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 21 hours ago [-]
Fun fact: the B-2 bomber has a LIDAR-based contrail detection sensor, called the Pilot Alert System.
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 20 hours ago [-]
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.
extraduder_ire 20 hours ago [-]
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.
jfengel 18 hours ago [-]
It's a little broader than that, because these are general defense contractors who have their fingers in every pie. So it's seen by contracting officers, partners, potential employees, etc.
It's a bit like a Coke ad -- you do not need to be informed about Coke, but it creates an atmosphere of nebulous positive feelings. Still, kinda weird.
Cthulhu_ 5 hours ago [-]
It makes sense though, given that those dozen people have decisive power to bring billions of dollars in revenue and decades of work to the companies advertising.
Like, the Dutch airplane manufacturer Fokker went bankrupt and stopped manufacturing planes in 1996, but the brand and company are still very much alive, manufacturing parts and providing maintenance services to all their planes still in operation worldwide.
imglorp 7 hours ago [-]
If you think advertising to a dozen people is wild, wait till you hear about bribery of six! It's more efficient!
sjf 18 hours ago [-]
[The I-80 east has entered the chat]
Agentlien 12 hours ago [-]
I'm someone living far off in remote Sweden, could you explain with some examples?
datadrivenangel 18 hours ago [-]
The tech billboards in SF are also wild.
Retric 20 hours ago [-]
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.
Cthulhu_ 5 hours ago [-]
You're not but there may be people that are. Besides, tanks are cool and I'd go to shows like that for entertainment purposes. I went to the Dutch military museum the other day, it has a Leopard tank outside (and of course a collection of tanks and the like indoors, including a German V2 rocket suspended from the ceiling).
varenc 19 hours ago [-]
How'd you find a weapons show? Which one? are these semi-open to the public? Sounds fascinating
Retric 18 hours ago [-]
I was walking around Arlington VA area and saw some signs of fighter jets and such that looked interesting, no idea of the show beyond that really.
I did have a pentagon badge at the time which let me in, not sure if it was necessary though.
kiba 20 hours ago [-]
It's designed to convince their customers which are other countries.
bigfatkitten 6 hours ago [-]
The billboards at Canberra airport almost exclusively advertise defence contractors.
Lockheed Martin, BAE Systems, Northrop Grumman and Qinetiq know how to reach their audience.
jMyles 20 hours ago [-]
> 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.
Our capital (if such a thing even remains relevant) will feel much more dignified when there's no incentive to hock machines of death in the public transit.
philipallstar 6 hours ago [-]
This is the sort of response I'd hope an AskJeeves AI would generate.
ecshafer 6 hours ago [-]
If you desire peace, prepare for war.
quesera 5 hours ago [-]
If your preparations for war are influenced by advertising in the DC Metro, you are not a serious professional who the public can trust to desire peace.
protocolture 17 hours ago [-]
If anything there should be more public info.
Seeing people having to FOI request details of the chemicals they were exposed to in their service, is much more disturbing.
tintor 15 hours ago [-]
B-2 is not dual use. There is no civilian use for it.
aklemm 6 hours ago [-]
We can bomb immigrants and protestors. Let your imagination soar in these innovative times!
LargoLasskhyfv 11 hours ago [-]
There could be. As in "Fight fire with fire!" For stopping out of control forest fires, by bombing large and wide trenches, to stop them there.
Angostura 7 hours ago [-]
Search and rescue? /s
wil421 19 hours ago [-]
A malicious actor is probably not going to meet them at their place of business and do FBI background checks, in person DOD interviews, even polygraphs, to be able to really talk to them.
19 hours ago [-]
nickff 21 hours ago [-]
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 21 hours ago [-]
There's still some space between "not especially stealthy" and "drawing an enormous arrow in the sky pointing directly to you".
aeternum 20 hours ago [-]
This seems pretty useless in an age with super cheap 8k cameras and novice ability to do a delta-recorded image.
nine_k 19 hours ago [-]
Numbers don't add up.
If you take a 8K camera with a standard 50 mm lens, its angular resolution is about 20" / pixel.
A 50 mm lens has a FOV of about 40°. It covers a cone of about 0.38 strad. A full hemisphere has 2·pi = 6.28 strad, so we need at least 16.5 such cones to cover the whole area; actually we need likely 20-25 because of imperfect geometry and some safety margins at intersections. We can, of course, mount fewer and scan.
If we take a plane like A320 (larger than a typical fighter jet), and remove it 25 km from us, its angular size would be about about 5', or 300". Our A320 would be 15 pixels wide, assuming very good optics, and very clear skies. This is not much to determine what craft is approaching us. At the cruise speed of 800 km/h, or 220 m/s, the plane will reach us in 122 s, or less than 2 minutes. Not a lot of warning. A fighter jet making 500 m/s would be there in 50 s.
This is, of course, without any clouds. Even very light clouds or haze would conceal the aircraft at 25 km. To say nothing of the night time.
We could of course take in IR camera, but I don't remember 8K IR cameras being cheap, or even available. A stealth aircraft like B-2 does a lot to make its thermal signature very faint, including the exhaust.
MindSpunk 8 hours ago [-]
IR sensor based tracking has existed for decades [1]. But aircraft equipped with them still equipped radar systems because of their significantly longer range tracking capability. Optical has all the same downsides as IR tracking, on top of not working at night. It's like people forget that radar relies on the scanning aircraft to actively illuminate their targets with the radar emitter, where as optical systems rely on the sun to do that. Targets are at least partially self illuminating for IR trackers thanks to the hot jet engines.
You don't need to identify the A320 from 15 pixels. Once you see a 15 pixel signature that changes between subsequent frames you point the one extra camera on a movable mount with a 600mm lens on it at it. Now you get a few hundred pixels.
aeternum 17 hours ago [-]
Most camera sensors already detect in the IR range, you just need to remove the filter. I've done it, works great and pretty fun to convert some old webcams, robot vacuums lidar scanners look especially cool.
Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easier with satellites. Stealth effectively no longer exists for most nation-state level tech. The B-2 is a very cool plane but is unfortunately obsolete. Still great for when you want to put on more of a show than an attack.
Tor3 13 hours ago [-]
"Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easier with satellites."
This is incorrect. A typical satellite will orbit once every 100 minutes or so (military spy satellites more often because they fly lower, but that only makes the next part even worse). To have any kind of resolution the swath it can scan is very narrow. It'll pass from horizon to horizon in some 10-14 minutes or so, if if passes reasonably overhead (which it'll do once, the next orbit it'll be far from overhead or not seen at all, depending on your latitude).
For a satellite to spot an airplane you need to be in luck. A coincidence. It's not something you can use for spotting airplanes. The harder you look (the more you increase resolution) the more narrow the swath gets. You can have more satellites. There's still no chance of actively detecting airplanes on a regular basis. And this doesn't even take into consideration that the data must be processed after having been dumped from the satellite. The satellite is by then elsewhere.
You could use a geostationary satellite, to monitor a good third of the planet at once. But then you're nearly 36000km above equator and you can't see any details. So, not that either.
