From the “contrails, NOT chemtrails department” comes this research that seems to exist only to make airline travel look to be bad for the planet. – Anthony
Contrails are a major driver of aviation’s climate impact
Aviation’s climate impact extends beyond carbon dioxide emissions. A new study from Chalmers University of Technology and the University of Gothenburg, Sweden, and Imperial College, UK, reveals that contrails can represent a significant portion of aviation’s overall climate cost. The study also shows that climate impact can be reduced by optimising flight routes.
In a new article in Nature Communications, The social costs of aviation CO₂ and contrail cirrus, the researchers demonstrate that both CO₂ emissions and contrail formation contribute materially to aviation’s climate impact – and that the associated societal costs differ substantially depending on weather patterns and routing decisions. They find that, at the global level, contrails account for about 15 percent of aviation’s climate impact when measured in economic terms.
After also analyzing nearly half a million flights across the North Atlantic, the research team has generated new insights that can support both industry and policymakers in guiding aviation towards more climate optimal operations. Drawing on extensive flight and meteorological data, in combination with a contrail model and an advanced climate-economy model, the researchers estimated the climate and societal cost attributable to each emission source.
“Our research provides a basis for strategies to reduce the climate impact of contrails. Our calculations can be used for optimisation of flight routes where climate impact is considered alongside, for example, fuel cost and travel time. The results give airline operators and air traffic management new tools for climate optimisation. This could bring significant climate and societal benefits,” says Susanne Pettersson, postdoctoral researcher at the Department of Space, Earth and Environment at Chalmers.
The study shows that 38 percent of flights generate contrails that have a warming effect. It also shows that it would be beneficial from a climate perspective to reduce the formation of contrails of almost all these flights through minor rerouting, to avoid contrail formation, even if this results in slightly higher carbon dioxide emissions.
“The new knowledge also provides a foundation for designing new regulations and policy instruments to reduce aviation’s climate impact. The European Commission is currently working on proposals to steer aviation towards lower climate impact, and our new study can hopefully support this process,” says Daniel Johansson, associate professor at the Department of Space, Earth and Environment at Chalmers and one of the lead authors of the next IPCC climate report.
Journal
Nature Communications DOI 10.1038/s41467-025-64355-5
But I thought models dealt poorly with clouds?
A notable effect of the 9/11 shutdown over the US was the reduction of cirrus clouds leading to a warming during the day and a cooling at night.
https://www.colorado.edu/asmagazine-archive/node/1561#:~:text=The%20tragedy%20of%209/11,clear%20impacts%20on%20climate%20change.
Or it could have been just the WEATHER.
He even admits that weather effects contrails. !!
All this goofball has is pure supposition and speculation.. zero science..
The fact he goes on about the unproven Ozone effect of refrigerant gasses shows he hasn’t researched anything , just followed the mantra. !
I just pointed out the research that was done taking advantage of the three day shutdown after 9/11, I made no ‘supposition and speculation’ about the results.
I remember the 9/11 event well and in an area which has many contrails there total absence for a few days was notable.
Regarding the Ozone depletion by refrigerant gases I discuss the research results which I am very familiar with!
… And your observation aligns with known craft, i.e. Clouds make shade, the water they use was a greenhouse gas a priori, could not reasonably be expected to raise ground temperature once condensed.
Methinks this article is trying to obfuscate the Chemtrail issue by pretending they are Scienceing contrails.
Insert that Bart Simpson meme “What an odd thing to say” as the article’s headline.
“their” total absence…. lol
“Atmospheric scientists have used these three days to measure the impact of contrail cirrus clouds, and they found that the days were two degrees Fahrenheit warmer and the nights were two degrees cooler.”
Hence about zero effect on average
It’s shocking to me that thoughtful, smart people can believe either these physical or economic “models.” These models are both so full of questionable assumptions it boggles the mind that anyone could take them seriously. We can’t forecast macro-economic phenomena 12 months in the future with +/-20% accuracy and these folks think they’re better than that. Coupling dubious economic models to dubious climate models. Wow, just wow!
