[HN Gopher] Eliminating contrails from flying could be cheap
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Eliminating contrails from flying could be cheap
Author : K2L8M11N2
Score : 72 points
Date : 2025-10-07 19:07 UTC (3 hours ago)
(HTM) web link (www.sustainabilitybynumbers.com)
(TXT) w3m dump (www.sustainabilitybynumbers.com)
| pavel_lishin wrote:
| I had no idea contrails actually caused that much warming,
| compared to the exhaust.
| Nzen wrote:
| Likewise. In fact, I was under the opposite impression because
| of the benefit that sulfur enriched shipping exhaust had for
| our climate [0]. It looks like these clouds are thinner and
| don't have the same impact as that, though. While I felt that
| the featured article linked to their favorite site aggressively
| (four links to contrails.org), it looks like the google site is
| legitimate [1]. I couldn't find a recent [2] paper on NoAA
| about contrails, but presumably others have studied it.
|
| [0] https://cpo.noaa.gov/the-unintended-consequences-of-
| reducing...
|
| [1] https://sites.research.google/gr/contrails/
|
| [2] https://csl.noaa.gov/news/2011/101_0714.html
| counters wrote:
| > In fact, I was under the opposite impression because of the
| benefit that sulfur enriched shipping exhaust had for our
| climate.
|
| It isn't quite accurate to state that ship tracks have/had a
| "benefit" on our climate. Their existence creates a transient
| decrease in OLR and increase in albedo. If anything, they
| simply masked some GHG-induced warming that had a much longer
| half-time, and cleaning up ship emissions has "unmasked" some
| of that hidden warming. But, again, the warming was already
| committed.
| jagged-chisel wrote:
| How much will it cost in fuel (additional miles) and time
| (flyers' lives) to reroute?
| steanne wrote:
| > The proposed detours typically result in a 1% shift (and
| again, this is only for a small percentage of flights). That
| means increasing fuel use and flight time by around 1%. So if
| your flight is three hours long, it's only adding an extra two
| minutes. For a 10-hour flight, six minutes. This seems socially
| acceptable to me; most people would barely notice.
| SoftTalker wrote:
| Airlines will certainly notice a 1% fuel cost increase
| however. But, they'll just add it to ticket prices.
| mulmen wrote:
| It's not a 1% increase in fuel costs. It's 1% of 3% (for
| 80% mitigation) to 17% (for total mitigation). That's a
| 0.03% to 0.17% increase in fuel costs.
| andrewflnr wrote:
| They'll all need to do it at once though, or people will
| just pick the cheaper flight that doesn't go around the
| contrail-forming region, basically every time.
|
| Of course it's a coordination problem. It probably needs to
| be a regulation before it will actually happen.
| actionfromafar wrote:
| 1% less fuel will not be 1% less ticket cost, but
| something much less.
| PunchyHamster wrote:
| the question is whether the contrail produces the amount of
| warming equivalent to extra fuel used, of which I'm doubtful
| jvanderbot wrote:
| The entire initiative is based on the idea that it is more
| friendly to route around contrails. I work actively in this
| area on the routing side (flightscience.ai), and can assure
| you it's actually fairly cheap climate-wise to reroute a
| flight given enough warning. If you check out their map
| (follow TFA's links), you can see that contrails are formed
| in fairly localized areas.
|
| Go to aviationweather.gov, and you can see huge boxes of
| alert areas that we _already_ have to deal with. It 's
| really just another day at the office.
| stevage wrote:
| The article addresses this in detail.
| dylan604 wrote:
| "Why aren't we doing more to eliminate contrails?"
|
| I'm just having a hard time groking that contrails are really
| that impacting. TFA just quotes a bunch of numbers, but does not
| actually discuss how the numbers were derived. Maybe I've just
| been around too many people into Chemtrails, but this just reads
| to me as an offshoot of that type of thinking.
| burkaman wrote:
| It links to this post which has a little more technical
| explanation: https://notebook.contrails.org/comparing-
| contrails-and-co2/
|
| And also this paper which is a very in-depth technical
| explanation:
| https://www.sciencedirect.com/science/article/pii/S135223102...
|
| I understand why you're reminded of chemtrails, but it is not
| crazy or conspiratorial to look at these giant lines in the sky
| and think "those things must be doing something". You can't
| then make the leap to "it's intentional and it's a biological
| weapon to control my mind and I don't need any evidence to
| believe this", but you can take the next step of looking into
| decades of research on the topic and deciding if the
| conclusions make sense to you.