Satellites are great for scanning the surface of the planet. And for that we're now at a stage where it's hard to hide anything, for very long at least. But moving airplanes is something entirely different.
(My job is about processing data from satellites).
overfeed 2 hours ago [-]
> A typical satellite will orbit once every 100 minutes or so (military spy satellites more often because they fly lower,
Constellations (like Star Shield or the Chinese equivalent) solve this problem; there is always a dozens of satellites overhead, and they don't need a lot of resolving power to detect contrails, I vet even cubesats with repurposed phone-camera sensors would suffice.
myself248 8 hours ago [-]
> Most camera sensors already detect in the IR range, you just need to remove the filter.
Yes, but no. "Infrared" is a very wide range, and you're talking about different things here.
"Just off the red end of the visible spectrum", aka near-IR is typically considered 700-1400nm, which is what your normal visible-spectrum camera becomes sensitive to when you pop off the filter. That's fun, and you'll find lots of cool things there. Remote controls use near-IR typically in 850nm, flowers often reflect vividly in this range too. Notably, near-IR passes through most materials that're clear in the visible spectrum, which is how bugs are able to have eyes that see it to locate those flowers. Also, plastics and glasses, so NIR-capable optics are cheap. (NIR windows are often dyed to look dark-purple or black to the visible spectrum, because these dyes are transparent to IR.)
However, "thermal infrared" is much longer -- rocket exhaust can be seen with a mediumwave-IR sensor in the 3000-8000nm range, but warm bodies only start to show up in longwave-IR, 8000-15000nm. Sensors for those are mindbogglingly harder to make than near-IR. And these wavelengths don't pass through normal materials. Plain old glass, for instance, is totally opaque to thermal wavelengths, so if you take a thermal picture (a thermograph) of a window, you don't see the warm bodies inside, but rather the temperature of the glass itself, combined with whatever outside objects are reflected off its surface -- it acts like a mirror, not a window.
This means making lenses for thermal cameras is also difficult and expensive. The materials are awful -- Zinc Selenide is one of the most common, despite being expensive and toxic so it's difficult to machine. Pure Germanium works, but it's even more expensive. Sodium Chloride is amusingly transparent to LWIR but it tends to dislike getting rained on.
Removing the hot-mirror from a visible-light camera is a neat party trick and does legitimately see into "the infrared", but that's not the same as thermal infrared, which does still require specialized equipment.
aliher1911 11 hours ago [-]
Curious if you saw any difference in far IR vs near IR on cameras with removed filters. When I tried camera without filter or camera with IR filter (one that only lets IR through and look redish black to naked eye) attached I had nice b/w images of trees on long exposures or better pictures of tv remote leds. But if I make a picture of an iron or pan they look the same when either cold or hot.
This is very different from thermal cameras I used where you can clearly see unevennes of the pan heat, dark image on tshirt being warmer on the sun, person at night etc.
I can speculate that thermal exhaust falls into the second category.
6mian 9 hours ago [-]
In visible range, would. The technique shown in the video work not perfectly clear sky conditions? Clouds are not uniform layer that moves with exactly the same speed in each point.
Are there reliable ways to figure out which pixels on subtracted frames are cloud movement and which are the few ones that are an aircraft?
Correct me if I'm wrong, but adding extra cameras doesn't seem to solve this problem, each source reporting "almost everything moves" would make solving intersections and tracking them impossible, because each target candidate can be assigned to many changes pixels in consecutive frames. Unless some additional pattern detection is done, but again it's hard for very small objects.
nine_k 15 hours ago [-]
Does a consumer-grade 8K camera sensor detect a 20°C difference in a few pixels? Cameras have to aggressively fight against thermal noise. Visible light is much more energetic than IR; detecting a faint IR signal with a sensor which is about as hot as the object it's looking at is hard. You need to cool the sensor down; old military aircraft even carried a tank of liquid nitrogen for that.
I mean, yes, you can take a low-noise sensor, add cooling, add a telescope lens so that you'd see the shape more readily, put a bunch of these telescopes on a rotating platform to scan the sky, etc. This is doable, but the thread started with an idea that it's doable with consumer-grade ("cheap") tech. I doubt that.
While at it, even if we assume that stealth does not exist for fast and heavy aircraft, it seems to effectively exist for slow, lighter-weight drones. Ukrainian drones, built from ultralight aircraft like Aeroprakt A-20, somehow penetrate 700 miles into Russian territory to burn refineries. With a cruise speed of 70 mph (sic), it should take them 10 hours to fly this distance. Were they detected efficiently, that would be enough time to scramble an interceptor a hundred times. Apparently this does not happen.
aeternum 14 hours ago [-]
How many of those attacks were successful? Russia has fairly advanced radar that is quite capable of picking up a plane like that. I think the more likely explanation is that it was incorrectly deemed not a threat or a minor threat.
700 miles is far more than the standard range of the A-20 (210nm). Is it possible they launched it from well within Russia thereby making it much less likely to be considered a threat?
joha4270 12 hours ago [-]
Possible, just like Russel's teapot.
But there has been one very well published Ukrainian attack launched from Russian soil[1].
If Ukraine had could regularly smuggle several drone aircraft's and explosives into Russia and launch them, we would be seeing a lot of other effects. Such as attacks on weapon production sites deep into Russia[2].
But yes, a lot of those attacks are probably unsuccessful. With my qualifications as armchair general, I would be surprised if more than 10% of them was successful.
I also don't think they'll target the Yelabuga drone factory with a drone when they could use that drone on something relatively small but high value (like an aircraft) or combustible (like a refinery), and are waiting for their heavy cruise missles to come online for targets like factories. You can't do much damage to a factory with a drone. We've seen Ukraine target industrial sites with drones, but it's not common.
nine_k 11 hours ago [-]
These attacks were so successful that Russia is having fuel shortages right now, and decreased its exports of oil products by about 10%. It is estimated that about 30% of Russia's refining capacity is disabled by now. (E.g. https://www.bbc.com/news/articles/czx020k4056o)
So no, these are not isolated incidents, this is a big hole in air defense, and Russia used to produce some competent air defense systems. They are just not geared towards the drones, much like Patriot air defense systems are not either.
aeternum 27 minutes ago [-]
I agree the attacks were successful, I just don't agree they were successful because of lack of detection.
You generally can't continually launch a even $1mil missiles at $100-$10k drones and expect to win. The problem is that most air defenses were designed in an age where the enemy aircraft were quite expensive so it wasn't so critical to optimize ordinance cost. That IMO is the primary challenge for all militaries now.
mapt 6 hours ago [-]
> This is not much to determine what craft is approaching us.
Why do you have to do that exactly? Aircraft identification and aircraft detection are very different tasks. For detection, you need a tiny fractional difference in illumination (<1%) of one single pixel, that persists over time, and which shows up on two or three cameras separated for parallax.
The Youtube channel Consistently Inconsistent has been doing a series on optical detection, after an offhand Elon Musk comment.
Anything detected can be subjected to closer inspection with radars, optical telescopes, and infrared telescopes.
