be of interest to anyone with some linear algebra. See https://unfccc.int/files/meetings/workshops/other_meetings/application/pdf/prather1994.pdf https://unfccc.int/files/meetings/workshops/other_meetings/a....

boringg 5y ago

It's this level of understanding that can't be pushed out to the general population. It is far too complicated for people to grasp. Add on to these complexities is that if we are trying to price carbon - the impacts change with the concentrations in the atmosphere. The market needs to be dumbed down to simplistic values (which thankfully they have) so that we have a sense on where to target and incentivize change for policy makers otherwise it is far to easy for mud-rakers to try and undo meaningful work/change in our policy/business arenas. Abstract away the complications. Great piece.

nverno 5y ago
I think it is the dumbing down that makes it easier for mud-rakers. People know it's complicated anyway, and the average person can grasp complicated things as well as you.
- deleted 5y ago
  [deleted]
- Enginerrrd 5y ago
  As an environmental engineer that deals with the interface between the public and policy makers, I think I'm inclined to agree with you. The public IS dumb, but every time they try to dumb down the principles they regulate on, it always comes at the detriment of the environment and the 'little guy'. It's almost always better to delegate policy to smart qualified people with correctly aligned interests. Getting that latter part right is hard, but that is the job of a competent public official.
  - boringg 5y ago
    It's a difficult place to be - damned if you do and damned if you don't.
- boringg 5y ago
  I disagree. There is an inherent risk that dumbing down or abstracting away the complexities of the science to have an appropriate discourse on appropriate policy action creates blowback but trying to create a system that accounts for the complexities of the science would just cause infinite headaches. The business mechanism to try and solve this needs to be simple and relatively clear and should align with the science. The general population doesn't have the time or capabilities to understand the complexities. I am not saying hide the complexity - I am just saying don't have it in the forefront of the policy decisions - and don't constantly change the regulatory mechanism unless it is grossly misaligned with the science. I am glad you think the average person has the same capability to understand the problems and has taken environmental science engineering programs - I feel much better about that.

ncmncm 5y ago

This is very enlightening! Key fact is how much methane is already there when your gout entered matters a great deal, because its rate of clearance is limited by how much hydroxyl radicals it can muster.

Robotbeat 5y ago

Another question I had: what does methane become once it breaks down? It becomes CO2 (a relatively minor greenhouse gas per unit weight, but long-lived) and H2O, right? H2O is no big problem in the lower troposphere. It just rains out. But in the stratosphere… it can stick around for much longer and impact the climate. How much does this matter for methane? I would imagine methane floats up pretty high into the upper reaches of the atmosphere. Does it keep going? What stops it from getting to the thermosphere and (ultimately) exosphere?

masklinn 5y ago
> It becomes CO2 (a relatively minor greenhouse gas per unit weight, but long-lived) Although it should be noted that 1 tonne methane decays into around 2.5 tonnes of CO2 (I don't remember the exact number but it's around that) and GWP is measured by weight. So even after it's decayed, methane has a higher GWP than CO2. Which is why its GWP remains much higher than CO2 even over extremely long periods: methane has a GWP of ~80 over 20 years, ~30 over 100 years, but is still around 7 over 500 years, despite a lifetime of only 12 years.
- Robotbeat 5y ago
  What about the H2O?
- snewman 5y ago
  [OP here] thank you! I see those ratios for 20 vs. 100 years everywhere, but I've never been able to put together a mental model that explains them. You've supplied the missing piece.

a_c 5y ago

> never trust a number One pet peeve of me is the water consumption of everything. Take milk production for example, it disregards so many things, local climate, soil conditions, ecology of having cow on land, biodiversity and so on. Somehow milk production boils down to a single number and is compared with e.g. almond milk. Almond milk uses less water hence good. At least we are way over the age of line of code..

colechristensen 5y ago
Yup. In Iowa we put porous pipes in the ground to drain rain into the rivers faster because otherwise about half the state would have standing water on the surface. Water consumption of Iowa cows does not matter at all, water consumption of a lot of cows doesn't matter at all. There is very little irrigation in Iowa. There are places where water is a limiting factor, and places where it isn't.