| dylan604 wrote:
| Where I'm from, contrails are so small and irrelevant
| compared to the giant cumulonimbus clouds that form in the
| high heat and humidity. It's like tears in the rain in
| comparison.
| burkaman wrote:
| I don't know what to tell you, they are not irrelevant even
| if they visually look irrelevant from where you are. Small
| things can have a big impact, CO2 is only ~0.04% of the
| atmosphere (compared to the ideal level of ~0.03%) and it's
| causing us major problems.
| pixl97 wrote:
| Right there is local climate too that has different
| effects.
|
| Imagine a large city in an area that is always cloudy
| versus one in a sunny desert. They are both the same size,
| but the one in the desert is going to have an absolutely
| massive amount of evening heat release due to the urban
| heatsink effect.
| grues-dinner wrote:
| > not crazy or conspiratorial to look at these giant lines in
| the sky and think "those things must be doing something"
|
| I think more accurately it's not crazy to think they _might_
| be doing something. I could equally be convinced if
| researchers crunched the numbers and concluded they might
| seem big but they 're negligible on a global scale. In fact
| the same figure of "only 3%" of flights really have an
| effect" could easily have cut the other way.
|
| A bit like how wind turbines look huge and numerous but are
| (as yet and for the foreseeable future) completely negligible
| on the scale of global wind power.
|
| In fact plenty of times much closer to home, thinking "this
| very obvious thing _must_ be having an effect " and failing
| to verify that it actually does has screwed me over
| repeatedly in everything from bug fixing to installing
| floorboards.
| burkaman wrote:
| Sure, I meant "must be" in the colloquial sense of "I have
| a suspicion", not "I am absolutely certain". Like "it's
| 5pm, must be a lot of traffic on the highway right now". If
| traffic turned out to be light I would be mildly surprised,
| update my assumptions and move on with my life.
| grues-dinner wrote:
| Fair enough, it was pedantic. But the distinction is
| exactly where conspiracists come unstuck.
| readthenotes1 wrote:
| There's some anecdata from 9/11
|
| https://globalnews.ca/news/2934513/empty-skies-after-911-set...
| dylan604 wrote:
| The NASA image does make contrails look much larger than say
| from the ground, but even in the same image true cloud cover
| is clearly more complete than all of the contrails combined
| from the same image
| DemocracyFTW2 wrote:
| Wikipedia[1] states it very clearly:
|
| > It is considered that the largest contribution of aviation to
| climate change comes from contrails. In general, aircraft
| contrails trap outgoing longwave radiation emitted by the Earth
| and atmosphere more than they reflect incoming solar radiation,
| resulting in a net increase in radiative forcing. In 1992, this
| warming effect was estimated between 3.5 mW/m2 and 17 mW/m2. In
| 2009, its 2005 value was estimated at 12 mW/m2, based on the
| reanalysis data, climate models, and radiative transfer codes;
| with an uncertainty range of 5 to 26 mW/m2, and with a low
| level of scientific understanding. [...] Contrail cirrus may be
| air traffic's largest radiative forcing component, larger than
| all CO2 accumulated from aviation, and could triple from a 2006
| baseline to 160-180 mW/m2 by 2050 without intervention.
|
| What I can say is that even in a place with moderate air
| traffic, you get to see lots of contrails crisscrossing the sky
| on some days; in places near busy airports I hear that a
| sizable fraction of all cloud cover is due to lingering
| contrails.
|
| [1] https://en.wikipedia.org/wiki/Contrail#Impacts_on_climate
| zahlman wrote:
| > Contrail cirrus may be air traffic's largest radiative
| forcing component, larger than all CO2 accumulated from
| aviation, and could triple from a 2006 baseline to 160-180
| mW/m2 by 2050 without intervention.
|
| Okay, but how does this compare to the forcing of the overall
| anthropogenic CO2 accumulation?
| gs17 wrote:
| According to Wikipedia:
|
| > For carbon dioxide, the 50% increase (C/C0 = 1.5)
| realized as of year 2020 since 1750 corresponds to a
| cumulative radiative forcing change (delta F) of +2.17 W/m2
| bityard wrote:
| > in places near busy airports I hear that a sizable fraction
| of all cloud cover is due to lingering contrails
|
| Hmm. I don't know about that. My understanding is that
| contrails only (or mainly?) form at higher altitudes. Most of
| the traffic around a busy airport is low-altitude take-offs
| and landings. I live practically next door to a busy
| international airport and can't say I ever notice contrails,
| except for a few off in the distance around dusk.
|
| I notice a lot more contrails when I'm out in rural "flyover
| country", but that might also just be because you typically
| get to see much more of the sky when you're out in the middle
| of nowhere.