It should shock you, because these people can’t connect CO2 or contrails to the Earth’s atmospheric temperatures if their lives depended on it.
Just saying it is so, does not make it so.
Where’s their evidence? None is presented. Are we supposed to just take their word for it? I guess so.
Not me. I need proof of something before I believe.
It’s not shocking – people usually go with the most popular narrative.
Then with the one that sounds the best, be it the one that is presented the best or is the most elegant.
It does not really matter how true or logical it actually is or how educated people are..
The great Watergate paradox is proof of it.
The Watergate- Scandal is by any means irrelevant.
It does not make it into the to 100 , not even the top 1000 of the major scandals in US History from an objective point of view.
It is absolutely nothing compared to all the conspiracies and lies to start wars.
Nothing compared to Iran-Contra.
it doesn’t even come close to half of the alleged Clinton-Bodycounts or Pelosis extraordinary skills.
It is nothing to Obama providing weapons to Mexican(not Venezuelan) drug cartels (fast+furious),
CiA planes with 8 tons of cocaine and a drug lord on it.
It is nothing compared to Bidens dementia,its cover up, his lawfare against political opponents,Hunters Laptop cover up,Jan6 fakery or Russia Gate.
Yet a few secret service agents in a Hotel room and a former secret service “journalist” (Woodward) are being sold as something huge, while it was one of the most irrelevant things.
Yet 99% of people, no matter their education, will instantly tell you how huge Watergate was
while it was the biggest nothing ever.
And they will say so because the media told them to perceive/evaluate it that way.
Hans Rosling observed that ignorance was greater in countries with better education.
My sense of this is that this is more speculation than science. I have watched many contrails disappear shortly after being formed. I’m retired, so I have a lot of time to sky gaze while lazing in my backyard.
“My sense of this is that this is more speculation than science.”
I think it is all speculation.
When contrails form here , looking out at Pikes Peak , they generally last quite a while . Here’s a pic w a couple of minor ones ( just because it’s pretty ) , but some days the contrails are dominate :
All these effects are too minor to be of more than ` academic interest .
“some days the contrails are dominant” perhaps? lol
Well I didn’t expect much from “Nature”, where at the bottom of the page they spruik about “nature briefing anthropocene”. I got what I expected.
Throw another “get what we expected” courtesy of an article claiming “MIT has a new plan to reduce airplane contrails and their climate impact” which links to a paper at AGU’s Geophysical Research Letters for the study titled “Contrail Observation Limitations Using Geostationary Satellites.” It’s first sentence in the Abstract claims:
Yeh, right. How many decimal places do we need to calculate how little the CO2 coming from airplanes is affecting planet-wide warming??
At one point in their anti-science gibberish they say
“CO2 emissions have long-lasting effects in the atmosphere.”
There is no scientifically measured evidence that CO2 has ANY effect in the atmosphere.
—
Then they go on about a social “cost” of CO2…
Enhanced atmospheric CO2 is a MASSIVE BENEFIT to the whole planet.
The whole paper seems to be based totally on climate mantra BovEx, and should be filed in the nearest dumpster asap. !!
I lived about 50 miles SW of O’Hare Airport back in the mid-80’s for a couple years. Contrails frequently covered most of the sky (80% contrails 20% blue sky). Contrails didn’t last more than an hour or so but they were immediately replaced all-day-long (most visible in evenings). High-altitude wispy thin clouds are credited with being a significant contributing component to global warming.
We will soon be hearing from the IPCC that with “high confidence most of the warming at commercial airline flight elevations is anthropogenic in origin ( 0.2C – 0.5C warmer). It’s worse than we thought, increase regulations and send money for needed additional research.
Only by the ignorant and gullible. Anything that reduces the amount of radiation reaching a thermometer results in cooling, not heating. About as stupid as believing that adding CO2 to air makes thermometers hotter!
Agree, but most people are ignorant and gullible about all things climate.
It depends. I was sitting on a boat on Lake Powell just downlake from Bullfrog Marina one summer day. It was clear and windless. Numerous jets passed overhead and left behind their trails. There was no upper air movement to be detected. As the hours passed, I watched them expand until much of the sky was filled with the clouds they had apparently seeded. It was definitely not clouds that moved in, as I had watched them simply grow.
