Contrails = Aviation Smog.

‘Are there any anti-CONTRAIL groups?’ was the title of a discussion that Ray von Geezer started on 30 September 2014 on in the section ‘Open Discussion’. He wrote:
“Are there any groups who campaign against contrails rather than chemtrails? It’s something I’ve wondered about for some time but never found any evidence of, although recently I have noticed some chemtrail groups saying things like “regardless of whether you believe they’re deliberately spraying chemicals or not you should see these ugly trails are a problem”. [..] So, has anyone ever seen a group who simply just complained that otherwise clear skies were being visually “spoilt” by contrails without invoking “chemtrails”? ”
I wrote:
“Contrary to what you suggest, the main focus of my websites and is not juston the visual impact of contrails, although it appals me ‘that otherwise clear skies are being visually spoilt (without hyphens) by contrails’ .

“I do not invoke “chemtrails” because polluting the higher regions of our troposphere and creating meteorological and climatological problems is already bad enough.”

My reaction provoked a (sometimes heated and personal) discussion on in the section ‘Open Discussion’. It started on 30 September 2014 about contrails in general and more specifically about my calling them ‘aviation smog’.

Nick West, administrator of the website of, pointed to my website, calling it “the ‘Aviation Smog‘ site in The Netherlands” (that I had sorely neglected in the past few years..) After participating in the ‘open discussion’ on Metabunk, I came to the sad conclusion that it’s members accept that the air is polluted by aviation, but not that this could have any effect on weather and climate. My calling contrails ‘aviation smog’ was generally disclaimed.

As websites and blogs often disappear after a while, I use my own blog as an archive for my contributions and for a selection of (sometimes abbreviated) reactions from other participants that I found interesting or otherwise worth saving.

In the discussion on about all the typical questions and (often derogatory) remarks about contrails (= aviation smog) and my pictures and texts came into play. The complete discussion with all the contributions can be read on the website of

Balance wrote in reaction #2 to Ray von Geezers article:
Bit like complaining of traffic noise after buying a house next a motorway, I guess. Not something I’ve given much thought about.

Hevach wrote #3:
The thing about reasonable people is that they have reasonable reactions to problems. The reasonable reaction to a streak of white in a clear sky, if that just really grinds your gears, is to turn the outrage knob up to about 1 or 2. It’s up there with stubbing your toe while you have shoes on, too much cheese on your pizza, or being stuck behind an inconsiderate person who leaves their cart in the middle of the aisle at Wal Mart. People do complain about those kinds of things, but if you dedicated yourself to one of them the way chemtrail believers pursue their craft… Well, people would think you were crazy.

Steve Funk wrote #4:
The first half of the Case Orange report was devoted to the adverse impacts of ordinary contrails in Europe. It was probably a collaboration, with the chemtrailers writing the rest of the report.

Administrator Nick West wrote #7:
There’s the “Aviation Smog” site in the Netherlands, but while it does not suggest deliberate spraying, it still suggests that contrails cause drought and other more dramatic changes in the weather. The main focus does seem to be on the visual impact of contrails though.

Nick West pasted an exerpt from my website

‘The word Contrail stems from ‘condensation’ and ‘trail’. Aviationsmog (that’s what it really is) is caused by airtraffic at great heights. Each day, jetengines of airplanes dump vast amounts of water (ice), CO2, soot particles (condensation nuclei), aerosols and chemical substances. Airtraffic thus not only alters the properties of the higher regions of our troposphere but also all the regions below, right down to groundlevel. This extra layer of man-made high-altitude smog probably infuences weather, climate and the quality and quantity of thesun’s radiation that reaches the surface of Earth (“global dimming.”). Aviation-smog is responsible for more clouds, rain, drought, bigger hailstones (megacryometeors), a stronger greenhouse effect (global warming), and, maybe, even gives extra power to hurricanes. Still, aviation-smog does not get the scientific and political attention it deserves.’

Hama Neggs wrote #8 and #9:
“There has been a recent trend toward avoiding any argument about the content of the trails by focusing on the visual aspect and sun-blocking, but no dedicated groups, afaik.”
Madison has been using the term “aircraft pollution” a lot when confronting officials on the matter.

Nick West wrote #11:
Yes, but she’s a true believer in the chemtrail theory, she actually thinks the long white lines in the sky are deliberate spraying. She’s not really “anti-contrail”.

Hama Neggs wrote #12:
No, but it’s just an example of how the language being used is not descriptive of what she/they really believe. It’s a (perhaps unintentional) hedging of their argument so that it can’t be countered. Who can rightly say that the trails in the sky are not “pollution” of some sort?