LargoLasskhyfv 9 hours ago [-]
Still making sounds. And usually not less than an A320. May be supersonic though. So even less time to adapt/react.
Anyway. Combine with microphone arrays, and your coverage is better.
8 hours ago [-]
denkmoon 19 hours ago [-]
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? To me this recently popular idea that you can just point a load of cameras at the sky to beat stealth is disproved by the lack of such installations. These are fairly motivated actors.
cyberax 19 hours ago [-]
> To me this recently popular idea that you can just point a load of cameras at the sky to beat stealth is disproved by the lack of such installations.
Russia has a 10x advantage over Ukraine in aviation, yet it only uses it to lob guided bombs from safely beyond the Russian border. The anti-air defense far outmatches the stealth of Russian airplanes.
They are not the stealthiest, sure. But there are reasons to think that NATO planes are not going to fare much better.
18 hours ago [-]
Havoc 19 hours ago [-]
What do you mean by delta-recorded image?
bob1029 19 hours ago [-]
The fixed resolution of an image sensor can be augmented by capturing multiple frames over time.
Super resolution is a thing but I think they mean to just take the differences and track based on the motions in that data directly. Any deltas which appear to move in a certain way are likely to be aircraft, especially if the same deltas show up on a 2nd camera, even if they aren't clear enough to directly identify. Basically the motion vector estimation step of video encode but tuned really tight and ignoring motions that don't look like aircraft motions.
I'm not sure this is really all that perfect/foolproof though, especially with 8k visible light cameras. For one, clouds can be quite the problem (even at non-visible wavelengths). Atmospheric turbulence can also be annoying and the air can be plain hazy depending on the day - both limit detection accuracy at a given range. When night comes the detection ability is greatly hampered even with additional wavelengths (and IR has lower resolution anyways).
It worked well enough in a weekend project many years back to use computer vision (the craze at the time) and compare to an ADS-B make by using a 4k 1 FPS image feed in a weekend project to mess with computer vision a decade back. I definitely see it as a valid addition to a detection system... but I would stop short of writing a "Military Dumbfounded at This One Simple Trick" article about it.
Its nice to see new tech being used to kill people for a change.
anigbrowl 22 hours ago [-]
It'd be worth it just to shut the chemtrail nuts up.
blipvert 22 hours ago [-]
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 22 hours ago [-]
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.
tbrownaw 20 hours ago [-]
> 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?
solid_fuel 19 hours ago [-]
It's funny how often the conspiracy types are both right and wrong. We have precision targeted ~~propaganda~~ content streaming straight to the tracking device everyone willingly carries, but they land on 5G being some sci-fi form of mind control.
It's some form of motivated reasoning. The same people who will tell you a secret cabal of billionaires controls the government will roll their eyes if you bring up the heritage foundation.
deeg 16 hours ago [-]
I can't upvote this enough.
I would find CT believers fascinating if it also wasn't sad. I have one in the family and she lives below the poverty line and has been missing most of her teeth since her late forties (fluoride works, people).
meindnoch 10 hours ago [-]
It's like those bell curve memes.
add-sub-mul-div 18 hours ago [-]
They can't abide pretend child endangerment happening in pizza basements, but point out the Catholic church or Trump perving on Miss Teen USA contestants in their dressing room and they don't seem to care.
cindyllm 17 hours ago [-]
[dead]
voidUpdate 11 hours ago [-]
How do you know they arent already spraying invisible communist chemicals all the time? * Adjusts tinfoil hat *
SapporoChris 8 hours ago [-]
I enjoy the conspiracy theories about conspiracy theories.
cousinbryce 21 hours ago [-]
All I’m saying is I haven’t seen any contrails since the government shutdown
api 21 hours ago [-]
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 21 hours ago [-]
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 20 hours ago [-]
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.
Are the fumes less bad, when they don't leak into the cabin by bleed air, just blown away backwards?
The solution to pollution is dilution (in the atmosphere)? With the current amount of global air traffic, no matter if civilian, or military?
tecleandor 9 hours ago [-]
But that's not chem-trails!
PunchyHamster 21 hours ago [-]
They will find next conspiracy theory to cling on, if any thing keeping them in currently relatively harmless spot is an advantage
nntwozz 19 hours ago [-]
I clicked comments to search for chemtrails, I was not disappointed.
anon291 21 hours ago [-]
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.
lupusreal 21 hours ago [-]
"The government conspired to reduce our cloud cover! Aaaaaa"
_carbyau_ 19 hours ago [-]
"Without those clouds the alien mind control rays from space will get you more often. You think it's deja vu don't you? Better get your tinfoil hat prepped."
apercu 20 hours ago [-]
[flagged]
morkalork 20 hours ago [-]
Did you just update your profile or did opportunity strike again?
apercu 5 hours ago [-]
I would answer but then I am commenting on HN again. ;)
bregma 8 hours ago [-]
Real chemtrails are already invisible. When you see a contrail it's because the jet engines have been poorly maintained to cut costs and increase quarterly returns to the shareholders.
5 hours ago [-]
rkomorn 8 hours ago [-]
How are contrails related to engine maintenance?
pavel_lishin 23 hours ago [-]
I had no idea contrails actually caused that much warming, compared to the exhaust.
Nzen 23 hours ago [-]
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.
> 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.
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 20 hours ago [-]
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.
The original article describes associated costs in time and fuel usage in the realm of 1% increase.
SupremumLimit 20 hours ago [-]
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.
wasabi991011 19 hours ago [-]
Given the feedback loops associated with climate change, I'd expect early interventions to have a larger impact on the climate than later ones.
stevage 20 hours ago [-]
It is already urgent.
lukan 20 hours ago [-]
It was urgent 40 years ago.
stevage 20 hours ago [-]
No. Addressing CO2 production was urgent then but the actual impacts of heat were not. They are now.
lukan 19 hours ago [-]
But the warming started already back then. Contrails contributed. So less contrails, less warming in the last 40 years.
14 15 hours ago [-]
There was a really good section of the article that went into great detail of the math and how it would easily outweigh the CO2. How it would only require something like diverting 2% of all flights as it is only that percentage of flights that make the majority of the contrails and that the diversion of the average flight would be something small like an extra 2 minutes flight time for shorter flights and like 6 minutes on a longer flight which the article states is not much increase in fuel consumption as well as not such a time increase to dissatisfy customers. So if the article is accurate in their math then the associated costs in all three fuel, CO2, and time are not an issue.
SyzygyRhythm 21 hours ago [-]
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 20 hours ago [-]
Perhaps also early morning flights where most of the contrail's lifespan will be in sun.
ZeroGravitas 9 hours ago [-]
One of the touted benefits of e-fuel is the purity that after combustion reduces the exhaust soot.
I wonder if factoring in the contrail reduction of this tilts them towards financial breakeven.
edit: Googled it and an Airbus test last year suggested a 25% decrease in contrail formation:
N2O (laughing gas) is not combustible, but autodecomposes into a mixture composed of 1 part oxygen gas and 2 parts nitrogen gas, which happens to be the approximate composition of the atmosphere.