Now, Lake Powell is a large reservoir in the middle of the desert with a high evaporation rate during summer, such that it certainly provides a ready source of water vapor to the cooler air aloft, and it may be that clouds would have formed absent the aviation input, but the clouds definitely appeared to grow from the contrails and not independently of them.
Interesting observation (thanks!) . . . but I’ll just note that the odds of evaporated moisture from Lake Powell rising vertically upward to an altitude range of 30,000 to 40,000 feet— where long-range commercial aircraft typically cruise and where jet contrails are also likely to form with the right range of atmospheric conditions (temp and moisture content)—is very UNLIKELY due to such air being displaced horizontally by upper air currents, especially the “jet stream” over North America that typically is found in the altitude range of 20,000-30,000 feet.
I agree. Just threw the possibility in, as remote as it is.
But you don’t know, do you?
Cloud formation is chaotic, dependent on several factors, and not clearly understood. All in all, skilfully predicting cloud formation and evolution is very UNLIKELY.
Your opinion is LIKELY as worthless as mine, but feel free to convince others that my opinion is wrong.
From the abstract in Nature: “ While uncertainty is considerable, our findings suggest that carefully implemented operational contrail avoidance could offer climate benefits even when the social cost of additional CO₂ emissions is considered.”
In other words, “While we have considerable uncertainty that it would be at all helpful in any way, we recommend a complete disruption of air travel which would lead inevitably to the destruction of the air travel and commercial air transport industries.”
Uh. . . no.
From the linked paper –
Well, gee. At night, when the surface is cooling, it’s implied that temperatures are rising – “warming impact”. During the day, they might create warming – or cooling.
The researchers don’t know, and don’t care.
What a pack of fools.
Just another piece of pseudoscientific rubbish published by Nature Vanity Press – “Pay us and we’ll publish anything.”
“Just another piece of pseudoscientific rubbish published by Nature Vanity Press”
Yep.
Global warming saves lives.
I just did some checking–if altitude and RH are held constant, then contrails are more likely to form from an airliner flight in colder air than in warmer air. Hence if the air is too cold rather than too warm, contrails will form, acting like a self-corrective measure protecting against atmospheric cooling if the thin wispy cloud retains some atmospheric heat–you know, provide some 0.02 to 0.04 degrees of warming measurable with thermometers graduated in whole degrees (0.5 degree precision).
A also noted that last week in Watson Lake Yukon the temperature was around -48C for much of the time. Plus, since the Cassiar mine closed, there are no more regular airliner flights into Watson Lake.
Put all this together, and the indications are that contrail-forming airliner flights can prevent dangerous global cooling. Where should I post my address so someone can send me a grift–I mean grant–check for more of this valuable insight and research?–because of course I need to develop this idea further.
If climate alarmists needed useful idiots.. I need to bite my hand!!!
“This result shows the increased cirrus coverage, attributable to air traffic, could account for nearly all of the warming observed over the United States for nearly 20 years starting in 1975″
http://web.archive.org/web/20041210102401/https://www.nasa.gov/centers/langley/news/releases/2004/04-140.html
There is a plethora of evidence pointing out most of the warming that is blamed on CO2 (and other GHGs), is actually because of contrails. That whole story is burried by “consensus science” because it is obviously not helpful for their agenda.
And then we have the “critical side” assisting the “consensus side” in every way possible. Well.. I am just speechless!
“This result shows the increased cirrus coverage, attributable to air traffic, could account for nearly all of the warming observed over the United States for nearly 20 years starting in 1975″
I thought the reduction in cloud cover accounts for the rise in temperatures since 1975, or so says NOAA.
This Nature “study” claims the opposite. Somebody is wrong.
Your logic is backwards. For proper approved climate science, you must start with the assumption that all change is bad. You then use a model to show that the man-made activity that you are studying (in this case, flying) changed something. Mission accomplished. One caveat: only if you can get a grant for it.
