Two links about "stratospheric aerosol injection" from mainstream sources.
"The Advanced Research and Innovation Agency (ARIA) - a government backed body - is funding nearly £60m that could allow real-world experiments, including in the UK.
"As part of the Exploring Climate Cooling programme, projects in Solar Radiation Modification (SRM) will involve trying to thicken Arctic sea ice and make clouds more reflective."
https://www.bbc.co.uk/weather/articles/c5ygydeqq08o
So there are papers. There are studies on tons and tons of things. One of the things you learn really studying science is that there are always papers, and you really have to immerse yourself in a field to see what’s actually happening.
People who believe in chemtrails need to prove that the it’s being done, is being done at industrial scale (not just a few one off experiments), and that this is harmful to human health or the environment.
Ocean fertilization to soak up CO2 has been extensively studied and in that case there are documented experiments, but we are not doing it at scale… mostly because nobody wants to pay for it and because we are not 100% sure the CO2 will actually be sequestered. There’s also some concern about side effects on ocean ecosystems.
A lot of things get studied.
Of course the real conspiracy I keep hearing is that this is some kind of mind control thing. Why? Even if that were possible, why bother when you can mesmerize humans at scale with mindless slop scrollers like TikTok and program them like a zombie army. Much cheaper and done 100% in the open.
I've never taken much of an interest in the chemtrail thing, but it does seem funny that governments are proposing to do more or less the same thing they denied doing!
I can't see this being the answer though. Maybe I'm wrong, but it wouldn't be the first time environmental measures have proven destructive. Some of the most invasive pests have been brought in to control a less invasive ones e.g. cane toads in Australia. The road to Hell is paved with good intentions.
It states that half of aircraft pollution is from contrails made of aircraft soot.
I’d like to see the literature and discovery of aircraft soot.
As an engineer who has built aircraft, I find this fascinating. I would like to measure my amount of soot. How does one go about measuring how much soot I have?
Obviously if my exhaust ports are black that’s bad but I’m genuinely curious about this as I’ve always assumed “black smoke bad, white smoke ok”. As for contrails, disturbing the atmosphere is going to cause some freezing (clouds) at that altitude, at that temperature. How do you suggest we mitigate that? Fly lower and burn more fuel? Fly less and tell people to take the train or that their package will arrive next week?
It does not state that half of aircraft pollution is from contrails. It says half of the climate impact of aviation is from contrails. Soot can have other effects and cause pollution in other ways such as reducing air quality but I suspect that is very minimal compared to other industries.
The guide presented by the map gives a very good explanation on how contrail formation can be mitigating by altering the course of flights to reduce the formation in areas where it will have the most impact. This is based on a recent study that showed contrail avoidance could be one of the most cost-effective methods of reducing warming that we know of.
>The CO2 emitted by aircraft only causes about half the climate impact of aviation. The other half comes from contrails— artificial clouds that are created by soot in the engine exhaust.
Then what does that mean?
I find it strange. Clouds happen naturally. Contrails are mini clouds (literally a cloud chamber), are we saying that all those “chemtrails” are pollution?
Or are we saying the unspent fuel particulate inside that they formed around is?
This is where this bizarro science is going off the deep end for me. As any object traveling through the atmosphere at that altitude, disrupting air, is going to form condensation and cloud trails. The more moisture in the atmosphere, the more trails. Sure there’s a little bit of unspent kerosene particles but hardly enough to even be a glycerin on a well working engine.
Are we suggesting changing flight routes and wasting more fuel (which pollutes more) to protect the ground from these 0.0000001% reduction in light cloud trails? Seriously. I want to know the science behind how this plays out.
I’m all for shutting down the black exhaust engines and cleaning up how we produce thrust. I’m all for that. This argument that clouds cause pollution is just wacky.
What about wingtips. Those cause trails (though not as pronounced as the engines turning at 12,000rpm), those contain no particulates and yet, they exist. Atmospheric science can explain a lot of what you see at 30,000ft (10,000m). This all sounds like NIMBY science posturing and pseudo-science to me.
> I find it strange. Clouds happen naturally. Contrails are mini clouds (literally a cloud chamber), are we saying that all those “chemtrails” are pollution?
Estimating radiative forcing is about measuring relative to a baseline. Here, the baseline is a world with no contrails. When you introduce contrails, you're introducing cloudy volumes predominantly made of ice crystals and occurring very high in the atmosphere. On the balance, these clouds re-emit more long-wave radiation (e.g. what' emitted by the Earth's surface) than they allow to escape the atmosphere.
Hence, these clouds have a small but positive net radiative forcing - meaning that aviation, by the way it leads to contrail formation, has at least this small radiative forcing on climate.
> As any object traveling through the atmosphere at that altitude, disrupting air, is going to form condensation and cloud trails. The more moisture in the atmosphere, the more trails.
Actually - it won't. We rigorously started studying contrail formation back in WWII when meteorologists tried to anticipate when bomber flights returning from mainland Europe might induce contrails and leave a path for intercept fighters to follow and shoot them down. As the science and understanding of vertical atmosphere thermodynamic structure and cloud microphysical structure has advanced in the ensuing 80 years, we have a much better understanding of when contrails are likely to form, versus when they aren't.
But don't take my word for it. Look up at the sky any time you hear an aircraft - sometimes you'll see a contrail, sometimes you won't. Contrails aren't a given when a jet flies high in the atmosphere.
(that's actually the entire basis for the Contrails/DeepMind team's work - avoid areas where contrails _are_ likely to form, to avoid that radiative forcing from the first part of this comment)
> Are we suggesting changing flight routes and wasting more fuel (which pollutes more) to protect the ground from these 0.0000001% reduction in light cloud trails? Seriously. I want to know the science behind how this plays out.