| DemocracyFTW2 wrote:
| Do you ever see this kind of sky https://www.spiegel.de/wis
| senschaft/technik/kondensstreifen-... ? That's over
| Frankfurt, Germany's busiest airport. Also from the 2020
| article (v. G. tr.):
|
| > Researchers believe that the ice clouds created by
| contrails have contributed more to the rise in global
| temperatures in recent years than all the CO2 released into
| the atmosphere since the beginning of aviation. The annual
| increase in air traffic and flight routes at ever higher
| altitudes are particularly contributing to the formation of
| ice clouds. At high altitudes, contrails can combine with
| icy cirrus clouds and thus remain in the sky for up to 18
| hours.
| roadside_picnic wrote:
| Contrails observably suppress the Diurnal Temperature Range
| (i.e. they make it cooler during the day).
|
| How could this be observed you might ask? It turns out there
| was a study done immediately after the grounding of airplanes
| during the September 11th, 2001 events to take advantage of
| this unique incidence of effectively halting all air
| transportation for a few days [0]
|
| 0.
| https://journals.ametsoc.org/view/journals/clim/17/5/1520-04...
| jvanderbot wrote:
| Well _some_ of us are doing things to eliminate contrails ...
| (Shameless self promotion of my employer)
| dylan604 wrote:
| _Some_ of us are doing things to eliminate contrails in other
| ways, like not using air travel. _Some_ of us are hermits
| that never leave the house. Can 't be more green than that.
| _Some_ of us that do wander out of the house even do so
| without using a car and avoid that bit of pollution.
|
| _Some_ of us also don 't have to worry about pulling a
| muscle reaching around trying to pat ourselves on the back
| while trying to humble brag. No shame involved either.
| huvarda wrote:
| [flagged]
| pfannkuchen wrote:
| It's funny to me that those people are all essentially a
| pessimistic flavor of homeopath (in the small quantities can
| have an effect sense).
| phoehne wrote:
| Now they're hiding the chemtrails. It's even worse!
| xnx wrote:
| Very briefly mentioned in the article, but Google worked on this
| years earlier: https://sites.research.google/gr/contrails/
|
| https://news.ycombinator.com/item?id=37060347
| imgabe wrote:
| If the incoming radiation can pass through, why can't it pass
| through on the way out?
| cvoss wrote:
| The radiation on the way in has a different frequency than on
| the way out. For example, there is UV included in sunlight. But
| black body heat at Earth's temperature radiates in infrared.
| Clouds are very opaque to infrared, and more (though not
| completely) transparent to UV.
| jcims wrote:
| This is the actual answer. The clouds aren't differentially
| reflecting sunlight into and out of the atmosphere, they are
| reflecting the black body radiation _emitted_ by the earth.
| vamin wrote:
| Because it comes in at a different frequency versus when it
| goes out. Light, including UV and visible light, hits the
| ground, then the ground gets warm and radiates in the IR, which
| can be blocked by clouds.
| burkaman wrote:
| Greenhouse gases only interact with specific wavelengths of
| light. A lot of sunlight comes in as visible or ultraviolet
| light, mostly passing through those gases. It hits the surface
| of the Earth and is absorbed and then re-emitted as infrared
| light, and a lot of that is just the right wavelength for
| greenhouse gases to interfere. Here's a good article about the
| physics of this: https://www.quantamagazine.org/the-quantum-
| mechanics-of-gree...
| justonceokay wrote:
| Single particles of radiation coming from the sun have higher
| energy than single particles radiating from the earth. Even
| though the total energy entering and leaving earth is at a near
| equilibrium.
|
| My mental model is that a bullet leaving the barrel of a gun
| has much more penetrative power than that same bullet once it
| has ricocheted off a concrete wall.
| continuational wrote:
| Basic greenhouse effect: Visible light (and ultraviolet light)
| comes in relatively unhindered. Gets absorbed by the earth and
| heats it up. The heat is emitted as infrared radiation. This
| gets absorbed by CO2 (and equivalents) and reemitted in a
| random direction. Takes a long time to reach space by chance,
| so the energy stays in the atmosphere for a while.
| tejtm wrote:
| Every wavelength of the electromagnetic spectrum that is not
| actively being generated, is decaying. At minimum the expanding
| universe saps frequency.
|
| More directly,radiation (light,photons) is absorbed and re-
| emmited by matter but the re-emitted energy is always at a
| lower frequency.
|
| This absorbed & re-emitted longer wavelength radiation is what
| can become trapped.