In theory we could design and use N2O engines and airplanes etc, and their exhaust could be a gas that is nearly equivalent to atmospheric composition.
One important issue is making sure all the N2O has decomposed because it is a very potent GHG.
Would N2 and O2 create contrails? in what sense is it distinct from atmosphere?
klodolph 19 hours ago [-]
Someone can break out their chemistry references, but I think N₂O is probably not workable as a fuel (or at best, not very good). It forms naturally in internal combustion engines, from air, at the temperature and pressures found in engines, given O₂ and N₂. If something has the habit of forming in an engine, I don’t think you could use it as fuel, but my thermodynamics is a bit too rusty to do any kind of ELI5 and I could just be wrong here. At the very least, it would be difficult to use or inefficient.
It decomposes into N₂ and O₂ at normal atmospheric temperatures and pressures, outside an engine.
topaz0 15 hours ago [-]
You're probably thinking of NO2, which is indeed a pollutant that results from overly hot combustion in air. N2O is in fact used in engines, but it is not the fuel -- rather it is a supplementary oxidizer, which allows you to burn more fuel and therefore produce more power than you could if you only had the oxygen from air. At any rate, that means using N2O won't be a solution to the aircraft fuel problem -- you'd still need a combustible fuel for it to oxidize.
DoctorOetker 5 hours ago [-]
You are correct that N2O is the "nitro" afterburner used in different systems.
But the reaction 2 N2O => 2 N2 + O2 is very exothermic, in fact it is explosive (but not in the burning sense, since its autodecomposition). However adding a small amount of ethanol makes N2O stable so that sudden shocks or compressions don't result in initiating autodecomposition or explosion.
To power an engine one doesn't necessarily need to burn, or a redox reaction to happen, the reaction just needs to be exothermic and N2O is very exothermic.
topaz0 3 hours ago [-]
I stand corrected.
cyberax 19 hours ago [-]
N2O formation enthalpy is just 82kJ/mol. For comparison, water is 240kJ/mol.
It doesn't sound so bad, but when translated into grams, it's 1.86kJ/g for N2O and 13.3kJ/g for water.
In other words, when burning a gram of hydrogen, you get about 120kJ of energy. When decomposing a gram of N2O, you barely get 2kJ.
saagarjha 10 hours ago [-]
You’re off by a factor of 10 somewhere
cyberax 1 hours ago [-]
Nope? A gram of water is mostly oxygen. Hydrogen is just 2/18 of the water mass, so that's where the factor of 9 comes from.
LargoLasskhyfv 13 hours ago [-]
Fume events would be more funny, then!
6 hours ago [-]
rafa___ 5 hours ago [-]
I would be very skeptical of any "super cheap solutions" to anything in aviation... almost nothing in commercial aviation is "cheap"
padjo 6 hours ago [-]
As someone who lives near a flight path and has clear skies constantly ruined by contrails this would be fantastic from a purely aesthetic perspective.
crazygringo 17 hours ago [-]
I'm so confused. This article is explaining that eliminating contrails would have a significant effect on warming.
But contrails are just the tiniest, tiniest fraction of the sky somewhere and only last over a given area for a few minutes generally. Like, sure, if you live next to a busy airport maybe you see them more often, but that's balanced out by the 99.9% of sky not next to a busy airport. Plus the many days that they just don't show up at all, because they depend on certain weather conditions.
I mean, this just doesn't pass the smell test.
But Wikipedia has an entire section [1] full of citations. But then... it sounds like maybe a lot of them aren't credible or suggest that it's not a problem? E.g.:
> However, follow-up studies found that a natural change in cloud cover can more than explain these findings. The authors of a 2008 study wrote, "The variations in high cloud cover, including contrails and contrail-induced cirrus clouds, contribute weakly to the changes in the diurnal temperature range, which is governed primarily by lower altitude clouds, winds, and humidity."
> Then, the global response to the 2020 coronavirus pandemic led to a reduction in global air traffic of nearly 70% relative to 2019. Thus, it provided an extended opportunity to study the impact of contrails on regional and global temperature. Multiple studies found "no significant response of diurnal surface air temperature range" as the result of contrail changes, and either "no net significant global ERF" (effective radiative forcing) or a very small warming effect.
So it sounds like this theoretical contrail warming problem possibly doesn't exist? I find it strange the article doesn't even acknowledge any discussion over whether it's actually a problem in the first place.
> But contrails are just the tiniest
> tiniest fraction of the sky somewhere
Initially yes, but as a contrail diffuses it acts like a seed for wider cirrus cloud formation.
During COVID lockdown, researchers at Universität Leipzig found that the reduction of air travel correspondingly reduced cirrus formation by 9% in the area studied.
Theodores 11 hours ago [-]
Check out satellite images and look at the clouds closely. Or, better still, try and predict rain just from the images. Chances are that you will be predicting a lot more rain or 'overcast days' than what you will get.
I am based in the UK and there are clear flight paths, for example, the big airport is west of London (Heathrow) and a lot of planes fly west to the 'New World'. A typical route will be over the Bristol Channel, which is over water rather than land. If you look at the satellite imagery in the different wavelengths then you will see the whole Bristol Channel 'clouded' with what can only be contrails.
If you are old enough then you might be able to remember 9/11 and the skies in the aftermath, when no planes were flying for quite a few days. The pandemic gave us a glimpse of this too, however, we were shutting down a lot else then.
To summarise, we are pissing in the pool big time with this aviation lark. I appreciate that you can't see it, but I don't think anyone that is heavily car dependent actually will. It is a 'wood for the trees' thing, and, if you are always around cars, trucks and planes, you are in the pool of piss and just not seeing it or smelling it.
You can see this filth if you get out of town, climb a hill and look back. If it is a clear day with a big sky and no wind, then you should be able to see the filthy air above the town, and that isn't from people riding bicycles.
What we have done with cars is to make them more efficient. Nobody is rolling coal any more, well, maybe in South Carolina, but everything was 'rolling coal' with added lead until relatively recent times. There might not be clumps of soot the size of snowflakes in the air, what happens now is that the car dependent person has a vehicle that burns the same amount of fuel as before, but the particle sizes that come out the back are extremely small, so small that you can't see them. But you can see them if you happen to be using a satellite to do so, or if you do get ten miles out of town on a clear day, and look at it properly.
I live in Scotland where we have had an interesting history with air quality. We have a network of paths that are made from former railway lines and canals that take you a long way from cars. There are stretches where you are riding through nothing but flowers for mile after mile. You can also unlock extra adventure levels to find networks of roads that don't exist on Google Maps that are closed to cars but definitely open to bicycles. However, eventually, some big road will need to be crossed or there will be a road running parallel to the trail. Then the magic ends.
What amazes me is how you can get used to the wonderful smells of the truly clean air to then be utterly appalled at how toxic the air is anywhere within a mile of a car. But, inside a car,the air always smells good, right? It is not as if you get tired from carbon monoxide poisoning on longer journeys, is it?
So, does any of this matter? Not if you are young with no health problems. Just suck in the air wherever there is an abundance of vehicles. You will never know what good air is or why it matters. Besides, we all need cars and trucks to get food on our tables, so there is no escaping and it would be hypocritical to do so.