The science is pretty well developed at this point. You'd probably hit it in an undergraduate-level physical meteorology class. The missing detail that the Contrails team helped solve was improving forecasts of the key parameters involved here from weather models.
The whole point is that this is _another_ lever that flight planners could use to optimize their route planning. It's just one factor. It has trade-offs - although those trade-offs aren't always net negative (e.g. it's not a given that the "less contrail-y" route is also the "more fuel burn-y" one).
Finally some science, ok cool. So we're basing this on the baseline of no contrails what-so-ever. We measure the radiative photons? of the light refracting? through it and see it's long-wave radiation channeling properties scatter it rather than allow it through to relieve the earth's heat?
As for contrails, if they're likely to form in certain areas and not others, what's that coefficient? is it the moisture content? is it the jet fuel mixture? Since you say the Contrails program helps predict when these might occur, is that data being used to alter cruise paths?
It's been 20 years since I was a student at College so forgive me when I ask these questions. My grandfather flew bombers and my father flew fighters so I've known about exhaust and pollution from aircraft for a long time. I know the older aircraft pollute and the contrails from bombers (my grandfather had some stories) were an awful mix of frozen water vapor and diesel exhaust. Modern commercial jets are a lot more efficient.
Any route (with the exception of the SIDS and STARS) is charted across airways to the most direct route possible. Right?
The link to the paper I gave is the latest research on contrails and the potential effect of contrail mitigation and answers all the questions you have asked here. The video I gave boils all that information down into an easily digestible format. It honestly baffles me that you start your reply with "Finally some science" when the very same information was already provided to you. If you want to reply to my comment without digging into the links I shared then you should specify that you haven't had a chance to look into them.
> Finally some science, ok cool. So we're basing this on the baseline of no contrails what-so-ever. We measure the radiative photons? of the light refracting? through it and see it's long-wave radiation channeling properties scatter it rather than allow it through to relieve the earth's heat?
There are many different avenues you could pursue to estimate this, with different degrees of complexity and they all boil down to a radiative transfer calculation. You could start with an idealized, single-column model using a very simple approximation like a 2-stream approach, crudely parameterizing how a few bulk properties of a cloud in the column would influence the estimate of radiative balance at the top of the atmosphere. Such a model would let you explore a huge variety of factors.
To get more into the world of "real climate", you'd eventually scale up to an atmosphere model with a more complex 3D radiative transfer scheme, probably with more complex cloud microphysical representation and interactions with radiation. This still lets you do idealized experiments.
The next step up, you'd do what the DeepMind and Contrails teams have done, which is to use a standard Earth System Model ("climate model"). That just builds the complexity, and allows you to study realistic scenarios with counterfactuals (e.g. with or without additional contrail formation due to aviation). It's still going to be parameterized in some sense.
Ultimately, we'd look at real-world data top-of-atmosphere radiative estimates, which we conveniently measure from a variety of satellites (CERES would be the most well-known one). The problem is that we can't study the counter-factual very easily in the real world. We get a few isolated cases (like the aviation pause over CONUS after 9/11, or the global decrease in aviation during COVID), but there's so much inherent noise (from weather) that it's hard to infer any causality; you'd likely end up using that climate model from the last part to simulate the counterfactual in a weather scenario nudged to reproduce the real-world observations you have.
This would make a great Masters thesis, or maybe a slice of a PhD, but it's not much more complex than that.
> As for contrails, if they're likely to form in certain areas and not others, what's that coefficient? is it the moisture content? is it the jet fuel mixture? Since you say the Contrails program helps predict when these might occur, is that data being used to alter cruise paths?
It's the ambient thermodynamic and kinematic parameters. Namely, background water vapor and temperature, combined with local kinetic energy in the form of turbulence that you need to drive very local supersaturation. Given those parameters, different distributions of gases and particulates emitted from a jet engine may be more or less effective at nucleating ice - if the conditions are even right to do so.
It's worth pointing out that it's _very_ hard to capture these background conditions in weather models, hence why a major part of the DeepMind/Contrails project have been to use machine learning to try to constrain background circulation patterns most consistent with contrail develop as evidenced by high-resolution remote sensing and imagery. Some of the earliest work they did was to use these types of tools to generate data that allow us to better parameterize contrail formation in numerical weather/climate models, which is why they're able to turn this into a predictive and actionable problem.
Otherwise, there's an 80-year literature on this topic. I encourage you to read it. Kärcher's review paper in Nature in 2018 is a good starting point (https://www.nature.com/articles/s41467-018-04068-0).
> Any route (with the exception of the SIDS and STARS) is charted across airways to the most direct route possible. Right?
I'm not an expert in aviation route planning, but from personal experience I know that many other factors come into play with routing (namely avoiding weather, limiting time spent extremely remote / far away from airport or other infrastructure, traffic / network congestion, etc).
Fly less. Is waiting a week for a package really that big of a deal? Is traveling less really that much to ask?
It’s totally ok to be skeptical of the claims. I can’t make a judgement on them as I know even less than you might. But that’s not a reason to doubt that human’s environment impact matters and that maybe part of the solution is for those of us with access to 2day delivery for everything and cheap flights live a teeny bit more like those who don’t.
There is a big anti-tourism movement being built up across the world which is also being pushed by mass media. In Barcelona and Venice this has turned physical in a few instances. Flying is going to be made more expensive in the near future, I've no doubt of it. The environmental lobby will call for it.