Nick West wrote #13:
I think there has been some “anti-contrail” rumblings from astronomers in the past, but did not get much traction:

Content from external source:
2 March 2006
Contrails often present little more than a transient nuisance to astronomers; but when certain weather conditions prevail, they can break to look like natural clouds.
Holger Pederson, an astronomer at the Nils Bohr Institute in Copenhagen, Denmark, who has studied contrails, explained: “You can recognise the jet contrails when they are young. So you can stop your observation and then restart as soon as the contrail has passed the field of view of the telescope.
“Worse is when the contrails last for hours. Then they degrade into something you can hardly distinguish from natural cirrus clouds.”
Dr Hermann Mannstein, of the German Aerospace Centre (DLR), agreed astronomy would become more difficult, but said there was an upper limit on the contrail problem.
Contrails form where the air is highly saturated with water vapour, but will not form if the air is too dry
“You don’t clog the whole sky. You have a certain proportion of the sky, in time and space, that can be affected,” he said.
This page exist only in the archive, and has lots of broken links.

Nick West wrote  #16:
But the question here is if there are any genuinely anti-contrail people out there. Sometimes when I discuss the chemtrail theory with people who are very new to it, they end up agreeing that maybe they are just contrails, but then say “I don’t care what they are, they a messing up my sky” (or similar). But it seems they don’t really go on into anti-contrail activism. They either drop it, or go back to saying they are chemtrails:

Content from external source:
Chemtrail/contrails. I don’t care what they are. The fact is that i’ve seen many a clear blue sky turned in a hazey cloud-filled one pretty quickly. It might be done interntionally, it might not. It might be weather modification, it might just be standard air traffic.
But the truth is that this increase in air traffic is causing additional clouds to form, which in turn is affecting the weather. We are making clouds. This is weather modification whether intentional or not.

Analyst wrote #17:
Well I guess that’s the difference between the true believers & those with marketing concerns. I have seen one or two people that just seem more bothered by the aesthetic nature of contrails, but they keep bad company. How long their concerns remain purely aesthetic, I don’t know.

Hama Negg wrote #18:
But that just indicates that they think the trails are creating the weather, not reacting to it.

Nick West wrote #20:
Contrails do create cloud cover sometimes. It’s not unreasonable for people to dislike this.

Hama Negg wrote #21:
I suppose, but it gets all tangled up in the idea that the contrails created weather fronts, storms and rain.

Cmnit wrote #22:
IPCC devotes some of his efforts in the so called AIC (Aircraft Induced Cloudiness) because is a significant part of the anthropogenic causes of Climate Change, albeit a small one. Estimates say that AIC contribution is on the same ballpark of CO2 emissions from civil aviation. Good sources:

Germans are so serious about this that some proposals for Europe try to modify flight routes or heights in order to avoid ISRs (Ice Supersaturated Region) which are responsible for persistent contrails evolving in cirri.

It is also worth mentioning that at a conference of astronomers in 2002 on the topic of light pollution, contrails were discussed:
Light Pollution: The Global View. Proceedings of the International Conference on Light Pollution, Chile

Weedwhacker wrote#23:
Well. As noted, there can be occasions when contrails (due to an airplane passage in the upper atmosphere) can have a “trigger-effect” that induces further cirrus-type clouds to form in the region. However, I would argue (will need to find studies to back it up) that these cirrus clouds could very well form anyways, due to normal natural reasons.
Still….(again, another study is needed)….airplane contrails are just so “visible” that they have become a topic…”du jour”…if you will.
Certainly a LOT more polluting is occurring at ground level. (Witness many major cities in China, for instance)…..
Edit: Also, far too many times it seems that people who “complain” about contrails seem to think that they (the contrails) will somehow “fall” directly and vertically down upon them. There is a lack of understanding of how earth’s atmosphere actually works… vast it is in three-dimensions, and how upper winds affect flow patterns.

David Fraser wrote #24:
At the moment the issue of contrails is non really addressed by the major NGOs such as Greenpeace, however I expect that to change. We are looking now at the proposed expansion of Heathrow and quite possibly a few other over the next few decades and given recent studies on the effects of contrails I expect the specific protest groups like Airportwatch and Planestupid will latch onto that as a good arguing point. At the moment they mainly concentrtate on carbon emissions but I definately would be saying “Do you want to see more lines in the sky?” Now that would gain far more public support.