| squokko wrote:
| I can't imagine that contrails are a significant percentage of
| cloud cover.
| infradig wrote:
| Less than 1% globally, so you're right.
| smakt wrote:
| This is bullshit. How can anyone pretend the radiation
| reflecting from it is significant? How wide are these things?
| 20 meters?
| stevage wrote:
| There are a lot of them.
| stevage wrote:
| This is the terrible argument that leads so many countries to
| do nothing to reduce their emissions. Each country is a small
| portion of the total so they all do nothing.
| anigbrowl wrote:
| It'd be worth it just to shut the chemtrail nuts up.
| blipvert wrote:
| You don't understand conspiracy loon logic. By the very act of
| hiding the chemtrails you are demonstrating that you are doing
| something nefarious.
| ryandrake wrote:
| Plus, the invisibility of a thing does not stop the
| conspiracy loons from building conspiracies around it. 5G RF
| is invisible, yet still being used by the government to
| control our brains. For chemtrails, the conspiracy is just
| going to turn into: "They're spraying _invisible_ chemicals
| all over us to turn us into communists. " There's no end to
| it.
| cousinbryce wrote:
| All I'm saying is I haven't seen any contrails since the
| government shutdown
| tbrownaw wrote:
| > _5G RF is invisible, yet still being used by the
| government to control our brains._
|
| Well it's one of the main last-mile mediums people use to
| doomscroll their propaganda feeds, so... yes?
| PunchyHamster wrote:
| They will find next conspiracy theory to cling on, if any thing
| keeping them in currently relatively harmless spot is an
| advantage
| lupusreal wrote:
| _" The government conspired to reduce our cloud cover! Aaaaaa"_
| anon291 wrote:
| I hate to break it to you, but the individual chem-trails that
| you can only see with my patented tin foil glasses are more
| dangerous than the visible ones. If you knew about the people
| trying to control you, you would know all about this.
| api wrote:
| They'll say it's proof they invented invisible mind control
| agents.
|
| You can't reason (or evidence) someone out of a position that
| isn't based on reason.
| like_any_other wrote:
| To be fair, most gasses and even aerosols are effectively
| invisible to the naked eye. Not to mention viruses, prions,
| bacteria, spores.. some of which affect behavior (rabies, mad
| cow disease, and the famed cordyceps for ants).
| lukan wrote:
| Yes, but I experienced those nuances are lost on people,
| who think smoke is just water vapor otherwise.
|
| And if planes are making visible clouds one day and the
| other not, it is obviously because they are not spraying
| all the time, etc.
|
| So no more clouds would not make people smarter, but it
| might actually reduce this particular conspiracy spread.
| the__alchemist wrote:
| This is something the military, e.g. fighter jets worry about.
| The altitudes (in a given airspace) that form contrails are
| briefed as part of "tactical weather". You try to avoid them if
| able, because no matter how stealthy you are, you are lit up for
| all to see if you fly at those altitudes.
| aerostable_slug wrote:
| Fun fact: the B-2 bomber has a LIDAR-based contrail detection
| sensor, called the Pilot Alert System.
|
| https://tridsys.com/our-divisions/optical-precision-sensors/
| Den_VR wrote:
| There's always been something disturbing about public
| internet advertisements of military equipment. I suppose it's
| dual use, but it seems like baiting a malicious actor to play
| with it in detail.
| Agree2468 wrote:
| If you're ever in DC, you should check out the ads in the
| metro stops near the Pentagon. Seeing those kinds of ads in
| real life is even more shocking.
| Retric wrote:
| Walked into a weapons show a few decades ago that had a
| full scale Abrams tank + demo camera providing good 360
| degree visibility.
|
| It was odd because I was like yea this is obviously a
| good idea, but also I'm not the person you need to
| convince here so WTF.
| kiba wrote:
| It's designed to convince their customers which are other
| countries.
| extraduder_ire wrote:
| I saw some photos of those ads on twitter a few years
| back about a certain manufacturer's engine being the
| correct choice for a specific in-development military
| plane.
|
| It's weird seeing physical advertising be so targeted.
| Like, multiple physical ads to target less than a dozen
| people total.
| jMyles wrote:
| > If you're ever in DC, you should check out the ads in
| the metro stops near the Pentagon. Seeing those kinds of
| ads in real life is even more shocking.
|
| "Vulgar" is the word I'd use. Like a child sneaking out
| of the house to play with gasoline and matches.
| nickff wrote:
| Avoiding con-trail creation has been a factor for military
| aviation since at least WWII; bomber pilots then were briefed
| on what altitudes to fly at to avoid them as well, but not
| because they were especially stealthy.