By the way, I have not flown for over a decade. I can't stand airports...
lol thanks for saying this. "Travel" and "dogs" make up a crazy amount of dating profiles. Like 60% maybe? It's nuts. It's really weird.
then you look at most of their profiles and it's the same handful of tourist photos or them paying to take a photo, basically. travel is just another status symbol thing to a lot of people. they do the same things they see on social media. it's weird. it's just another way of showing how much money you can spend on frivolous* stuff. "30 countries by 30" and stuff like that.
the dog version of it is huskies. every one has a husky in their apartment. there are like 3-4 breeds that every woman in a city/urban area has. so weird.
*not saying travel is frivolous. I'm saying the modern stereotypical version of it is very conforming and repetitive.
the annoying thing is if someone were to ever say, in the real world, that maybe this version of travel isn't worth the damage to the environment, they would most likely get labeled an asshole or something. a "downer" or someone who is a "hater", or they are "ruining the vibe". more and more often "the vibe" is just an excuse to engage in crazy excess consumption that we label as "self care".
lol sorry to go off on this. it's just so weird how we've twisted these things around as a culture/society.
It is easy to suggest to fly less but it is going to be impossible to convince society where core values include agressive "extra" consumption, which in turn is the backbone of the world's current economy. Flying is one of top "extra" consumption types out there. I know many people are trying to convince people of that, but the society is moving in the opposite direction - bigger cars (both us and eu), more travel. Maybe arguments used currently are not convincing enough? I mean, sure, keep trying and you will obviously reach a certain 0.00x% of the population, but that's not really going to make any difference
Just tax everything the amount it costs to clean up the pollution it causes, then use that money to clean up the pollution, now everything will have the correct price including externalities
The general point here is that your individual behavior as a consumer likely doesn't impact this mechanism. An aircraft doesn't skip a flight just because you waited a week to go on vacation. Aviation infrastructure is something of a fixed-cost which would likely only respond to systemic changes in travel demand, economic impacts on maintenance or fueling, or possibly some other form of regulation (e.g. a penalty for inducing contrails).
but contrails are not made of soot, where I define soot as dark unburned carbon, contrails actual are made of water. There is also a highly likely chance I am being to literal and the word choice of soot was a bit of poetic license on the part of the author.
As a bonus consideration it might be better if they were made of soot, it would be ugly but water vapor is a tremendous greenhouse gas, several times as potent as CO2, soot blocking the sun might have more of a neutral effect, And related, we worked hard to get sulfur out of our fuels but sulfur dioxide turns out to be a negative greenhouse gas, it has a net cooling effect, I am not saying we should deliberately add sulfur back in, the downsides are too great, but it is an interesting bit of irony.
Sure, but water vapor doesn't spontaneously transition to a liquid and accrete onto surfaces - there needs to be a super-saturation of water vapor, and given the temperatures of jet exhaust, that's not trivial to achieve. However, the super-saturation needed for water vapor to deposit onto surfaces as ice is much lower, hence the preference for ice crystal nucleation.
> As for contrails, disturbing the atmosphere is going to cause some freezing (clouds) at that altitude, at that temperature. How do you suggest we mitigate that? Fly lower and burn more fuel? Fly less and tell people to take the train or that their package will arrive next week?
Here are some highlights, in case the paywall is a problem for some.
First, how much do contrails matter?
> This cirrus-forming phenomenon could account for around 35% of aviation’s total contribution to climate change—or about 1% to 2% of overall global warming, according to some estimates
> A small fraction of overall flights, between 2% and 10%, create about 80% of the contrails. So the growing hope is that simply rerouting those flights could significantly reduce the effect, presenting a potentially high leverage, low cost and fast way of easing warming.
Breakthrough Energy, Google Research, and American Airlines conducted a test:
> They employed satellite imagery, weather data, software models, and AI prediction tools to steer pilots over or under areas where their planes would be likely to produce contrails. American Airlines used these tools in 70 test flights over six months, and subsequent satellite data indicated that they reduced the total length of contrails by 54%, relative to flights that weren’t rerouted
Avoiding the contrail prone regions would use more fuel, so the question is how much would it cost to avoid those regions?
> A new study published in Environmental Research: Infrastructure and Sustainability explored this issue by coupling commercial tools for optimizing flight trajectories with models that simulated nearly 85,000 American Airlines flights, both domestic and international, under various weather conditions last summer and this winter.
> In those simulations, the researchers found that reducing the warming effect of contrails by 73% increased fuel costs by just 0.11% and overall costs by 0.08%, when averaged across those tens of thousands of flights. (Only about 14% of the flights needed to be adjusted to avoid forming warming contrails in the simulations.)
There are also a couple of other factors to consider, such as:
> There are also some thorny complications that still need to be resolved, like the fact that cirrus clouds can also reduce warming by reflecting away short-wave radiation from the sun.
> The loss of this cooling effect would have to be tallied into any calculation of the net benefit—or, perhaps, avoided. For instance, Shapiro says the initial strategy might be to reroute flights only during the early evening and night, which would eliminate the sunlight-reflecting complication.
Another one is the the increased fuel will add to CO2 to the atmosphere. CO2 stays in the atmosphere a lot longer than water, so it is possible that reducing contrails would be a net positive in the short term but a net negative over the long term.
Are there other sites that can suggest how much of an issue it is, and how much flight plan tweaking could improve this.
Remember kids a 1° C rise in temperature can mean 7% more water vapour in the air, and with water vapour being a greenhouse gas itself this can cause heating and holding yet more water.
They definitely increase the cloud cover where I live. Very noticeable, you can often see which clouds were created by them... And that's without the conspiratorial stuff.
I'm out of the loop, didn't the government admit this stuff a few years ago?
I was at a presentation in Croatia recently about weather modification in Yugoslavia. This is considered public knowledge there. When Yugoslavia fell apart, Croatia was no longer permitted to engage in weather modification.