Or you can opt out, to never fly and never drive. I chose this as a challenge and, so far, no regrets. I haven't been on a plane for three decades yet I seem to know more about the world than most frequent fliers. As for not getting into a car, there are occasions such as funerals where I will get a lift, and yes, I do get the occasional item delivered to my door, but everything else? Bicycle, or electric train, powered by wind farms. It seems to me that you can only really assess the problem if you aren't part of it.
Regarding contrails, they have been a conspiracy theorist talking point for as long as the internet has been around. What is pernicious about conspiracy stories is that there is always a small grain of truth in there. All of these hydrocarbons we burn - all of them - are toxic to life and cancer causing. Conspiracy theorists have egged the pudding on this, but who wins from this? Well, it means that anyone with a preference for genuinely clean air, buzzing with bees and wonderful smells from plants, can be branded a crazy person because they must be, right?
alberth 17 hours ago [-]
I was hoping this was going to be about eliminating the heat trail of a plane.
Then learned it’s just about rerouting a flight to climate zones that will less likely form a vapor trail.
Tor3 13 hours ago [-]
But there's no physics which can remove heat from a thermal engine, other than shifting the heat to the outside.
(Science fiction books would use "heat sinks" in their war space ships to try to hide the heat for a short while, but would eventually have to dump the heat somewhere. As heat sinks are basically just a huge mass.. not an option for airplanes.)
ThinkBeat 20 hours ago [-]
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?
Tor3 12 hours ago [-]
Due to the current war airplanes from Northern Europe to Asia are already re-routed, increasing travel time from Helsinki to Japan, for example, from previously some 9.5 hours to up to 13.5 hours.
How much will it cost in fuel (additional miles) and time (flyers’ lives) to reroute?
steanne 23 hours ago [-]
> 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 22 hours ago [-]
Airlines will certainly notice a 1% fuel cost increase however. But, they'll just add it to ticket prices.
andrewflnr 22 hours ago [-]
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 21 hours ago [-]
1% less fuel will not be 1% less ticket cost, but something much less.
mulmen 22 hours ago [-]
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.
PunchyHamster 21 hours ago [-]
the question is whether the contrail produces the amount of warming equivalent to extra fuel used, of which I'm doubtful
jvanderbot 21 hours ago [-]
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.
23 hours ago [-]
stevage 20 hours ago [-]
The article addresses this in detail.
anon98356 7 hours ago [-]
It covers the impact of fuel quite thoroughly but it brushes over the time element which I think is actually a bigger factor in why they don't really do it. Passing on the fuel cost to the customer they could probably get away with but given how tightly packed the flight schedules are (particularly short haul) the cumulative extra time across even a day could be enough that they have to drop a flight from the schedule.
When you consider that RyanAir don't have seat back pockets specifically because of the extra cleaning time to clear them between flights, you can see why the extra 2 minutes flight time might matter.
dustfinger 19 hours ago [-]
There are a lot of comments here mocking “chemtrail” believers, but I think the confusion is understandable. There seems to be a mix-up between three terms: contrails, chemtrails, and cloud seeding.
Contrails are just condensation trails caused by jet exhaust and air pressure differences at high altitude.
Cloud seeding, on the other hand, is a real weather-modification technique that uses aircraft to disperse substances like silver iodide to encourage rainfall [1]
I completely empathize with people confused by this. They aren't all just a bunch of conspiracy nuts, many just don’t know how to identify what they’re seeing or how these technologies actually work. I don’t mock them, I try to educate.
The chemtrails conspiracy nuts aren't confused about cloud seeding. They believe contrails are visible evidence that airplanes are used to disperse mind control drugs over the populations below.
dustfinger 15 hours ago [-]
There are many people that believe the contrails, that they refer to as chemtrails, are about weather control. Those are the people that I think are confused. Just search "chemtrails weather control" or "manipulation". I have also spoken to many people that hold this belief.
If the incoming radiation can pass through, why can't it pass through on the way out?
burkaman 22 hours ago [-]
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...
continuational 22 hours ago [-]
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.
cvoss 22 hours ago [-]
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 21 hours ago [-]
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.
tejtm 21 hours ago [-]
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.
justonceokay 22 hours ago [-]
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.
vamin 22 hours ago [-]
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.
dylan604 23 hours ago [-]
"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.
DemocracyFTW2 22 hours ago [-]
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.
> 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 21 hours ago [-]
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 21 hours ago [-]
> 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.
> 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.
dylan604 19 hours ago [-]
For those curious about the image, but not curious enough for whatever nope not signing up modal:
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]
Well some of us are doing things to eliminate contrails ... (Shameless self promotion of my employer)
dylan604 22 hours ago [-]
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.
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 22 hours ago [-]
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 22 hours ago [-]
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 22 hours ago [-]
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 22 hours ago [-]
> 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 22 hours ago [-]
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 21 hours ago [-]
Fair enough, it was pedantic. But the distinction is exactly where conspiracists come unstuck.
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
hshdhdhehd 16 hours ago [-]
So hard to get done though. Needs global cooperation. The overlap with chemtrails and climate change means Trump might hate it on vibes and ban this correction for US airlines.
Airlines are on wafer thin margins and for the longer turnaround times affecting schedules wont love it. The fact that it is a small % is worse: if you get hit you become less competitive!
Pilots workload is increased too.
Its a great technical idea but not sure how you'd get it off the ground.
In an alternative timeline with a carbon price it may work. You get x$ carbon credits for a detour. Let the planes decide if they want it.
exabrial 21 hours ago [-]
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.
maltyr 21 hours ago [-]
> 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 21 hours ago [-]
Thanks, that is quite signficant
21 hours ago [-]
Oarch 21 hours ago [-]
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.
19 hours ago [-]
squokko 22 hours ago [-]
I can't imagine that contrails are a significant percentage of cloud cover.
22 hours ago [-]
infradig 22 hours ago [-]
Less than 1% globally, so you're right.
stevage 20 hours ago [-]
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.
smakt 21 hours ago [-]
This is bullshit. How can anyone pretend the radiation reflecting from it is significant? How wide are these things? 20 meters?
ceigey 15 hours ago [-]
That’s narrower than a Boeing 737’s wingspan, and when you look at planes leaving a trail behind them, you can often see the trail fan out much wider than the plane.
Not sure how wide that would be, but the length has to be factored in too, which begs the question, how wide and long is a piece of string/cloud?
On the ground looking up the sense of scale falls apart a bit.
stevage 20 hours ago [-]
There are a lot of them.
exasperaited 19 hours ago [-]
The claims they are making seem slightly at odds with the (I thought well-established) claims that jet emissions cause measurable global “dimming”: that is, that the pollutants reflect enough sunlight that it is accidentally retarding global warming, supporting the concern that necessarily cleaning up our air will briefly accelerate global warming itself. Are they? Or is it also a double whammy?
