[HN Gopher] I finally understand methane lifetimes ___________________________________________________________________ I finally understand methane lifetimes Author : gk1 Score : 190 points Date : 2022-04-29 12:32 UTC (10 hours ago) (HTM) web link (climateer.substack.com) (TXT) w3m dump (climateer.substack.com) | boringg wrote: | 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. | photochemsyn wrote: | I don't think it's that complicated. Start with water vapor - | moisture evaporates from the ocean, lakes, soil, vegetation. On | average such a water molecule stays in the atmosphere for 4-10 | days - because water condenses as rain, unlike methane or | carbon dioxide. Water vapor increase accounts for about 2/3 of | the immediate global warming effect, but is controlled by | temperature, which is in turn controlled by the CO2 and CH4 in | the atmosphere. Hence we can think of water vapor in the | atmosphere as a _feedback_ to the CO2 /CH4 _forcing_. | | This is not too difficult for people to understand. The fact | that methane is a reactive gas, i.e. CH4 + O2 -> CO2 over time | (OH just being an intermediate), means it gets converted to | CO2, accounting for the relatively short 10-year lifetime. CO2 | + OH/O2 does nothing, so we can expect a longer lifetime. The | notion that CO2 lifetime in the atmosphere is 100 years is | perhaps a bit more complicated, as it involves ocean uptake and | things like that, but it's all fairly straightforward. | | The gas/oil/coal sector might want people to believe that | passing gas in a closed room won't eventually create a stink, | but it's the same general concept. | alar44 wrote: | boringg wrote: | I agree I don't think it's that complicated but when you have | a regulatory industry surrounding complex science with | politicians weighing in it can get very tricky. I refer to | climate deniers/paid advocacy groups and mud rakers who | constantly try and trip up progress by trying to bring sow | doubt through poking holes in the argument or nitpicking | small issues. | s1artibartfast wrote: | >I don't think it's that complicated | | The complicated part that I have spent many hours trying to | understand is how more CO2 increases the greenhouse effect if | the the frequencies it absorbs are already 100% absorbed. | | If current CO2 PPM absorbs 100% of the IR it can interact | with, why does X+1 PPM have positive forcing? The feedback | loop is already maxed out? | | If I shine a flashlight at a concrete wall, it doesn't matter | if I make the wall thicker. | lstodd wrote: | You forgot the albedo effect of the clouds. On both sides - | top and bottom. This has not ever been modelled to my | knowledge. And it is very complicated. | quantum_magpie wrote: | Albedo is included in every single atmospheric model. | nverno wrote: | 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] | Enginerrrd wrote: | 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 wrote: | It's a difficult place to be - damned if you do and damned | if you don't. | boringg wrote: | 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. | the8472 wrote: | You can't push it out in a single news blurb. But if it were | covered as some math/physics/chemistry sections building on | each other in secondary education it should be manageable. | Especially if you already covered exponential decays. Add the | secondary effect of the exponential decay parameter varying | based on concentration. | cwkoss wrote: | 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 wrote: | 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 wrote: | Wait, are you telling me that we need fire breathing cows for | the good of the environment? | gruez wrote: | 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 wrote: | 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). | | 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. | [deleted] | s1artibartfast wrote: | The same is true for a lot of chemistry. There are tons of | compounds that are poisonous, but if you break down the | molecule, it is perfectly safe to eat. | bricemo wrote: | 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 wrote: | 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 | | 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/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... | ncmncm wrote: | 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. | a_c wrote: | > 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 wrote: | 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. | sandworm101 wrote: | >> 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 wrote: | 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 | dr_dshiv wrote: | 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? | ComputerGuru wrote: | The short lifespan of an OH radical isn't an issue if it's | deployed at the site of emission (a la scrubbers). You then | don't need them to last long enough to randomly bump into | methane particles in the wild as you're inducing them in a | high-methane concentration environment where you expect them to | react before they react with something else and break down. | | That's the moral of the story for all climate control: don't | produce bad stuff, if you have to try to get rid of it as close | as possible (temporally and spatially) to the source because | once it's diluted in the atmosphere it becomes insanely more | difficult. | | Global CO2 levels are at 450 parts per _million_ meaning you | need to actively filter 2,222 parts of air to get to one measly | CO2 molecule _in the wild_. It's horrible inefficient | (expensive and slow). But if you don't produce the CO2 or if | you tackle it right then and there at the site of production | where it is at much higher concentrations, you still have a | chance. | thaumasiotes wrote: | I remember someone pointing out that (1) there is a very | large amount of advocacy based around going to the Great | Pacific Garbage Patch and harvesting microplastic particles | there; and (2) this is a colossally stupid idea, because | there is almost no plastic in the Great Pacific Garbage | Patch. It's a a part of the ocean where the level of plastic | is higher than usual. But it's still a part of the ocean. | | If you want to filter plastic out of the ocean, you want to | filter it out of the input stream, where it's concentrated, | not out of the end product of diluting the input stream with | the entire ocean. | | Interestingly, the wikipedia article on the Patch is | headlined by a disclaiming of a very similar mistake: | | > Despite the common public perception of the patch existing | as giant islands of floating garbage, its low density (4 | particles per cubic metre (3.1/cu yd)) prevents detection by | satellite imagery, or even by casual boaters or divers in the | area. | | https://en.wikipedia.org/wiki/Great_Pacific_garbage_patch | metacritic12 wrote: | > There is limited OH in the atmosphere. As a result, more | methane "uses up" the OH. | | > So, why not produce a bunch of OH? Because OH has a half life | of less than a second. Hmm. | | These two statements seem to contradict? If the chemokinetics | of OH generation is less than a second, then how can it be used | up in the atmosphere? | | Assuming the <1 second kinetic is correct, there must be a | dynamic equilibrium producing it in the atmosphere to begin | with. In such a case OH is not truly being used up in any real | sense. It's whatever that generates OH is being used up, and | that can be artificially boosted. | conradev wrote: | One limiting factor in generating OH is specific wavelengths | of light, which is harder to artificially boost | dr_dshiv wrote: | Laser beams. We can only hope that this whole solution is | dependent on laser beams :) | s1artibartfast wrote: | "consumed" is better than "used up". | | In that <1 second, the OH can react with methane or CO. The | more CO in the atmosphere, the more likely it will find the | OH before the methane. | | It is like throwing breadcrumbs to ducks and geese. The more | ducks in the pond, the less crumbs the geese will get. | quantum_magpie wrote: | It's because that statement is incredibly wrong. Methane | concentrations in atmosphere are 8 orders of magnitude higher | than OH. More methane in the atmosphere has exactly 0 effect | on OH. And you can't inject OH into atmosphere either because | it will react with pretty much anything it comes in contact | with. | s1artibartfast wrote: | In this case, annual reaction mass of OH is more important | than the concentration at any given time. The concentration | of any highly reactive molecule will be very low, but that | doesn't tell you how much was created or consumed. | | Methane levels don't impact OH levels (it is always | consumed immediately). OH generation levels can impact | methane levels. CO levels can compete with methane for OH | as is it generated. | isoprophlex wrote: | Look at it this way: there's a finite amount of OH radicals | being produced each interval of time, which reacts with some | CH4 and disappears in the reaction. | | You are correct that OH radicals regenerate, but more methane | => "breakdown capacity" becomes overwhelmed. | | This is known as zeroth order kinetics, similar to alcohol | metabolism. Drinking 2 beers = 3 hours until sobriety; 4 | beers = 6 hours. Your liver has a fixed capacity, so drinking | twice as much doesn't double the metabolic rate. | | I'll add that you're also entirely correct: if there's some | long lived chemical that catalyzes OH formation, sending that | up instead might be a good remedy IMO. If there's no | collateral toxicity... | quantum_magpie wrote: | There is no such thing as zero-order kinetics in | atmospheric chemistry. | zackees wrote: | alexose wrote: | There's a group that