The main method discussed was the use of small rockets. It was used for agricultural purposes.
The problem is the unsubstantiated logical leap from "weather modification is possible" to "contrails behind commercial aircraft are secretly dispersing chemicals in order to control weather".
If I was an evil government figure trying to secretly control weather, there are better ways of doing that (e.g. drones, rockets) than orchestrating a conspiracy that requires hundreds of thousands of people to stay quiet for decades.
I would however recommend testing it on a slower internet connection and a lower end device. Because I was spending 90% of my time in the "loading data" phases, and once the intro was done, the thing ran at one frame per second and I was not able to use it. (I have 5G and I bought my phone last year.)
Thanks for the feedback! We have done all the performance optimization we can in its current manifestation.
We're in the process of refactoring the models that support these visualizations, so we hope to make it more performant in the near future. Hopefully end of this year.
The team behind this is world-class. Among other things, they have developed a python library that could be used to model contrails in your own projects.
From the "about" it seems that the data is from atmospheric models based on flight paths. However, it would be cool if the data could be inferred from satellite sensing.
Hi all - very grateful to see this posted here. I'm the director of this project and would be happy to answer questions.
We are seeking a high level full stack engineer to join the team to work on infrastructure for this and other efforts. Please reach out if interested - info@contrails.org
Water vapour absorbs the thermal radiation (heat trying to escape earth) better than it absorbs sunlight (heat trying to enter earth). Therefore, the more water vapour in the atmosphere, the stronger the greenhouse effect.
They don’t cause net warming, it’s transient. If we stopped flying tomorrow it would go away quickly. But we keep flying.
But even with that the amount of warming this continuous effect creates is quite small and negligible compared to greenhouse gas warming and isn’t really worth talking about.
I think this link hit HN in part due to the new Simon Clark video on contrails which mentioned it. Simon discusses the claim that contrails can be avoided for a small fuel penalty, reducing the overall effect on climate change a given flight would have. Apparently some airlines are already exploring this and Google includes contrail impact estimates on their flight search. So maybe it is worth talking about.
Yes, also a mushroom cloud from a nuclear blast blocks light from passing through which reduces heating on the ground whereas contrails are thin which lets light through but still retains heat below them.
I have no doubt that nuclear testing has affected the environment far more than is being let on. These experiments by their nature were classified. Who's to say they weren't a factor in helping create the ozone hole?
Below is a comprehensive list of geoengineering-related patents, compiled to the best of my knowledge. Based on the language and scope of several of these patents, their stated purposes do not appear to be inherently human-friendly in any form as the language escalates from weather influence to planetary irradiation, artificial plasmas, relativistic particles, atmospheric weapons-scale energy systems, and even the generation of destructive weather events.
1. System and Method for Irradiation of Planet Surface Areas
2. Method and Apparatus for Altering a Region in the Earth’s Atmosphere, Ionosphere, and/or Magnetosphere
3. Broadcast Dissemination of Trace Quantities of Biologically Active Chemicals
4. Method and Apparatus for Creating an Artificial Electron Cyclotron Heating Region of Plasma
5. Method and Apparatus for Triggering a Substantial Change in Earth Characteristics and Measuring Earth Changes
6. Planetary Weather Modification System
The fact that someone has filed a patent doesn't mean that they have a workable idea, only that they can formulate and illustrate said idea and that it doesn't overlap with something that already exists.
We know these tests only became public decades later through hearings and declassification. Given that history, it seems fair to ask how much related research or enabling tech might still be classified. Lack of a clear public link doesn't really prove there wasn't one - it may just mean it hasn't been disclosed yet.
All I'm saying is that pointing to patents as evidence isn't convincing in and of itself. Now you've brought up specific programs, which are at the very least evidence of their own existence. I think the hurdle is still massive to accept there is any kind of global-scale geoengeneering project afoot.
Remember that there are more flights during the day than during the night. When you posted this it was late afternoon in Europe, noon on the East Coast US and early morning on the West Coast. And of course it was night in Asia.
That's right! The project started at Orca Sciences back in 2021. We moved to Breakthrough Energy in 2023, and will be spinning out into our own standalone non-profit soon.
Would be great for shiptracks, too— which used to mitigate 1/3 of the warming impact of maritime shipping — until the 2022 clean fuel standards were implemented.
Two links about "stratospheric aerosol injection" from mainstream sources.
"The Advanced Research and Innovation Agency (ARIA) - a government backed body - is funding nearly £60m that could allow real-world experiments, including in the UK.
"As part of the Exploring Climate Cooling programme, projects in Solar Radiation Modification (SRM) will involve trying to thicken Arctic sea ice and make clouds more reflective." https://www.bbc.co.uk/weather/articles/c5ygydeqq08o
Paper on how "Low-Altitude High-Latitude Stratospheric Aerosol Injection Is Feasible With Existing Aircraft" https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024EF00...
So there are papers. There are studies on tons and tons of things. One of the things you learn really studying science is that there are always papers, and you really have to immerse yourself in a field to see what’s actually happening.
People who believe in chemtrails need to prove that the it’s being done, is being done at industrial scale (not just a few one off experiments), and that this is harmful to human health or the environment.
Ocean fertilization to soak up CO2 has been extensively studied and in that case there are documented experiments, but we are not doing it at scale… mostly because nobody wants to pay for it and because we are not 100% sure the CO2 will actually be sequestered. There’s also some concern about side effects on ocean ecosystems.
A lot of things get studied.
Of course the real conspiracy I keep hearing is that this is some kind of mind control thing. Why? Even if that were possible, why bother when you can mesmerize humans at scale with mindless slop scrollers like TikTok and program them like a zombie army. Much cheaper and done 100% in the open.
