8 ms·
UVB radiation was the Devonian-Carboniferous extinction kill mechanism
- 01100011 6y agoHopefully this time we'll be able to geoengineer our way out of it. I would think pumping out tons of ozone is significantly easier than removing atmospheric CO2 or, you know, burning less carbon(how absurd, right?).
- ben_w 6y agoWell, there is less ozone in total than CO2 produced per year, but ozone is harmful at ground level: https://ozonewatch.gsfc.nasa.gov/facts/ozone.html https://ozonewatch.gsfc.nasa.gov/facts/ozone.html
- klyrs 6y agoElectric sparks make ozone, so clearly what we need is nuclear powered tesla-coil zeppelins to produce it in the upper atmosphere.
- nxpnsv 6y agoNot sure it works, but I would pay to see one...
- vanderZwan 6y agoDon't ion drives have ozone as a side-effect? Balloons with solar-powered ion drives might do the trick then - they don't even need to be lighter than air, the ion drive should give it enough thrust https://www.youtube.com/watch?v=boB6qu5dcCw https://www.youtube.com/watch?v=boB6qu5dcCw https://www.youtube.com/watch?v=a9yYu-ZM1S0 https://www.youtube.com/watch?v=a9yYu-ZM1S0
- Gravityloss 6y agoBut you have to avoid generating nitrogen compounds... And if there's water vapor, also hydrogen to think about. But a solar powered ozone generating ion wind propelled plane perpetually flying high up there certainly sounds cool. It could also act as a communications relay.
- vanderZwan 6y ago> But you have to avoid generating nitrogen compounds What if we reverse the polarity on the main deflector dish.. I mean emitter wire? > The effect is not directly dependent on electrical polarity, as the ions may be positively or negatively charged. Reversing the polarity of the electrodes does not alter the direction of motion, as it also reverses the polarity of the ions to match. Thrust is produced in the same direction, either way. For positive emitter polarity, nitrogen ions are the main charge carriers, while for negative polarity, oxygen ions are the main carriers and ozone production is higher.[citation needed] https://en.wikipedia.org/wiki/Ion-propelled_aircraft https://en.wikipedia.org/wiki/Ion-propelled_aircraft (also, I just used "reverse the polarity" unironically. I can check that off my bucket list)
- klyrs 6y ago> Don't ion drives have ozone as a side-effect? Sure, if you wanna take my suggestion of nuclear-powered shock-zeppelins seriously... (loving the conversation my ridiculous idea inspired)
- kortex 6y agoActually spark gaps are less efficient than corona discharge. Usually ozone generator just apply high electric field to plates and run air/oxygen through it. Now I'm curious what the energy efficiency of this process is. I wonder if the rarefaction at that altitude makes it easier or more challenging.
- adrianN 6y agoAnybody can make Ozone, but how do you propose getting it high enough in the atmosphere?
- airstrike 6y agoQuick, get Elon on the phone!
- jojobas 6y ago1) Advance solar cell technology a little bit more 2) Make a Solar Impulse kind of planes that basically deposit excess power in sparkgaps 3) Ozone I suspect the ozone layer is not our biggest problem with the warming though.
- namibj 6y agoOh, we can already build planes that use high-efficiency propellers (with efficient and lightweight gear-less axial flux motors) and soar above the clouds 24/7, using height instead of batteries and ultra-light back-ground solar cells laminated into a giant flying wing (or at least much more wing than fuselage, because the motors should be distributed to reduce demands on wing stiffness). A weight of less than 2.5kg/m^2 in the wing should be feasible with large, monolithic carbon fiber sections, joined by narrow engine segments. Overall it should be possible to stay below a wing loading of 5kg/m^2, so a 100m span, 1m chord 500kg plane gets about 18h out of 10km height, see https://www.rcgroups.com/forums/showthread.php?2601411-Is-wing-loading-what-determines-the-minimum-sink-rate-of-a-glider https://www.rcgroups.com/forums/showthread.php?2601411-Is-wi... .
- rrmm 6y ago> I would think pumping out tons of ozone is significantly easier than removing atmospheric CO2 or, you know, burning less carbon(how absurd, right?). That reminds me of the Simpsons episode where they bring in a serious of increasingly more absurd animals to deal with a small invasive species they find. https://youtu.be/3f5viRoaZNw?t=87 https://youtu.be/3f5viRoaZNw?t=87
- dTal 6y ago"...thus solving the problem once and for all!" "But-" "ONCE AND FOR ALL!" https://www.youtube.com/watch?v=0SYpUSjSgFg https://www.youtube.com/watch?v=0SYpUSjSgFg
- lvs 6y agoWe don't know who struck first, us or them. But we do know it was us who scorched the sky.