is advocating for spraying an Iron Salt | Aerosol into the atmosphere, which apparently catalyzes the | natural decomposition process. I haven't done a deep dive into | the subject, but on the surface it seems pretty compelling. | | https://ironsaltaerosol.com/home/isa_summary | quantum_magpie wrote: | Well they haven't tested any of their assumptions in the | field and their atmospheric chemistry cycle diagram has some | bullshit reaction mechanisms so it is pretty much shit. | | Also the following statement surprisingly lacks any mention | of anything related to atmospheric or earth scientists: | | >We seek funding for a world-first trial in Australian waters | under scientific supervision, in cooperation with the marine | biology community and with industries including insurance, | fishing, tourism, energy and shipping. | dr_dshiv wrote: | How much money is worth "wasting" to investigate new | possible solutions to global warming? | | If you look at the "official" plans, they all rely on the | emergence of magical new technologies. So we'd better start | testing even the less promising approaches. Shotgun | strategies are needed. | | Of course, at the moment, many are seeking to _ban research | science_ in this area because it is viewed as morally | dangerous [1]. | | [1] https://climateandcapitalism.com/2022/01/17/climate- | scientis... | quantum_magpie wrote: | In this case, I think people want to ban large-scale | deployments of untested, unvalidated technologies with no | definitive positive effect and a non-negligible | probability of disastrous consequences. | | I myself am an atmospheric chemist and no one has banned | me from doing scientic research. | dr_dshiv wrote: | Read their letter and paper. They don't want to ban large | scale deployments. They want to ban _any_ deployments, | even for small-scale research purposes. This will ensure | that all unvalidated technologies remain untested. That's | unfortunate because we all know we can't decarbonize in | time. We need other braking mechanisms and we should be | pretty open to experimentation. | | If no one is upset with your particular atmospheric | research, maybe you aren't ambitious enough. Just | kidding-- I'd love to know what you are working on. | beders wrote: | what could possibly go wrong? Let's put iron chloride where | it doesn't belong, outside of our control. | | Haven't we done enough harm yet? | s1artibartfast wrote: | you could say the same about anything. Installing solar or | wind power isn't natural part of the environment, and | "something" could go wrong, better not do that either. | rootusrootus wrote: | Seems like we've come far enough to understand that doing | nothing and conserving our way out of this problem isn't | viable. The time for engineering is upon us. | jxramos wrote: | it's interesting folks have interpreted this as a blocking | call to effectively do nothing in the face of such | uncertainty. To me it was an invitation to begin to engage | in second order thinking. | tejohnso wrote: | > 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 wrote: | 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-... | paultgriffiths wrote: | 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/a.... | Robotbeat wrote: | 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 wrote: | > 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 wrote: | What about the H2O? | snewman wrote: | [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. | dexwiz wrote: | 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 wrote: | 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! | Melatonic wrote: | Don't forget about those deep ocean Methane Clathrates ! | rob_c wrote: | 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. | philipov wrote: | I finally understand methane _lifeforms_... | wrycoder wrote: | 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._ | amateurICEguy wrote: | (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 wrote: | FWIW, and this is a rather minor and pedantic point, these | are hydroxyl radicals, not hydroxide ions, so it's: | | H2O + g -> OH* + H* | | Rather than: | | H2O + g -> OH- + H+ | | Oh, and whichever way, H2O splits into OH and H, not OH and | O, but i assume that was a typo! | robocat wrote: | > OH* | | 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. | thatcherc wrote: | > 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 wrote: | 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. | scratcheee wrote: | 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 wrote: | 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... | washadjeffmad wrote: | 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. | agluszak wrote: | The next step would be understanding Rust lifetimes ;) ___________________________________________________________________ (page generated 2022-04-29 23:00 UTC)