I've never taken much of an interest in the chemtrail thing, but it does seem funny that governments are proposing to do more or less the same thing they denied doing!
I can't see this being the answer though. Maybe I'm wrong, but it wouldn't be the first time environmental measures have proven destructive. Some of the most invasive pests have been brought in to control a less invasive ones e.g. cane toads in Australia. The road to Hell is paved with good intentions.
It states that half of aircraft pollution is from contrails made of aircraft soot.
I’d like to see the literature and discovery of aircraft soot.
As an engineer who has built aircraft, I find this fascinating. I would like to measure my amount of soot. How does one go about measuring how much soot I have?
Obviously if my exhaust ports are black that’s bad but I’m genuinely curious about this as I’ve always assumed “black smoke bad, white smoke ok”. As for contrails, disturbing the atmosphere is going to cause some freezing (clouds) at that altitude, at that temperature. How do you suggest we mitigate that? Fly lower and burn more fuel? Fly less and tell people to take the train or that their package will arrive next week?
It does not state that half of aircraft pollution is from contrails. It says half of the climate impact of aviation is from contrails. Soot can have other effects and cause pollution in other ways such as reducing air quality but I suspect that is very minimal compared to other industries.
The guide presented by the map gives a very good explanation on how contrail formation can be mitigating by altering the course of flights to reduce the formation in areas where it will have the most impact. This is based on a recent study that showed contrail avoidance could be one of the most cost-effective methods of reducing warming that we know of.
https://iopscience.iop.org/article/10.1088/2634-4505/ad310c
Simon Clark did a good video on this recently:
https://www.youtube.com/watch?v=QoOVqQ5sa08
>The CO2 emitted by aircraft only causes about half the climate impact of aviation. The other half comes from contrails— artificial clouds that are created by soot in the engine exhaust.
Then what does that mean?
I find it strange. Clouds happen naturally. Contrails are mini clouds (literally a cloud chamber), are we saying that all those “chemtrails” are pollution?
Or are we saying the unspent fuel particulate inside that they formed around is?
This is where this bizarro science is going off the deep end for me. As any object traveling through the atmosphere at that altitude, disrupting air, is going to form condensation and cloud trails. The more moisture in the atmosphere, the more trails. Sure there’s a little bit of unspent kerosene particles but hardly enough to even be a glycerin on a well working engine.
Are we suggesting changing flight routes and wasting more fuel (which pollutes more) to protect the ground from these 0.0000001% reduction in light cloud trails? Seriously. I want to know the science behind how this plays out.
I’m all for shutting down the black exhaust engines and cleaning up how we produce thrust. I’m all for that. This argument that clouds cause pollution is just wacky.
What about wingtips. Those cause trails (though not as pronounced as the engines turning at 12,000rpm), those contain no particulates and yet, they exist. Atmospheric science can explain a lot of what you see at 30,000ft (10,000m). This all sounds like NIMBY science posturing and pseudo-science to me.
> I find it strange. Clouds happen naturally. Contrails are mini clouds (literally a cloud chamber), are we saying that all those “chemtrails” are pollution?
Estimating radiative forcing is about measuring relative to a baseline. Here, the baseline is a world with no contrails. When you introduce contrails, you're introducing cloudy volumes predominantly made of ice crystals and occurring very high in the atmosphere. On the balance, these clouds re-emit more long-wave radiation (e.g. what' emitted by the Earth's surface) than they allow to escape the atmosphere.
Hence, these clouds have a small but positive net radiative forcing - meaning that aviation, by the way it leads to contrail formation, has at least this small radiative forcing on climate.
> As any object traveling through the atmosphere at that altitude, disrupting air, is going to form condensation and cloud trails. The more moisture in the atmosphere, the more trails.
Actually - it won't. We rigorously started studying contrail formation back in WWII when meteorologists tried to anticipate when bomber flights returning from mainland Europe might induce contrails and leave a path for intercept fighters to follow and shoot them down. As the science and understanding of vertical atmosphere thermodynamic structure and cloud microphysical structure has advanced in the ensuing 80 years, we have a much better understanding of when contrails are likely to form, versus when they aren't.
But don't take my word for it. Look up at the sky any time you hear an aircraft - sometimes you'll see a contrail, sometimes you won't. Contrails aren't a given when a jet flies high in the atmosphere.
(that's actually the entire basis for the Contrails/DeepMind team's work - avoid areas where contrails _are_ likely to form, to avoid that radiative forcing from the first part of this comment)
> Are we suggesting changing flight routes and wasting more fuel (which pollutes more) to protect the ground from these 0.0000001% reduction in light cloud trails? Seriously. I want to know the science behind how this plays out.
The science is pretty well developed at this point. You'd probably hit it in an undergraduate-level physical meteorology class. The missing detail that the Contrails team helped solve was improving forecasts of the key parameters involved here from weather models.
The whole point is that this is _another_ lever that flight planners could use to optimize their route planning. It's just one factor. It has trade-offs - although those trade-offs aren't always net negative (e.g. it's not a given that the "less contrail-y" route is also the "more fuel burn-y" one).
Finally some science, ok cool. So we're basing this on the baseline of no contrails what-so-ever. We measure the radiative photons? of the light refracting? through it and see it's long-wave radiation channeling properties scatter it rather than allow it through to relieve the earth's heat?
As for contrails, if they're likely to form in certain areas and not others, what's that coefficient? is it the moisture content? is it the jet fuel mixture? Since you say the Contrails program helps predict when these might occur, is that data being used to alter cruise paths?
It's been 20 years since I was a student at College so forgive me when I ask these questions. My grandfather flew bombers and my father flew fighters so I've known about exhaust and pollution from aircraft for a long time. I know the older aircraft pollute and the contrails from bombers (my grandfather had some stories) were an awful mix of frozen water vapor and diesel exhaust. Modern commercial jets are a lot more efficient.