Weedwhacker wrote #25:
It is important at this juncture to note that an “expansion” of any specific airport (in terms of added runways, or increased ability to handle hourly traffic) is NOT related to contrails! Not directly, at least. Certainly the Air Traffic Control system and airspace that is becoming more ‘crowded’ is a slight factor…..but NOT specific airports.

David Fraser wrote #26:
Expansion is “needed” for the increase in air travel, which in itself is going to cause more contrails. People like Richard Branson are in favour of a third runway so they can open up new routes. Of course it is directly to contrails related especially given that there is an expected increase of 50% or more in passenger numbers by 2030.

Trailblazer wrote #27:
And just think of all that extra water being created by combustion! That’s got to cause sea levels to rise by a micron or two…

Chemtrail_follower wrote:
I remember seeing this a while ago [in  the issue called
‘Environmental Justice’ of Essence  (The University of Victoria Environmental Studies Student Association Periodical),
Volume 5 Issue 1 Spring 2012)]:

‘Final Boarding Call’
by Beth Bower
.. Airports have become the stage for some of the most emotional moments in our public lives. The toughest goodbyes we will ever have to say and the most magical of reunions are often played out here, amidst the duty free shop and metal detectors. But there is another drama brewing on this stage. It’s an epic one, whose global proportions transcend and knit together all of our personal stories. The actors include international corporations, carbon, technology, culture, and ultimately each of us. It is here on the public stage of the airport that we will have to face the truth about climate change and our love of flight. #at is, if we are going to have a real chance at curbing climate change, the days
of commercial !ight as we know it are over.
The reason behind this drastic declaration is a story line that we’ve all become increasingly familiar with over the past decade. Airplanes burn fossil fuels. And burning fossil fuels means greenhouse gas (GHG) emissions, which means trapping more of the sun’s heat, which means climate change. However, although related, the emissions from aviation are distinct from those of cars or home furnaces. Firstly, although the airline industry is adept at never mentioning it, there is the simple fact that airplanes travel long distances. In their latest bit of eco-PR Air Canada’s website proudly proclaims that:
Our latest aircraft use approximately 3 litres of fuel per 100 passenger/km . . . it compares favourably with the fuel efficiency of a compact car. (#e only difference: We go a little bit faster. Ok. A lot.)
What Air Canada does not mention is that those super speedy aircrafts cover distances like 11 170 km: the distance from New York to London and back again.
To gain some perspective, consider the fact that in the course of an entire year the average Dutch citizen will consume the same amount of fuel with their car that it takes to fly one passenger 10 000 km. That is, with a Dutch driver’s entire fuel allowance for the year, you could get from New York to London but you’d be kicked off the plane 1 170 km short of New York into the Atlantic. The issue here is one of scale; although fuel efficiency has increased, the sheer number of kilometres planes cover mean that they still release staggeringly high amounts of carbon.
And it’s not just carbon coming out of those jets. A myriad of GHGs result from burning kerosene. One of those GHGs is water. Oddly enough, one of the most vital conditions for life also acts as a greenhouse gas. When hot, moist exhaust rushes out of a jet engine straight into the icy upper troposphere, it crystallizes instantly. This is what forms those thin streams of exhaust that planes trace across the sky on a clear day. They’re known as contrails, and their effect on local temperature was recently revealed in an unexpected way.
In a perverse twist of fate, researchers at the University of Wisconsin were offered a golden research opportunity they never thought possible when planes were grounded for three days after September 11, 2001. While people around the world mourned, David Travis, Andrew Carleton and Ryan Lauristen got busy analyzing temperature data from 4 000 weather monitoring stations in the United States. Their results backed up what they’d long hypothesized. It turned out that with all the planes grounded, a significant increase in average diurnal temperature range could be seen. This meant that the difference between the temperature at night and during the day increased when planes weren’t in the sky. The contrails were acting like a blanket, insulating the continent from the natural decline in temperature that should occur when it faces away from the sun during the night.
Now, the fact that they got such significant results over just three days also means that contrail induced warming is a short-term phenomenon. No planes and the blanket effect disappears. But because planes are always in the sky, this short term effect is really a long term effect as far as any ecosystem is concerned.
The cumulative result of all these extra emissions is that the warming effect of a flight is more that just its calculated carbon output.
The International Panel on Climate Change (IPCC) has calculated an uplift factor to try to determine the true impact. They estimate it to be anywhere between two to four times greater than the warming effect of carbon alone. However, the science behind these calculations is still up for debate, and the IPCC warns that it is not as simple as just multiplying a given amount of carbon emissions by the uplift factor to figure
out total warming effect.
What is clear is that the climate impact of a plane ride is much more than just the sum of its carbon emissions.
The flight from Edmonton arrives, breaking my reverie. Why were these passengers up in the sky in the first place? Well, it turns out they were flying for business, for pleasure, and most often, to see family. I met a business man who flew every week for work, as well as a school teacher who rarely got on a plane — he was just there to pick someone up. But despite my head full of dark statistics,
I could hardly point a finger at the people I spoke with. After all, I’m guilty as charged. As a university student living away from home for the first time, there’s nothing as comforting as catching the sweet one hour flight back to Calgary every Thanksgiving and Christmas.
To simply stop flying appears to be a social impossibility. With the rush and globalization of our workplaces, and the scattering of our families across the map, how can we ever stay grounded? As one woman I spoke with put it, “We’d have no world!”
But what if this social impossibility is a social necessity? What if instead of viewing our need for grounding as a prison sentence, we paused for a moment and considered what would happen if we all stayed home. As an eloquent business woman at the airport put it, “maybe we all need to run around a lot less.” Perhaps if it wasn’t so easy to escape, there would be a revitalized interest in making our day to day environments more liveable. If we couldn’t go see the Louvre, we would want a thriving local arts scene and our own ways of communicating local history. If we couldn’t have destination weddings, we would want meaningful local places to celebrate. If students couldn’t fly away to university, imagine the pressure on government to provide each city with a top of the line teaching and research institution.
What all these “ifs” add up to is the possibility of cultural change. A social movement for staying put. Admittedly, I have danced around the issue of how exactly we will get there. I just don’t know. However, what I do feel more certain about is that clinging to aviation as a social necessity only reveals a profound lack of imagination. There is plenty of room to have expansive, diverse, and meaningful lives in our own backyards.
By: Beth Bower. [page 6]