This was seen to be evident in global pan evaporation measurements after the essentially global flight travel bans in the few days after 9/11; I have often wondered whether the equivalent restrictions in the early days of the pandemic show it as clearly because the impacts on pollution were very striking.
huflungdung 20 hours ago [-]
[dead]
huvarda 23 hours ago [-]
[flagged]
phoehne 22 hours ago [-]
Now they're hiding the chemtrails. It's even worse!
pfannkuchen 23 hours ago [-]
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).
bitwize 20 hours ago [-]
But then how would the government disperse mind-control chemicals over the public?
cosmin800 9 hours ago [-]
Ah, yes, the solution is to pay someone to do something . An extra 3.50 euro pet flight/passenger to avoid extra contrails, genius money making machine.
NedF 20 hours ago [-]
> 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.
sfink 20 hours ago [-]
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.
lmm 16 hours ago [-]
> 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
I'm not sure they do. It's an extremely counterintuitive claim that would need to be justified, and while the author does cite (their own) paper, it sounds like the model they came up with is highly parameterised and not particularly physically validated. If it's really the case that contrails reflect more heat down than up (unlike what the scientific consensus says is true for regular clouds), then there should be an explanation for what contrail-specific factor causes this, not just "here's a pile of math equations that say it doesn't, don't ask where we got the parameters to fill them out from".
sfink 15 hours ago [-]
I'm not going to argue the point, I'm no climate scientist. But Wikipedia https://en.wikipedia.org/wiki/Contrail disagrees with you as well, so you'd need to argue with their sources too.
"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."
Shiny bright light goes through or gets scattered. Dull red blackbody radiation gets absorbed. Doesn't sound too counterintuitive to me, but again I'm no expert.
stevage 20 hours ago [-]
The article addresses this and contradicts you, with scientific papers.
Rendered at 18:23:28 GMT+0000 (Coordinated Universal Time) with Vercel.
https://tridsys.com/our-divisions/optical-precision-sensors/
It's weird seeing physical advertising be so targeted. Like, multiple physical ads to target less than a dozen people total.
It's a bit like a Coke ad -- you do not need to be informed about Coke, but it creates an atmosphere of nebulous positive feelings. Still, kinda weird.
Like, the Dutch airplane manufacturer Fokker went bankrupt and stopped manufacturing planes in 1996, but the brand and company are still very much alive, manufacturing parts and providing maintenance services to all their planes still in operation worldwide.
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.
I did have a pentagon badge at the time which let me in, not sure if it was necessary though.
Lockheed Martin, BAE Systems, Northrop Grumman and Qinetiq know how to reach their audience.
"Vulgar" is the word I'd use. Like a child sneaking out of the house to play with gasoline and matches.
Our capital (if such a thing even remains relevant) will feel much more dignified when there's no incentive to hock machines of death in the public transit.
Seeing people having to FOI request details of the chemicals they were exposed to in their service, is much more disturbing.
If you take a 8K camera with a standard 50 mm lens, its angular resolution is about 20" / pixel.
A 50 mm lens has a FOV of about 40°. It covers a cone of about 0.38 strad. A full hemisphere has 2·pi = 6.28 strad, so we need at least 16.5 such cones to cover the whole area; actually we need likely 20-25 because of imperfect geometry and some safety margins at intersections. We can, of course, mount fewer and scan.
If we take a plane like A320 (larger than a typical fighter jet), and remove it 25 km from us, its angular size would be about about 5', or 300". Our A320 would be 15 pixels wide, assuming very good optics, and very clear skies. This is not much to determine what craft is approaching us. At the cruise speed of 800 km/h, or 220 m/s, the plane will reach us in 122 s, or less than 2 minutes. Not a lot of warning. A fighter jet making 500 m/s would be there in 50 s.
This is, of course, without any clouds. Even very light clouds or haze would conceal the aircraft at 25 km. To say nothing of the night time.
We could of course take in IR camera, but I don't remember 8K IR cameras being cheap, or even available. A stealth aircraft like B-2 does a lot to make its thermal signature very faint, including the exhaust.
[1] https://en.wikipedia.org/wiki/Infrared_search_and_track
Blurry video is fine when using techniques like this: https://www.youtube.com/watch?v=m-b51C82-UE
Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easier with satellites. Stealth effectively no longer exists for most nation-state level tech. The B-2 is a very cool plane but is unfortunately obsolete. Still great for when you want to put on more of a show than an attack.
This is incorrect. A typical satellite will orbit once every 100 minutes or so (military spy satellites more often because they fly lower, but that only makes the next part even worse). To have any kind of resolution the swath it can scan is very narrow. It'll pass from horizon to horizon in some 10-14 minutes or so, if if passes reasonably overhead (which it'll do once, the next orbit it'll be far from overhead or not seen at all, depending on your latitude).
For a satellite to spot an airplane you need to be in luck. A coincidence. It's not something you can use for spotting airplanes. The harder you look (the more you increase resolution) the more narrow the swath gets. You can have more satellites. There's still no chance of actively detecting airplanes on a regular basis. And this doesn't even take into consideration that the data must be processed after having been dumped from the satellite. The satellite is by then elsewhere.
You could use a geostationary satellite, to monitor a good third of the planet at once. But then you're nearly 36000km above equator and you can't see any details. So, not that either.
Satellites are great for scanning the surface of the planet. And for that we're now at a stage where it's hard to hide anything, for very long at least. But moving airplanes is something entirely different.
(My job is about processing data from satellites).
Constellations (like Star Shield or the Chinese equivalent) solve this problem; there is always a dozens of satellites overhead, and they don't need a lot of resolving power to detect contrails, I vet even cubesats with repurposed phone-camera sensors would suffice.
Yes, but no. "Infrared" is a very wide range, and you're talking about different things here.
"Just off the red end of the visible spectrum", aka near-IR is typically considered 700-1400nm, which is what your normal visible-spectrum camera becomes sensitive to when you pop off the filter. That's fun, and you'll find lots of cool things there. Remote controls use near-IR typically in 850nm, flowers often reflect vividly in this range too. Notably, near-IR passes through most materials that're clear in the visible spectrum, which is how bugs are able to have eyes that see it to locate those flowers. Also, plastics and glasses, so NIR-capable optics are cheap. (NIR windows are often dyed to look dark-purple or black to the visible spectrum, because these dyes are transparent to IR.)
However, "thermal infrared" is much longer -- rocket exhaust can be seen with a mediumwave-IR sensor in the 3000-8000nm range, but warm bodies only start to show up in longwave-IR, 8000-15000nm. Sensors for those are mindbogglingly harder to make than near-IR. And these wavelengths don't pass through normal materials. Plain old glass, for instance, is totally opaque to thermal wavelengths, so if you take a thermal picture (a thermograph) of a window, you don't see the warm bodies inside, but rather the temperature of the glass itself, combined with whatever outside objects are reflected off its surface -- it acts like a mirror, not a window.
This means making lenses for thermal cameras is also difficult and expensive. The materials are awful -- Zinc Selenide is one of the most common, despite being expensive and toxic so it's difficult to machine. Pure Germanium works, but it's even more expensive. Sodium Chloride is amusingly transparent to LWIR but it tends to dislike getting rained on.