Any route (with the exception of the SIDS and STARS) is charted across airways to the most direct route possible. Right?
The link to the paper I gave is the latest research on contrails and the potential effect of contrail mitigation and answers all the questions you have asked here. The video I gave boils all that information down into an easily digestible format. It honestly baffles me that you start your reply with "Finally some science" when the very same information was already provided to you. If you want to reply to my comment without digging into the links I shared then you should specify that you haven't had a chance to look into them.
> Finally some science, ok cool. So we're basing this on the baseline of no contrails what-so-ever. We measure the radiative photons? of the light refracting? through it and see it's long-wave radiation channeling properties scatter it rather than allow it through to relieve the earth's heat?
There are many different avenues you could pursue to estimate this, with different degrees of complexity and they all boil down to a radiative transfer calculation. You could start with an idealized, single-column model using a very simple approximation like a 2-stream approach, crudely parameterizing how a few bulk properties of a cloud in the column would influence the estimate of radiative balance at the top of the atmosphere. Such a model would let you explore a huge variety of factors.
To get more into the world of "real climate", you'd eventually scale up to an atmosphere model with a more complex 3D radiative transfer scheme, probably with more complex cloud microphysical representation and interactions with radiation. This still lets you do idealized experiments.
The next step up, you'd do what the DeepMind and Contrails teams have done, which is to use a standard Earth System Model ("climate model"). That just builds the complexity, and allows you to study realistic scenarios with counterfactuals (e.g. with or without additional contrail formation due to aviation). It's still going to be parameterized in some sense.
Ultimately, we'd look at real-world data top-of-atmosphere radiative estimates, which we conveniently measure from a variety of satellites (CERES would be the most well-known one). The problem is that we can't study the counter-factual very easily in the real world. We get a few isolated cases (like the aviation pause over CONUS after 9/11, or the global decrease in aviation during COVID), but there's so much inherent noise (from weather) that it's hard to infer any causality; you'd likely end up using that climate model from the last part to simulate the counterfactual in a weather scenario nudged to reproduce the real-world observations you have.
This would make a great Masters thesis, or maybe a slice of a PhD, but it's not much more complex than that.
> As for contrails, if they're likely to form in certain areas and not others, what's that coefficient? is it the moisture content? is it the jet fuel mixture? Since you say the Contrails program helps predict when these might occur, is that data being used to alter cruise paths?
It's the ambient thermodynamic and kinematic parameters. Namely, background water vapor and temperature, combined with local kinetic energy in the form of turbulence that you need to drive very local supersaturation. Given those parameters, different distributions of gases and particulates emitted from a jet engine may be more or less effective at nucleating ice - if the conditions are even right to do so.
It's worth pointing out that it's _very_ hard to capture these background conditions in weather models, hence why a major part of the DeepMind/Contrails project have been to use machine learning to try to constrain background circulation patterns most consistent with contrail develop as evidenced by high-resolution remote sensing and imagery. Some of the earliest work they did was to use these types of tools to generate data that allow us to better parameterize contrail formation in numerical weather/climate models, which is why they're able to turn this into a predictive and actionable problem.
Otherwise, there's an 80-year literature on this topic. I encourage you to read it. Kärcher's review paper in Nature in 2018 is a good starting point (https://www.nature.com/articles/s41467-018-04068-0).
> Any route (with the exception of the SIDS and STARS) is charted across airways to the most direct route possible. Right?
I'm not an expert in aviation route planning, but from personal experience I know that many other factors come into play with routing (namely avoiding weather, limiting time spent extremely remote / far away from airport or other infrastructure, traffic / network congestion, etc).
This is why I love HN. My god man, thank you. I’ll have to look into this more.
Fly less. Is waiting a week for a package really that big of a deal? Is traveling less really that much to ask?
It’s totally ok to be skeptical of the claims. I can’t make a judgement on them as I know even less than you might. But that’s not a reason to doubt that human’s environment impact matters and that maybe part of the solution is for those of us with access to 2day delivery for everything and cheap flights live a teeny bit more like those who don’t.
There is a big anti-tourism movement being built up across the world which is also being pushed by mass media. In Barcelona and Venice this has turned physical in a few instances. Flying is going to be made more expensive in the near future, I've no doubt of it. The environmental lobby will call for it.
By the way, I have not flown for over a decade. I can't stand airports...
> Is traveling less really that much to ask?
I'm currently on dating apps and the amount of people who define their personalities by their travel habits is staggering.
lol thanks for saying this. "Travel" and "dogs" make up a crazy amount of dating profiles. Like 60% maybe? It's nuts. It's really weird.
then you look at most of their profiles and it's the same handful of tourist photos or them paying to take a photo, basically. travel is just another status symbol thing to a lot of people. they do the same things they see on social media. it's weird. it's just another way of showing how much money you can spend on frivolous* stuff. "30 countries by 30" and stuff like that.
the dog version of it is huskies. every one has a husky in their apartment. there are like 3-4 breeds that every woman in a city/urban area has. so weird.
*not saying travel is frivolous. I'm saying the modern stereotypical version of it is very conforming and repetitive.
the annoying thing is if someone were to ever say, in the real world, that maybe this version of travel isn't worth the damage to the environment, they would most likely get labeled an asshole or something. a "downer" or someone who is a "hater", or they are "ruining the vibe". more and more often "the vibe" is just an excuse to engage in crazy excess consumption that we label as "self care".
lol sorry to go off on this. it's just so weird how we've twisted these things around as a culture/society.