Robert van Waning wrote #29:
Contrary to what you suggest, the main focus of my websites and is not juston the visual impact of contrails, although it appals me ‘that otherwise clear skies are being visually spoilt (without hyphens) by contrails’ .
I do not invoke “chemtrails” because polluting the higher regions of our troposphere and creating meteorological and climatoligical problems is already bad enough.

Efftup wrote #30:
Welcome Robert. Thankyou for providing some clarity.
You are aware of course, that whether a plane is making a contrail or not, those planes are still there, producing the same substances from their exhausts. When trails are visible, it is just a very easy way to show just how much Air traffic there is in our skies.
Have you compared statistics of how much pollution air travel is producing compared to cars/trucks at ground level for example, not to mention industrial processes?

Trail blazer wrote #31:
While what you say is true, on an aesthetic level I can see why people object to contrails. They undoubtedly do make it cloudier and will continue to do so. Estimates state that by 2050 many areas with heavy air traffic (especially the eastern U.S. and NW Europe) can expect greater than 10% contrail cover on an annually averaged basis.


Efftup wrote #32:
Oh yes, I can see the problem from an aesthetic level.

Robert van Waning wrote #33:
The pollution by airtraffic has more more effects on weather and climate than cars/trucks, industrial processes, heating of houses and buildingsd, production of electricity, etc. because of the level where during 24 hours of each day around the world aircraft dump massive amounts of watervapour and aerosols (acting as condensation nuclei). Weather is ‘made’ in the tropopause at a height of 10 – 13 km, exactly where the passenger- and freightplanes fly and burn their fossile fuel.
The effects of aviation smog on weather, climate and the Sun’s radiation are underestimated and euphemized, because nobody wants to know them. Research is too expensive and nobody is interested in the results.
On a flight from Amsterdam to Singapore a Boeing 777 takes 100.000 kilos of kerosine, I just read in a newspaper. Each day there are 30.000 flights in Europe alone..
Flying is far too cheap, because it is not taxed like any other means of transportation.

Nick West wrote #34:
But if there’s not enough research, how do you know how bad it is? The amount of water vapor added is very small compared to what is already there. So how is it affecting anything if if does not make a contrail?

Keefe wrote #35:
One or two contrails are ok, but when there are lots of them it is a kind of visual pollution – that might be what gets people started on chemtrail theories – it just doesn’t look right … for one thing [..]