cwkoss 5y ago

If I have a compost pile that's producing methane, is igniting that methane to convert it all into CO2 (regardless of getting any utility from that energy) effectively "net carbon negative" because CO2 has much less climate effect than methane? Kind of weird to think about how burning methane without capturing the energy could be better for the planet that letting it leak into the atmosphere naturally.

mikepurvis 5y ago
I believe the answer is yes, but I imagine it would be far too diffuse to actually achieve ignition. Same issue applies to various schemes for putting a pilot light at cow's butts to eliminate the "cow fart emissions" issues. (Quite apart from the fact that it's belches not farts that are the issue anyway, so the pilot light would be at the wrong end...)
- wardedVibe 5y ago
  Wait, are you telling me that we need fire breathing cows for the good of the environment?
gruez 5y ago
Yep. It's also the same idea why we have gas flares on oil wells. It might look like it's oil companies setting stuff on fire for no reason, but it's better than just letting it leak.
- asciimike 5y ago
  Throwing that natural gas through a generator and an exhaust system is even better (more "net negative"). Compared to flaring, you can achieve a ~98% methane reduction and a ~60% CO2e reduction (source: https://www.crusoeenergy.com/digital-flare-mitigation https://www.crusoeenergy.com/digital-flare-mitigation). Disclosure: I work for Crusoe Energy, who's goal is to eliminate routine flaring and align the future of computing with the future of the climate. We colocate data centers serving crypto miners and a high performance GPU cloud (crusoecloud.com). Our GPUs are indeed "carbon reducing", offsetting the emissions of a car over the course of a year.

sandworm101 5y ago

>> This has to be a typo, but it’s yet another reminder that – say it with me – you can never trust a number. No. Never trust an answer to an overly-simplified question. Asking for the lifetime of atmospheric methane is like asking what temperature water boils at. When faced with an overly-simplistic question an intelligent respondent will generally make all sorts of assumptions. I assume he means at sea level. I assume he means on planet earth. I assume he means normal not-heavy water. Answer: 100c. This isn't about trusting answers in the form of simple numbers. Ask an overly-simple question and expect an overly-simple answer. The fault is with the asker.

s1artibartfast 5y ago
It is clearly both. The correct answer to an overly simple question is that it depends. If someone is stating an answer, but leaving off the assumptions, they are doing a disservice

dexwiz 5y ago

Half lives are a poor term for this; you are really looking for reaction rates, which are dynamic systems. Methane doesn't just disappear, it reacts with something else. A radioactive isotope's decay is relatively self contained, so the half life terminology holds. A microgram or a kilogram of U-235 will decay at about the same rate, making half life a useful number. Methane reacts with OH, which is sourced from different places. Upper levels of the atmosphere get more UV light, which produces all sorts of radicals to react with. But there are also biological and geological sources for radicals which also contribute to reactions. Sum these reactions together and you get something that can be approximated with a half life, but this assumes constant input of reactants. As we increase our output of Methane this changes the reaction rates in the atmosphere and that half life number changes.

ComputerGuru 5y ago
AP Chemistry: the year I took it was the first (only?) year a free response question didn’t feature reaction rates. I learned my lesson on the risks of studying to the historic exam contents!
gertlex 5y ago
As someone whose academic background was in nuclear stuff (but ~10 years ago alas), I had fun read of this article for the considerations like "ohh, a 'half life' with multiple decay modes of varying weights depending on the environment, etc. Gives an itch to dive back into numbers wrangling/plotting! I agree that an accurate description of the (atmospheric in this case) systems over time definitely needs reaction rates, but similar considerations are also needed with nuclear radiation in a lot of situations too: e.g. the overall uhh radioactivity (for lack of recollection of precise terms) is a function of the chain of decay products, which are also often radioactive. That is to say, you might start with half-lives in calculations for dose estimation as a function of time, but you quickly get into more complex things. Also in the nuclear realm, add sources, like a running reactor, or a fresh set of fuel rods, and you get some very interesting effects over time! I think this article was a fair example walkthrough of how things quickly get more complex than the numbers (mis)quoted to the public. I was hoping it would go further, even.

philipov 5y ago

I finally understand methane lifeforms...

agluszak 5y ago

The next step would be understanding Rust lifetimes ;)

rob_c 5y ago

As a self professed what? Ive read pop-sci books with more graphs and equations over breakfast. Why is there this celebration of mediocrity in dealing with equations and instead citing percentages.