Removing the hot-mirror from a visible-light camera is a neat party trick and does legitimately see into "the infrared", but that's not the same as thermal infrared, which does still require specialized equipment.
Are there reliable ways to figure out which pixels on subtracted frames are cloud movement and which are the few ones that are an aircraft?
Correct me if I'm wrong, but adding extra cameras doesn't seem to solve this problem, each source reporting "almost everything moves" would make solving intersections and tracking them impossible, because each target candidate can be assigned to many changes pixels in consecutive frames. Unless some additional pattern detection is done, but again it's hard for very small objects.
I mean, yes, you can take a low-noise sensor, add cooling, add a telescope lens so that you'd see the shape more readily, put a bunch of these telescopes on a rotating platform to scan the sky, etc. This is doable, but the thread started with an idea that it's doable with consumer-grade ("cheap") tech. I doubt that.
While at it, even if we assume that stealth does not exist for fast and heavy aircraft, it seems to effectively exist for slow, lighter-weight drones. Ukrainian drones, built from ultralight aircraft like Aeroprakt A-20, somehow penetrate 700 miles into Russian territory to burn refineries. With a cruise speed of 70 mph (sic), it should take them 10 hours to fly this distance. Were they detected efficiently, that would be enough time to scramble an interceptor a hundred times. Apparently this does not happen.
700 miles is far more than the standard range of the A-20 (210nm). Is it possible they launched it from well within Russia thereby making it much less likely to be considered a threat?
But there has been one very well published Ukrainian attack launched from Russian soil[1].
If Ukraine had could regularly smuggle several drone aircraft's and explosives into Russia and launch them, we would be seeing a lot of other effects. Such as attacks on weapon production sites deep into Russia[2].
But yes, a lot of those attacks are probably unsuccessful. With my qualifications as armchair general, I would be surprised if more than 10% of them was successful.
[1]: https://en.wikipedia.org/wiki/Operation_Spiderweb [2]: https://en.wikipedia.org/wiki/Yelabuga_drone_factory
So no, these are not isolated incidents, this is a big hole in air defense, and Russia used to produce some competent air defense systems. They are just not geared towards the drones, much like Patriot air defense systems are not either.
You generally can't continually launch a even $1mil missiles at $100-$10k drones and expect to win. The problem is that most air defenses were designed in an age where the enemy aircraft were quite expensive so it wasn't so critical to optimize ordinance cost. That IMO is the primary challenge for all militaries now.
Why do you have to do that exactly? Aircraft identification and aircraft detection are very different tasks. For detection, you need a tiny fractional difference in illumination (<1%) of one single pixel, that persists over time, and which shows up on two or three cameras separated for parallax.
The Youtube channel Consistently Inconsistent has been doing a series on optical detection, after an offhand Elon Musk comment.
https://www.youtube.com/watch?v=m-b51C82-UE
https://www.youtube.com/watch?v=zFiubdrJqqI
https://www.youtube.com/watch?v=YZkLQsv3huo
Anything detected can be subjected to closer inspection with radars, optical telescopes, and infrared telescopes.
Anyway. Combine with microphone arrays, and your coverage is better.
Russia has a 10x advantage over Ukraine in aviation, yet it only uses it to lob guided bombs from safely beyond the Russian border. The anti-air defense far outmatches the stealth of Russian airplanes.
They are not the stealthiest, sure. But there are reasons to think that NATO planes are not going to fare much better.
https://www.ipol.im/pub/art/2023/460/
I'm not sure this is really all that perfect/foolproof though, especially with 8k visible light cameras. For one, clouds can be quite the problem (even at non-visible wavelengths). Atmospheric turbulence can also be annoying and the air can be plain hazy depending on the day - both limit detection accuracy at a given range. When night comes the detection ability is greatly hampered even with additional wavelengths (and IR has lower resolution anyways).
It worked well enough in a weekend project many years back to use computer vision (the craze at the time) and compare to an ADS-B make by using a 4k 1 FPS image feed in a weekend project to mess with computer vision a decade back. I definitely see it as a valid addition to a detection system... but I would stop short of writing a "Military Dumbfounded at This One Simple Trick" article about it.
https://en.wikipedia.org/wiki/Delta_encoding
Well it's one of the main last-mile mediums people use to doomscroll their propaganda feeds, so... yes?
It's some form of motivated reasoning. The same people who will tell you a secret cabal of billionaires controls the government will roll their eyes if you bring up the heritage foundation.
I would find CT believers fascinating if it also wasn't sad. I have one in the family and she lives below the poverty line and has been missing most of her teeth since her late forties (fluoride works, people).
You can’t reason (or evidence) someone out of a position that isn’t based on reason.
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.
Furthermore https://duckduckgo.com/q=toxicologic+assessment+of+jet+fuel
and https://en.wikipedia.org/wiki/Fume_event
Are the fumes less bad, when they don't leak into the cabin by bleed air, just blown away backwards?
The solution to pollution is dilution (in the atmosphere)? With the current amount of global air traffic, no matter if civilian, or military?
[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
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.
https://news.ycombinator.com/item?id=37060347
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.
I wonder if factoring in the contrail reduction of this tilts them towards financial breakeven.
edit: Googled it and an Airbus test last year suggested a 25% decrease in contrail formation:
https://www.airbus.com/en/newsroom/press-releases/2024-06-wo...
In theory we could design and use N2O engines and airplanes etc, and their exhaust could be a gas that is nearly equivalent to atmospheric composition.
One important issue is making sure all the N2O has decomposed because it is a very potent GHG.
Would N2 and O2 create contrails? in what sense is it distinct from atmosphere?
It decomposes into N₂ and O₂ at normal atmospheric temperatures and pressures, outside an engine.
But the reaction 2 N2O => 2 N2 + O2 is very exothermic, in fact it is explosive (but not in the burning sense, since its autodecomposition). However adding a small amount of ethanol makes N2O stable so that sudden shocks or compressions don't result in initiating autodecomposition or explosion.
To power an engine one doesn't necessarily need to burn, or a redox reaction to happen, the reaction just needs to be exothermic and N2O is very exothermic.
It doesn't sound so bad, but when translated into grams, it's 1.86kJ/g for N2O and 13.3kJ/g for water.
In other words, when burning a gram of hydrogen, you get about 120kJ of energy. When decomposing a gram of N2O, you barely get 2kJ.
But contrails are just the tiniest, tiniest fraction of the sky somewhere and only last over a given area for a few minutes generally. Like, sure, if you live next to a busy airport maybe you see them more often, but that's balanced out by the 99.9% of sky not next to a busy airport. Plus the many days that they just don't show up at all, because they depend on certain weather conditions.
I mean, this just doesn't pass the smell test.
But Wikipedia has an entire section [1] full of citations. But then... it sounds like maybe a lot of them aren't credible or suggest that it's not a problem? E.g.:
> However, follow-up studies found that a natural change in cloud cover can more than explain these findings. The authors of a 2008 study wrote, "The variations in high cloud cover, including contrails and contrail-induced cirrus clouds, contribute weakly to the changes in the diurnal temperature range, which is governed primarily by lower altitude clouds, winds, and humidity."