It is easy to suggest to fly less but it is going to be impossible to convince society where core values include agressive "extra" consumption, which in turn is the backbone of the world's current economy. Flying is one of top "extra" consumption types out there. I know many people are trying to convince people of that, but the society is moving in the opposite direction - bigger cars (both us and eu), more travel. Maybe arguments used currently are not convincing enough? I mean, sure, keep trying and you will obviously reach a certain 0.00x% of the population, but that's not really going to make any difference
The general way to affect public habits (whether it works or not) is to apply a "sin tax" to that activity.
Just tax everything the amount it costs to clean up the pollution it causes, then use that money to clean up the pollution, now everything will have the correct price including externalities
The general point here is that your individual behavior as a consumer likely doesn't impact this mechanism. An aircraft doesn't skip a flight just because you waited a week to go on vacation. Aviation infrastructure is something of a fixed-cost which would likely only respond to systemic changes in travel demand, economic impacts on maintenance or fueling, or possibly some other form of regulation (e.g. a penalty for inducing contrails).
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but contrails are not made of soot, where I define soot as dark unburned carbon, contrails actual are made of water. There is also a highly likely chance I am being to literal and the word choice of soot was a bit of poetic license on the part of the author.
As a bonus consideration it might be better if they were made of soot, it would be ugly but water vapor is a tremendous greenhouse gas, several times as potent as CO2, soot blocking the sun might have more of a neutral effect, And related, we worked hard to get sulfur out of our fuels but sulfur dioxide turns out to be a negative greenhouse gas, it has a net cooling effect, I am not saying we should deliberately add sulfur back in, the downsides are too great, but it is an interesting bit of irony.
The water is actually ice crystals and the ice crystals form around the soot.
There is also an immense amount of water vapour being produced by the combustion of a hydrocarbon.
Sure, but water vapor doesn't spontaneously transition to a liquid and accrete onto surfaces - there needs to be a super-saturation of water vapor, and given the temperatures of jet exhaust, that's not trivial to achieve. However, the super-saturation needed for water vapor to deposit onto surfaces as ice is much lower, hence the preference for ice crystal nucleation.
Night trains
What would make you say such a thing?
> As for contrails, disturbing the atmosphere is going to cause some freezing (clouds) at that altitude, at that temperature. How do you suggest we mitigate that? Fly lower and burn more fuel? Fly less and tell people to take the train or that their package will arrive next week?
See this article: https://www.technologyreview.com/2024/03/12/1089620/how-rero...
Here are some highlights, in case the paywall is a problem for some.
First, how much do contrails matter?
> This cirrus-forming phenomenon could account for around 35% of aviation’s total contribution to climate change—or about 1% to 2% of overall global warming, according to some estimates
> A small fraction of overall flights, between 2% and 10%, create about 80% of the contrails. So the growing hope is that simply rerouting those flights could significantly reduce the effect, presenting a potentially high leverage, low cost and fast way of easing warming.
Breakthrough Energy, Google Research, and American Airlines conducted a test:
> They employed satellite imagery, weather data, software models, and AI prediction tools to steer pilots over or under areas where their planes would be likely to produce contrails. American Airlines used these tools in 70 test flights over six months, and subsequent satellite data indicated that they reduced the total length of contrails by 54%, relative to flights that weren’t rerouted
Avoiding the contrail prone regions would use more fuel, so the question is how much would it cost to avoid those regions?
> A new study published in Environmental Research: Infrastructure and Sustainability explored this issue by coupling commercial tools for optimizing flight trajectories with models that simulated nearly 85,000 American Airlines flights, both domestic and international, under various weather conditions last summer and this winter.
> In those simulations, the researchers found that reducing the warming effect of contrails by 73% increased fuel costs by just 0.11% and overall costs by 0.08%, when averaged across those tens of thousands of flights. (Only about 14% of the flights needed to be adjusted to avoid forming warming contrails in the simulations.)
There are also a couple of other factors to consider, such as:
> There are also some thorny complications that still need to be resolved, like the fact that cirrus clouds can also reduce warming by reflecting away short-wave radiation from the sun.
> The loss of this cooling effect would have to be tallied into any calculation of the net benefit—or, perhaps, avoided. For instance, Shapiro says the initial strategy might be to reroute flights only during the early evening and night, which would eliminate the sunlight-reflecting complication.
Another one is the the increased fuel will add to CO2 to the atmosphere. CO2 stays in the atmosphere a lot longer than water, so it is possible that reducing contrails would be a net positive in the short term but a net negative over the long term.
Amazing visualisation, an excellent tool.
Are there other sites that can suggest how much of an issue it is, and how much flight plan tweaking could improve this.
Remember kids a 1° C rise in temperature can mean 7% more water vapour in the air, and with water vapour being a greenhouse gas itself this can cause heating and holding yet more water.
The site itself has more information. https://contrails.org/
I guess the map is posted today due to this recent video (worth a watch): https://youtu.be/QoOVqQ5sa08?si=sGK9Q9tUoFOW1QZg
I was expecting this to be a gag about chemtrails. I am glad I was wrong.
They definitely increase the cloud cover where I live. Very noticeable, you can often see which clouds were created by them... And that's without the conspiratorial stuff.
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> I am just so embarrassed on behalf of people who still think this doesn't exist and is all some conspiracy without any basis.
Downvoted for this, at the very least, and also downvoted for the fact you think you're entitled to an explanation even with your tone.
> I am just so embarrassed on behalf of people who still think this doesn't exist and is all some conspiracy without any basis.
There's plenty of basis for thinking it's uninformed or intellectually dishonest conspiracy mongering.
And please don't rant at HN.
I'm out of the loop, didn't the government admit this stuff a few years ago?