Robert van Waning wrote 36#
A fair comment. Based on my knowledge of physics, meteorology, on what I have read about climate change, on my experience with weather, on my observations and on what I think is rational, reasonable and unavoidable, I think that the addition of enormous amounts of (quickly frozen) watervapour in combination with aerosols acting as condensation nuclei constitutes a major change in the higher regions of our troposphere that simply cannot be without consequences.
Also, research has been done in the past years, but not on the scale that – I think – is necessary. I myself have neglected this subject in the past years, but I especially remember the name of Patrick Minnis, an American climatologist. I have put many links to scientific reports on contrails etc., but many of them are outdated by now, I am afraid.
One effect of aviation-smog might be that it makes hailstones grow bigger. They are ‘born’ at an high altitude where there are now more far more condensation nuclei and more (frozen) watervapour than before aviation. Hailstorms cause ever more damage, because of the size and weight of the stones, that sometimes can gert bigger than golfballs. A friend of ours makes a good living removing the dents out of expensive new cars after a heavy hailstorm has hit a parking lot of a carfactory. He repairs the damage in such a way that the cars do not have to be painted anew. Have a look at these pictures:

Robert van Waning wrote #37:
In her article ‘Final boarding call’ the author, Beth Bowen [see above], writes:

“It is here on the public stage of the airport that we will have to face the truth about climate change and our love of flight. That is, if we are going to have a real chance at curbing climate change, the days of commercial flight as we know it are over.”

I think that this is true, because in the foreseeable future there is no alternative for the cheap fossile oil that aviation depends on. As a start, kerosine should be heavily taxed because of its nearing scarcity and because of the environmental impact of the way it is used.

Skephu wrote #38:
Is that only a conjecture or do you have studies to back it up? Ice crystals at cirrus altitudes grow bigger and sink, but as they reach an altitude where temperature is high enough and the air is drier, they evaporate and never reach the ground.

Robert van Waning wrote #40:
It is a ‘conjecture’ based on what I read and hear about heavy hailstorms that get more frequent, with bigger hailstones creating ever more damage. My friend who repairs the cars confirms that he is happily drowning in work.
It seems logical: Hailstones fall to the earth, but at hot weather they are lifted up again at high speeds by upward heated-up airstreams. At high altitudes with a temperature of minus 45 degrees Celsius they grow bigger by collecting more (frozen) water in an environment that has become saturated with it by the exhaust of airplanes.
Also, I think that hailstones are ‘born’ more often than before at higher altitudes because of the saturation of those regions with (frozen) watervapour and condensation nuclei by intensive airtraffic.

Trailblazer wrote #42:
There is more water vapour in the atmosphere than there used to be, @Robert van Waning, that is true. However the reason is not water from combustion: it is simply that the atmosphere is warmer than it used to be, and warm air can hold more water than cold air. That is also likely the reason for more violent storms (if indeed they are more violent, which is open to question). More energy in the atmosphere.

Robert van Waning wrote #43:
True, but I am talking specifically about the troposhere at an altitude of 10 – 13 kilometers. There the temperatures ar far below zero Celsius, but each day massive amounsts of water vapour and Aerosols (acting as condensation nuclei) are added each day by airtraffic. Tropical storms collect ever more ‘mass’ from these altitudes, thus growing in strenght, I think (‘conjecture’).

Henk001 wrote #44:
Exit conjecture and gut feeling. Enter science. A recent paper confirms that (persistent) contrails have a considerable impact on warming the climate:

Persisting contrails present the greatest impact on climate because instead of dissipating relatively quickly they linger, trapping heat beneath them. While contrails do block the sun to some extent, when they persist they also spread and become thinner, which means they don’t reflect as much solar energy away while still trapping heat.
“The net effect tends to be to warm the earth’s surface, rather than to cool it,” Carleton said.
The new research finds that in addition to shrinking the temperature range, contrails contribute to high-level cloudiness, which can contribute to warming the atmosphere.…ls-contribute-heat-trapping-high-level-clouds

Nick West wrote #45:
That makes no sense at all. Hailstones don’t form from water vapor, they form from supercooled liquid water. They form in thunderstorms which are saturated with water because they are rain clouds. The water comes from low altitudes, and rises by convection. The upper atmosphere water content has very little to do with it. The amount of water in just a single one square mile thunderstorm is more than the amount of water added by planes over the entire United States in a day.
It seems you are basing your claims on anecdotes and guessing.

Robert van Waning wrote #47:
Theories and hypotheses remain based on guessing as long as there is no scientific proof. So, should we stop guessing and worrying about developments that seem to lead to unwanted consequences?
My guess is that the upper troposphere get so saturated with frozen water vapour (condensated on soot and aerosols) that the origin of hailstorms will also be on those higher levels. Hailstones that are driven upward by convection, will meet more supercooled water on higher levels than before airtraffic reached the tropopause.