What line of argument is the bigger threat to the CO2 narrative???
Model work from Imperial College!
Just what we don’t need! 🙂
I recall bits from Google, some years ago, for an AI|deep-learning project|challenge to identify con|chem-trails in sat-images, and B.Gates talking about AI to ‘optimize’ (i.e. control|decide who can travel where|when|how) flights – and here we’re, the starting drum beat of just on-time propaganda for the masses and ‘decision-makers’ …
Water vapor???
I thought that contrails reflected some of the sun’s energy back into space, reducing naturally occurring “global warming”.
Maybe they should concentrate on global warming caused by CO2 from human respiration. And racehorses. And the various herds on African plains.
“The horror. The horror.”
Just wait until hydrogen-fueled aircraft start to dominate the skyways. /sarc
Say “Hindenburg” five times fast!
“The study shows that 38 percent of flights generate contrails that have a warming effect.”.
Sorry but I didn’t read on, so maybe I missed where they deal with the whole picture, but that statement on its own is a cherry-pick. 62% of flights don’t warm, and even more importantly, the 100% study done after 9/11 showed no overall temperature change, all it showed was nighttime and daytime changes that balanced each other out. And that could all be consistent with 38% that warm.
The overall impact of contrails can be quantified in economic terms: $0. It would seem to be an exercise in futility for airlines to spend money trying to reduce that level of damage.
While living in the Netherlands in the early 1950s, I attended an air show at an Air Force base.
The sky was solidly overcast, so our expectations of visuals were low.
But, after jet fighters had been flying below the clouds, the hot exhaust air rose and a circle of blue sky, about 4 miles in diameter, opened up, and stayed open as long as the jet fighters were flying.
I think the huge airline traffic near airports and heat release near urban areas definitely affect the weather on a long-term basis, i.e., the climate.
Worldwide, such heating greatly exceeds any effects of CO2, which is needed for growing flora and fauna, reduce desert areas and better feed 8 billion people
This article fails to account for the emissions of water vapor in the tropopause as a gas, and how the dwell time. As radiative property in the lower stratosphere, and emission rate of 95+ billion gallons per year, at current rates, must have a considerable radiative effect on the surface. Contrails are of no significance, when the ice crystals sublimate the H2O remains for some number of months.
The timeline below, suggests that the climate somewhat ebbed and flowed with solar activity and the logarithmic increase of H2O emissions from aviation starting in the 60’s has created a linear warming trend. The Warming around WWII was likely caused by over a million B24 & B17 flight in the stratosphere over the English channel. The Aksa eruption was very wet and very north, and SST has a similar signature to the HT effect.
but contrails don’t poison people
Ah these “experts” (as how Feynman described science as the belief in the ignorance of experts) are way behind in terms of altering flight paths to avoid contrails. This practice started in WW2 and continues to this day in modern air forces, where you simply do not want to visually broadcast your strike aircraft to ground missiles by presenting contrails. So they use weather charts to accurately predict where contrails will form and avoid those regions when going into battle.
As to the attribution nonsense, I wholly do not believe their climate/economic impact bull chips.
Facts: For every kilogram of JetA fuel burned, we add 3.48 kg of Oxygen, and the products of combustion are then 3.1 kg of CO2 and 1.38 kg of H2O.
Now a Boeing 777 burns 6400 kg of JetA per hour at cruise altitude, meaning it emits 19,840 kg of CO2 per hour, and 8,832 kg of water vapor per hour. That is 2.45 kg per second of water vapor emission. And it is moving at 257 meters/second. The two exhaust nozzles of the engine cores are roughly a total of a square meter. So 2.45 kg of water vapor is spread out over 257 cubic meters leaving a density of 9.53 grams water vapor per cubic meter.