- rrmm 6y agoIn our defense we thought it would stop the bullet time camera effects.
- labster 6y ago> Hence, ozone loss during rapid warming is an inherent Earth system process with the unavoidable conclusion that we should be alert for such an eventuality in the future warming world. Did not know this worrisome hypothesis. The idea that a warming world could inject more reactive material into the stratosphere via convective storms seems reasonable. Thanks a lot for one more reason not to sleep tonight.
- rrmm 6y agoI know right. "Hey I see you like worrying about stuff...well, how about these apples!" Scientists really need to learn how to keep it to themselves for like a year or two. /s
- philipov 6y agoCan't do that when their grant money and the possibility of further research depends on being a prolific marketer as well as a great researcher.
- jbay808 6y agoThis hypothesis about the end Permian mass extinction is also quite scary: http://burro.case.edu/Academics/USNA229/impactfromthedeep.pdf http://burro.case.edu/Academics/USNA229/impactfromthedeep.pd...
- ChuckMcM 6y agoHence the larger conversation around becoming multi-planetary as a species being a survival mechanism.
- sandworm101 6y agoFixing the ozone layer is far easier than moving a substantial of the earth's population off-planet. The total amount of gas is not extreme, which makes it so delicate but also means that we may be able to artificially manage it.
- rrmm 6y agoOh hey, another bad thing to worry about happening in 2020. But it's a cool paper. It would be interesting to see if they can find more instances of this sort of damage over various, widely space geographic areas. And especially in other species/other external signs of UV damage. Even though they do analysis to try to eliminate other possible explanations, I'm not sure I'm super on board with immediately accepting the UV/ozone explanation whole sale. I always like to see bets hedged with "lends further evidence to support...." language. I'd also love to hear from anyone with domain knowledge that might be able to add their perspective on the paper.
- londons_explore 6y agoI have searched for, but been unable to find, a chart of estimated UV levels at ground level over the past few hundred years. I'm interested in it because suntans seem so much worse now than in the past, where people didn't have access to suncream, yet still spent lots of time outside. "I got used to it by spending my whole life outside" doesn't seem to fully explain it.
- rrmm 6y agoI don't know if they even have that data for that length of time. You might find some info in literature regarding the difference in UV exposure in areas under the ozone hole vs areas of more normal exposure. As an aside, don't get misled by nutters talking about ground level UVC levels. They don't know what they're talking about and are citing people who don't know how to use their UV-C meters (which are sensitive at wavelengths other than UVC and therefore require extensive filtering). Further edit: I should mention total solar irradiance has remained relatively consistent over time (and continues to). I bring up these things because I've talked to some nutty people about this stuff in the past and those are common stepping off points into la-la land.
- kaybe 6y ago>I should mention total solar irradiance has remained relatively consistent over time (and continues to). It should be noted that the 11-year solar cycle is much stronger in the shorter wavelengths, especially below 200nm. Since that is absorbed in the ozone layer there is a change of up to 2K max in the stratopause (~50km). It doesn't really appear to propagate down, and is rather on the level of a scientific curiosity, but still. [0] (Longer-term changes than the 11-year oscillation seem to be much lower, but this is hard to determine.) [0] https://pubs.giss.nasa.gov/abs/gr08900n.html https://pubs.giss.nasa.gov/abs/gr08900n.html To the parent post: If you want to have information about UV at ground level you can look at proxy data. [1][2][3] Of course there are some complications with that as always though, and it's not that easy to interpret. But it looks like while there is variation it is mainly along the 11-year cycle. (I can't say much about the strength of the change on ground level without further reading. It's in the low percent range on top of the atmosphere, but almost all of that will be stopped in the ozone layer.) [1] https://pubs.rsc.org/en/content/articlelanding/2009/PP/b904515e#!divAbstract https://pubs.rsc.org/en/content/articlelanding/2009/PP/b9045... [2] https://www.tandfonline.com/doi/abs/10.1080/01431160500077051 https://www.tandfonline.com/doi/abs/10.1080/0143116050007705... [3] https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1469-8137.2011.03815.x https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1469-... Considering the issue of suntans, I think looking at the clothes people wear is more relevant to the question to be honest.
- MattGaiser 6y agoI didn't see a temperature for when this might become a problem. Does anyone have that?