I was at a presentation in Croatia recently about weather modification in Yugoslavia. This is considered public knowledge there. When Yugoslavia fell apart, Croatia was no longer permitted to engage in weather modification.
The main method discussed was the use of small rockets. It was used for agricultural purposes.
The problem is the unsubstantiated logical leap from "weather modification is possible" to "contrails behind commercial aircraft are secretly dispersing chemicals in order to control weather".
If I was an evil government figure trying to secretly control weather, there are better ways of doing that (e.g. drones, rockets) than orchestrating a conspiracy that requires hundreds of thousands of people to stay quiet for decades.
Yeah, that's true. Besides, it would be morally wrong!
I found this extremely interesting and enjoyable.
I would however recommend testing it on a slower internet connection and a lower end device. Because I was spending 90% of my time in the "loading data" phases, and once the intro was done, the thing ran at one frame per second and I was not able to use it. (I have 5G and I bought my phone last year.)
Thanks for the feedback! We have done all the performance optimization we can in its current manifestation.
We're in the process of refactoring the models that support these visualizations, so we hope to make it more performant in the near future. Hopefully end of this year.
It literally (and repeatably) crashes Chrome on my android phone that has 6 GB of RAM. As in the entire browser closes.
EDIT: Though it's pretty cool on a powerful desktop. Maybe could benefit from performance optimization.
The team behind this is world-class. Among other things, they have developed a python library that could be used to model contrails in your own projects.
https://py.contrails.org
From the "about" it seems that the data is from atmospheric models based on flight paths. However, it would be cool if the data could be inferred from satellite sensing.
Hi all - very grateful to see this posted here. I'm the director of this project and would be happy to answer questions.
We are seeking a high level full stack engineer to join the team to work on infrastructure for this and other efforts. Please reach out if interested - info@contrails.org
Where are the rocket launches? Surely those are worth measuring as they are a daily occurrence on Earth.
I'm not following the logic why contrails cause net warming.
Why nuclear blasts - that also introduce lots of particles in atmosphere cause a cooling effect - "nuclear winter"?
Water vapour absorbs the thermal radiation (heat trying to escape earth) better than it absorbs sunlight (heat trying to enter earth). Therefore, the more water vapour in the atmosphere, the stronger the greenhouse effect.
https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_...
https://en.wikipedia.org/wiki/Greenhouse_effect
In this case I believe it's not water vapor, but rather reflection of IR from ice crystals.
They don’t cause net warming, it’s transient. If we stopped flying tomorrow it would go away quickly. But we keep flying.
But even with that the amount of warming this continuous effect creates is quite small and negligible compared to greenhouse gas warming and isn’t really worth talking about.
I think this link hit HN in part due to the new Simon Clark video on contrails which mentioned it. Simon discusses the claim that contrails can be avoided for a small fuel penalty, reducing the overall effect on climate change a given flight would have. Apparently some airlines are already exploring this and Google includes contrail impact estimates on their flight search. So maybe it is worth talking about.
https://youtu.be/QoOVqQ5sa08
The difference is that water vapour is a greenhouse gas. IIRC the net warming effect of clouds is a function of altitude.
Yes, also a mushroom cloud from a nuclear blast blocks light from passing through which reduces heating on the ground whereas contrails are thin which lets light through but still retains heat below them.
It's not specifically about logic. It is possible to model and measure the radiative effect of contrails.
I have no doubt that nuclear testing has affected the environment far more than is being let on. These experiments by their nature were classified. Who's to say they weren't a factor in helping create the ozone hole?
Below is a comprehensive list of geoengineering-related patents, compiled to the best of my knowledge. Based on the language and scope of several of these patents, their stated purposes do not appear to be inherently human-friendly in any form as the language escalates from weather influence to planetary irradiation, artificial plasmas, relativistic particles, atmospheric weapons-scale energy systems, and even the generation of destructive weather events.
https://gist.github.com/pupdogg/4e796ed1bb0d24338a3f6523e404...
Examples:
The fact that someone has filed a patent doesn't mean that they have a workable idea, only that they can formulate and illustrate said idea and that it doesn't overlap with something that already exists.
Totally agree, a patent by itself doesn't prove something was built or used, just that the idea could be described and cleared prior art.
But are you saying none of those patents are even indirectly related to publicly documented programs like:
We know these tests only became public decades later through hearings and declassification. Given that history, it seems fair to ask how much related research or enabling tech might still be classified. Lack of a clear public link doesn't really prove there wasn't one - it may just mean it hasn't been disclosed yet.All I'm saying is that pointing to patents as evidence isn't convincing in and of itself. Now you've brought up specific programs, which are at the very least evidence of their own existence. I think the hurdle is still massive to accept there is any kind of global-scale geoengeneering project afoot.
Very interesting project! The possibility of showcasing the flat planet concept was just the tip of the iceberg.
Including aspects like water pollution and health risks would add significant value to this already impressive initiative.
Thank you for sharing!
All I really learned from this is that European skies have a much higher density of flights than the rest of the world.
If the future of aviation is similar flight densities everywhere then people might actually begin to care about this topic.
Remember that there are more flights during the day than during the night. When you posted this it was late afternoon in Europe, noon on the East Coast US and early morning on the West Coast. And of course it was night in Asia.
This group is funded by Orca Sciences, which is also behind Standard Thermal.
https://www.orcasciences.com/
That's right! The project started at Orca Sciences back in 2021. We moved to Breakthrough Energy in 2023, and will be spinning out into our own standalone non-profit soon.
Would be great for shiptracks, too— which used to mitigate 1/3 of the warming impact of maritime shipping — until the 2022 clean fuel standards were implemented.
Preserving the aesthetics of the sky is reason enough to stop artificial clouds. Why would we accept such a mess?