> Then, the global response to the 2020 coronavirus pandemic led to a reduction in global air traffic of nearly 70% relative to 2019. Thus, it provided an extended opportunity to study the impact of contrails on regional and global temperature. Multiple studies found "no significant response of diurnal surface air temperature range" as the result of contrail changes, and either "no net significant global ERF" (effective radiative forcing) or a very small warming effect.
So it sounds like this theoretical contrail warming problem possibly doesn't exist? I find it strange the article doesn't even acknowledge any discussion over whether it's actually a problem in the first place.
[1] https://en.wikipedia.org/wiki/Contrail#Impacts_on_climate
Initially yes, but as a contrail diffuses it acts like a seed for wider cirrus cloud formation.
During COVID lockdown, researchers at Universität Leipzig found that the reduction of air travel correspondingly reduced cirrus formation by 9% in the area studied.
I am based in the UK and there are clear flight paths, for example, the big airport is west of London (Heathrow) and a lot of planes fly west to the 'New World'. A typical route will be over the Bristol Channel, which is over water rather than land. If you look at the satellite imagery in the different wavelengths then you will see the whole Bristol Channel 'clouded' with what can only be contrails.
If you are old enough then you might be able to remember 9/11 and the skies in the aftermath, when no planes were flying for quite a few days. The pandemic gave us a glimpse of this too, however, we were shutting down a lot else then.
To summarise, we are pissing in the pool big time with this aviation lark. I appreciate that you can't see it, but I don't think anyone that is heavily car dependent actually will. It is a 'wood for the trees' thing, and, if you are always around cars, trucks and planes, you are in the pool of piss and just not seeing it or smelling it.
You can see this filth if you get out of town, climb a hill and look back. If it is a clear day with a big sky and no wind, then you should be able to see the filthy air above the town, and that isn't from people riding bicycles.
What we have done with cars is to make them more efficient. Nobody is rolling coal any more, well, maybe in South Carolina, but everything was 'rolling coal' with added lead until relatively recent times. There might not be clumps of soot the size of snowflakes in the air, what happens now is that the car dependent person has a vehicle that burns the same amount of fuel as before, but the particle sizes that come out the back are extremely small, so small that you can't see them. But you can see them if you happen to be using a satellite to do so, or if you do get ten miles out of town on a clear day, and look at it properly.
I live in Scotland where we have had an interesting history with air quality. We have a network of paths that are made from former railway lines and canals that take you a long way from cars. There are stretches where you are riding through nothing but flowers for mile after mile. You can also unlock extra adventure levels to find networks of roads that don't exist on Google Maps that are closed to cars but definitely open to bicycles. However, eventually, some big road will need to be crossed or there will be a road running parallel to the trail. Then the magic ends.
What amazes me is how you can get used to the wonderful smells of the truly clean air to then be utterly appalled at how toxic the air is anywhere within a mile of a car. But, inside a car,the air always smells good, right? It is not as if you get tired from carbon monoxide poisoning on longer journeys, is it?
So, does any of this matter? Not if you are young with no health problems. Just suck in the air wherever there is an abundance of vehicles. You will never know what good air is or why it matters. Besides, we all need cars and trucks to get food on our tables, so there is no escaping and it would be hypocritical to do so.
Or you can opt out, to never fly and never drive. I chose this as a challenge and, so far, no regrets. I haven't been on a plane for three decades yet I seem to know more about the world than most frequent fliers. As for not getting into a car, there are occasions such as funerals where I will get a lift, and yes, I do get the occasional item delivered to my door, but everything else? Bicycle, or electric train, powered by wind farms. It seems to me that you can only really assess the problem if you aren't part of it.
Regarding contrails, they have been a conspiracy theorist talking point for as long as the internet has been around. What is pernicious about conspiracy stories is that there is always a small grain of truth in there. All of these hydrocarbons we burn - all of them - are toxic to life and cancer causing. Conspiracy theorists have egged the pudding on this, but who wins from this? Well, it means that anyone with a preference for genuinely clean air, buzzing with bees and wonderful smells from plants, can be branded a crazy person because they must be, right?
Then learned it’s just about rerouting a flight to climate zones that will less likely form a vapor trail.
(Science fiction books would use "heat sinks" in their war space ships to try to hide the heat for a short while, but would eventually have to dump the heat somewhere. As heat sinks are basically just a huge mass.. not an option for airplanes.)
Of course it's a coordination problem. It probably needs to be a regulation before it will actually happen.
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.
When you consider that RyanAir don't have seat back pockets specifically because of the extra cleaning time to clear them between flights, you can see why the extra 2 minutes flight time might matter.
Contrails are just condensation trails caused by jet exhaust and air pressure differences at high altitude.
Cloud seeding, on the other hand, is a real weather-modification technique that uses aircraft to disperse substances like silver iodide to encourage rainfall [1]
I completely empathize with people confused by this. They aren't all just a bunch of conspiracy nuts, many just don’t know how to identify what they’re seeing or how these technologies actually work. I don’t mock them, I try to educate.
[1]: https://en.wikipedia.org/wiki/Cloud_seeding
Also, read the wikipedia on chemtrails: https://en.wikipedia.org/wiki/Chemtrail_conspiracy_theory
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.
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.
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.
> 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
Okay, but how does this compare to the forcing of the overall anthropogenic CO2 accumulation?
> 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
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.
> 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.
https://cdn.prod.www.spiegel.de/images/fe93cb37-2540-4fbb-a4...
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...
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.
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.
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.
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.
https://globalnews.ca/news/2934513/empty-skies-after-911-set...
Airlines are on wafer thin margins and for the longer turnaround times affecting schedules wont love it. The fact that it is a small % is worse: if you get hit you become less competitive!
Pilots workload is increased too.
Its a great technical idea but not sure how you'd get it off the ground.
In an alternative timeline with a carbon price it may work. You get x$ carbon credits for a detour. Let the planes decide if they want it.
If it was even 1% we'd surely be up in arms about how awful it looked.
Not sure how wide that would be, but the length has to be factored in too, which begs the question, how wide and long is a piece of string/cloud?
On the ground looking up the sense of scale falls apart a bit.
This was seen to be evident in global pan evaporation measurements after the essentially global flight travel bans in the few days after 9/11; I have often wondered whether the equivalent restrictions in the early days of the pandemic show it as clearly because the impacts on pollution were very striking.
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.
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.
I'm not sure they do. It's an extremely counterintuitive claim that would need to be justified, and while the author does cite (their own) paper, it sounds like the model they came up with is highly parameterised and not particularly physically validated. If it's really the case that contrails reflect more heat down than up (unlike what the scientific consensus says is true for regular clouds), then there should be an explanation for what contrail-specific factor causes this, not just "here's a pile of math equations that say it doesn't, don't ask where we got the parameters to fill them out from".
"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."
Shiny bright light goes through or gets scattered. Dull red blackbody radiation gets absorbed. Doesn't sound too counterintuitive to me, but again I'm no expert.