| thaumasiotes wrote:
| There's still some space between "not especially stealthy"
| and "drawing an enormous arrow in the sky pointing directly
| to you".
| citizenpaul wrote:
| Its nice to see new tech being used to kill people for a
| change.
| aeternum wrote:
| This seems pretty useless in an age with super cheap 8k cameras
| and novice ability to do a delta-recorded image.
| Havoc wrote:
| What do you mean by delta-recorded image?
| denkmoon wrote:
| If it were all that simple would you not expect at least one
| of China, Taiwan, Iran, Israel, Ukraine, Russia to deploy
| such a technology?
| DominikPeters wrote:
| Given that the warming impacts of contrails are short-lived
| (roughly a day), I think it is a good idea to do research now on
| the weather forecasting needed to avoid producing contrails. But
| I don't really see a reason to actually start avoiding them now,
| with the associated costs in terms of fuel, CO2 emissions, and
| time. We can start avoiding them in a few decades when it might
| have become urgent to have cooling.
| evnp wrote:
| Aren't the impacts perpetual if we're creating new contrails
| every single day?
|
| Taken from another comment, this seems pretty clear:
|
| > Contrail cirrus may be air traffic's largest radiative
| forcing component, larger than all CO2 accumulated from
| aviation, and could triple from a 2006 baseline to 160-180
| mW/m2 by 2050 without intervention.
|
| [1] https://en.wikipedia.org/wiki/Contrail#Impacts_on_climate
|
| The original article describes associated costs in time and
| fuel usage in the realm of 1% increase.
| stevage wrote:
| It is already urgent.
| lukan wrote:
| It was urgent 40 years ago.
| stevage wrote:
| No. Addressing CO2 production was urgent then but the
| actual impacts of heat were not. They are now.
| SupremumLimit wrote:
| Not sure how you haven't noticed, but climate change is already
| affecting precipitation and drought patterns, it exacerbates
| heatwaves, cold snaps, and flooding, it affects harvests,
| disrupts ecosystems etc. etc. Reducing warming is an urgent
| matter.
| SyzygyRhythm wrote:
| The article mentions that some flights produce a net cooling
| effect. I wonder if it could be cost effective to divert flights
| _toward_ contrail formation when it 's predicted that they'll
| produce cooling (I also wonder what the actual circumstances are
| when they produce cooling--low surface temperatures, maybe?).
| stevage wrote:
| Perhaps also early morning flights where most of the contrail's
| lifespan will be in sun.
| exabrial wrote:
| Did I miss the part of the article stating what percentage of all
| effects this would have? Like if it moves the needle 0.000001% is
| it worth the effort? Not to play whatabouttism, but the top 8
| countries after China (US through Germany) together emit about
| the same amount of CO2 as China alone. Not saying we shouldn't
| improve where we can, as the sum of many small efforts helps the
| whole.
| Oarch wrote:
| I'm wondering if I missed this too. The percentage of the sky
| covered in contrails must be... absolutely minimal?
|
| If it was even 1% we'd surely be up in arms about how awful it
| looked.
| maltyr wrote:
| > How, then, do contrails stack up in terms of total warming?
| They contribute roughly 2% to the world's effective radiative
| forcing; tackling them would reduce that by a similar amount.
| exabrial wrote:
| Thanks, that is quite signficant
| bitwize wrote:
| But then how would the government disperse mind-control chemicals
| over the public?
| NedF wrote:
| > could be incredibly cheap
|
| Outright lie.
|
| Only contrails formed at night matter, daytime contrails reflect
| light and certainly should not be reduced, we should be
| increasing these with longer lasting chemicals for "$5", if you
| wish this can 'offset' the nighttime ones rather than this
| ridiculous proposition to re-rout traffic.
|
| It would be fair to reduce nighttime contrails over cities in
| summer, this has real value for the expense. We already mess with
| this air traffic for less important reasons.
| stevage wrote:
| The article addresses this and contradicts you, with scientific
| papers.
| sfink wrote:
| The article claims that the warming effect from bouncing heat
| back down is overall larger than the cooling effect from
| bouncing heat back up. If you disagree with this assertion,
| you'll need to say why, not just call someone a liar.
|
| The article does agree that 9% of contrails have an overall
| cooling effect, and perhaps that could be magnified by a larger
| or more persistent contrail.
| ThinkBeat wrote:
| Somehow telling airlines to fly what might be quite a bit longer,
| in order to avoid all the different contrail potenial spot, that
| will use even more fuel migth nto be a popoular sell?
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