- rrmm 6y agohttps://science.sciencemag.org/content/337/6096/835/tab-pdf https://science.sciencemag.org/content/337/6096/835/tab-pdf That's the ref in the paper. It's a bit confusing because they're looking at chemical processes taking place at 15-20km altitude. Temps there are around -55C maybe, 200K). They plot changes for activation of the process, but I don't have enough knowledge about it to understand the implications. The bottom axis of their graph runs from 195K - 210K though so clearly it's not a big delta. They seem much more interested in the amount of water vapor at altitude. The other thing is that it seems like the process has a fairly short cycle time. By which I mean they mention changes on the order of days. When I think about ozone holes I think mainly in the context of decades. So I'm not sure how much the mention of warming and ozone loss in the OP paper was a 'hey that might be of note,' or was a more substantially linked relationship. (I kind of wonder if pole reversal/magnetic field weakening or solar events could play into the loss of ozone during the extinction in the original paper?) The paper makes this statement at the end: Last, we emphasize that because chlorine ac- tivation depends exponentially on water vapor and temperature, and in turn that the forcing of climate may well control the convective injec- tion of water into the lower stratosphere, the idea that ozone “recovery” is in sight because we have controlled chlorofluorocarbons and halon release is a potential misjudgment.
- rrmm 6y agoOk so I think the parameter you want to be looking for is the temperature (not necessarily at altitude) that results in some particular amount (ppmv) of water vapor at altitude. With the understanding that the hotter it is at altitude the worse the mechanism is for ozone.
- sneak 6y agoContext for those of you (like me) who aren't geologists and don't know of any historic extinction events other than the k-t (66 Mya): https://en.wikipedia.org/wiki/Late_Devonian_extinction https://en.wikipedia.org/wiki/Late_Devonian_extinction (376–360 Mya)
- avancemos 6y agoThis is not a high profile paper. The accompanying domain to this post is (unintentionally) misleading: the actual journal that this paper is published in is ’Science Advances’, not ’Science’ (the prestigious one). I thought there was something funny about the abstract...most abstracts in high profile journals have a much different tone.
- rrmm 6y agoGood catch. Advances I gather is their open-access journal? Not necessarily any worse I would think, but yeah not for the big impact papers.
- avancemos 6y agoIt’s a solid journal to be fair (impact factor around 12, whereas Science is 40-something).
- nabla9 6y agoBoth 'Science' and 'Nature' have prestige, but people get confused because same domains are used for multiple journals. Open access journals like Advances or Nature Communications are not that bad, but Nature Scientific Reports is horrible. It's very low impact journal with minimum review. It's intended to be place for grey literature where technical reports and scientific reports with no importance go. Unfortunately it has started to publish junk science too. Those pieces get posted into HN frequently. All that happens under nature.com that makes them seem legit.
- TheGallopedHigh 6y agoThis is not entirely true. It has a low impact, but is still reasonable. Nature Scientific Reports is still published by nature and does peer review. Granted the content is not on the level of nature itself. And junk science? Please provide links.
- nabla9 6y ago
- aaron695 6y agoSounds like total bullshit and why science is failing. Off one plant they re-write as absolute fact the story of a whole extinction? Throw in politics in the abstract so no one can question it and you have science today. And the people love it! The new entertainment for the masses.
- rrmm 6y agoIt's a single paper in a journal. This is how science works: they are putting out their hypothesis and the data and their conclusions. It doesn't mean they're 'right' (regardless of the certitude of the HN headline).
- rrmm 6y agoI think it is important to state, that this isn't some established fact. And it's not a thing that this one paper could 'establish' as fact.
- colechristensen 6y agoI'm wondering how modern species would be differently vulnerable to a similar UV challenge. The paper specifies the evidence they found and a mechanism being DNA corruption in plant spores which were very exposed – well today most of those plants (like all sorts of ferns) are extinct and replaced by flowering plants with their much hardier seeds.
- Freestyler_3 6y agoseeds or spores are they interchangeable? I thought spores are like sperm, they are needed to produce seeds... or am I wrong?
- colechristensen 6y agoNot at all interchangeable. The lifecycle of ferns is a bit exotic and familiar. It's classified as alternating between two generations, the one which produces the familiar large plant, and one that produces tiny plants. It's something like "sexual reproduction with extra steps". The fern chops its genome in half and produces spores with these haploid genetics. The spores grow into tiny plants (< 1 cm) which grow leaves and roots and then produce the sperm and/or eggs (the sperm actually swims to the egg!) which fertilized, grow into a new familiar fern. In flowering plants, seeds are the result of fertilization which happens in the plant, they're bigger, contain food, and protective shells. The living cells which carry life are hidden inside. Pollen is a bit like a spore in that it's tiny and contains haploid genes, but still I'm guessing that process of reproduction is considerably more durable to increased UV.