However this does not account for the high pressure of the engine core exhaust. The 777 engine has an overall pressure ratio of 45, and the air at 40,000 feet is roughly 3x less dense than sea level, so the water vapor density of the exhaust, within a few tens of meters behind the exhaust is then 0.071 grams per cubic meter. (you can empirically verify this rapid expansion by observing planes and their contrails – within a short distance behind the plane the contrails expand to 1-2 times wider than the plane’s wingspan)
Normal air at this altitude is roughly 0.001 g/m³. So yes contrails can form. But they only form when the humidity is very high (higher water vapor density). In fact it needs to be super saturated for contrails to appear. Otherwise this extra water vapor simply diffuses into the extremely dry air at flight levels. (note 100% humidity at 40,000 feet amounts to 0.18 g/m³ so contrails would form with RH of about 40% at this altitude)
Is it worth diverting flight paths to avoid areas of super saturation for commercial aviation. That is doubtful or debatable. As they point out it will use more fuel and deliver more CO2. But CO2 is not the climate control knob, water vapor is 50-80 times more of a “greenhouse” factor than is CO2. So their “solution” is to pump more CO2 and H2O by making flight routes longer….
“The social cost of aviation…”
OK. Let’s balance it with the social and economic benefit of aviation. Oh. The benefit significantly outweighs the cost making us wealthier. Good.
The new “study” from Chalmers University of Technology and the University of Gothenburg, Sweden, and Imperial College, UK, published in Nature Communications, is as absurd as it is sophomoric.
Among the excerpts of the study quoted in the above WUWT article:
“Drawing on extensive flight and meteorological data, in combination with a contrail model and an advanced climate-economy model, the researchers estimated the climate and societal cost attributable to each emission source.”
Ahhh . . . of course, models . . . even an “advanced climate-economy model”, no less . . . but no mention of how they were calibrated to reality . . . IF they were calibrated at all. And what, exactly, determines both “climate” and “societal” costs” in any given model?
Perhaps there should be an accounting for the climate and societal benefits that are more likely than not to offset all asserted costs . . . such as:
— the actual net decrease in solar insolation warming* due to the fact that jet contrails are bright white and reflect incoming solar radiation (if anything creating a very slight increase in atmospheric albedo at high altitude, and thus contribute to global cooling but not to global warming)
— the jet exhaust CO2 (as revealed by the presence of jet contrails which form under certain conditions from water vapor—NOT CO2—and soot particles present in the jet exhaust and the low ambient temperatures at high altitudes) being a plant food that has helped contribute to the scientifically-acknowledge “greening of Earth” that has occurred over the last 50 or so years
— the benefits of jet air travel that enable rapid world-wide transport of emergency SAR and medical personnel, medicines and vaccines, medical equipment, shelters, food aid, communications gear, etc. in times of man-made and natural disasters
— the benefits/convenience of world-wide air travel; over one billion people travel each year by jet aircraft for business or pleasure
— national security: almost all nations of planet Earth employ jet aircraft to maintain their military security against foreign threats, thus stabilizing their economies . . . please put a benefit cost on that!
Finally,
” ‘The new knowledge also provides a foundation for . . .’ says Daniel Johansson, associate professor at the Department of Space, Earth and Environment at Chalmers and one of the lead authors of the next IPCC climate report.”
Well, there you have it . . . the smoking gun.
If Nature gave this “study” any peer-review prior to publication, it must have been tantamount to spell-checking.
*footnote:
“For a larger spatial area around the flight path, we find that the contrail cirrus outbreak is warming in the early morning and cooling during the day.”
—Observations of microphysical properties and radiative effects of a contrail cirrus outbreak over the North Atlantic, Z. Wang et al., 06 Feb 2023 (free download at https://acp.copernicus.org/articles/23/1941/2023/ )
These institutions need their grant funding revoked and the people involved fired for wasting our time, money and resources.
The latest I heard was that contrails cool the surface due to them reflecting direct sunlight back into space? Which is it?
I recall reading the IPCC report on aviation which implied that it was looking for fault with aviation. The report said that no direct evidence could be found linking aviation but that it was calculated that contrails would heat the surface because the contrails would reflect surface radiation back down. Subsequently another report asserted that aviation CO2 was twice as powerful at warming at altitude and then it was four times as powerful, even while there are more than 50% less CO2 molecules per volume at 30,000ft.
All will be explained once they find the missing heat blob.