“If the relative humidity of the surrounding air at the altitude of the airplane is low, once the contrails have formed they cannot survive long as they evaporate through mixing with the surrounding air. In contrast, if the surrounding air is already above a relative humidity value sufficient for the formation of ice crystals, the ice particles in the contrails can survive for a much longer period of time. [..]
Along with the direct effect of the contrails themselves, it has been suggested that the extra condensation nuclei emitted in the exhausts might have a climatic influence once the contrails themselves have evaporated away. Their addition could cause the number of ice particles at the tropopause to increase so much that the later formation of natural cirrus clouds is made much more likely. These additional clouds can no longer be directly ascribed to the airplane emissions and hence are not included in studies of the contrail effects. The number of cirrus clouds observed in the last decades has increased however, which may be indicative of such an effect.”
(‘What role do condensation trails play in our climate?’…-condensation-trails-play-in-our-climate.html )

Robert van Waning wrote #48:
‘Blocking the sun’ is just mentioned sideways in this quote, but one of my guesses/worries is that this filtering of the sun’s radition will affect growth processes on earth. What part of the radiation is blocked and how crucial is that part for plants etc. to grow and live?
Most people who are aware of aviation smog, concentrate on its warming or cooling effect on the atmosphere. Personally, I am also worried about the ways in which affect the weather: Will it contribute to more frequent and heavier rainfall (and snow and hail) in some regions and thus to more drought in others? Will it contribute to the frequency and strength of tropical storms by giving them more mass?
(Pardon my English and my lack of proper scientific terminology. I am just a Dutchman who takes pictures of something that worries him, especially because it seems not to worry most people, including scientists, politicians, journalists and ‘weathermen and -women’.)

Trailblazer wrote #51:
Your guess cannot be right. You seem to be confusing relative humidity with absolute humidity. The air where planes form contrails is very cold and very thin – typically about -40 to -50°C and 200 to 300 millibars (one fifth to one third of sea level pressure).
Such air can hold minuscule amounts of water vapour compared to the warmer, denser air lower down. Hailstones form in cumulonimbus clouds, which contain orders of magnitude more water than even totally saturated air at flight level.
The tiny amount of extra water vapour in the air surrounding the top of a cumulonimbus cloud will not have any effect when compared to the massive amounts of water inside the cloud. Hail forms from supercooled water inside the cloud: water that is being carried up from the lower troposphere.
Also, as @deirdre points out, the limiting factor on hailstone size is the strength of the updraft. When the hailstone gets too big and heavy for the updraft to support it, it will fall to Earth. It’s not stopping growing because it’s running out of water to add, it’s stopping growing because it’s too heavy.

Robert van Waning wrote #52:
So we can all stop wondering and worrying and quietly go to sleep? Not me. I hear and read far too little about aviation smog than would be justified by the probability of undesirable consequences. In weatherprograms on radio and tv aviation smog is never called by a proper name and always euphemized as ‘sluierwolken’ (veil clouds’) like they were normal and natural and nothing can be done about this development. Smog on the surface is called smog, and quite rightly so.
The spokesman of KNMI, the Royal Dutch Meteorological Institute even had the nerve to say that on a particular day ‘there was not a single cloud in the deepblue sky’ whilst that sky in fact had been covered by aviation smog. “It’s a lobby, not a conspiracy” Tony Judt said in a different context.
‘Young’ and still small and light hailstones can be carried upward to the higher regions, where – I guess – they nowadays grow more than they did before. By the time they fall definitely because of their weight, they grow more than before as the atmosphere is getting more humid because of various reasons of which airtraffic is only one.

skephu wrote #54:
“Smog” is not a scientific term, and its meaning is not well-defined. Contrails do not differ from natural cirrus clouds very much. That’s why they are called “contrail cirrus”. The word “smog” implies lots of smoke, which contrails are not.
[RvW wrote: ‘Young’ and still small and light hailstones can be carried upward to the higher regions, where – I guess – they nowadays grow more than they did before.]
I don’t think that happens. Hailstones arise in low clouds, and they will never be carried up into high clouds.

Robert van Waning wrote #55:
We’ll see. My ‘errors’ are not more serious than your ill-based certainties. Also, while aviation smog is a wonderfully emotionally laden term, it’s not even close to accurate. Smog is a complex melange of pollutants near ground level, chief of which is ozone, a carcinogen. Contrails are more or less pure water ice at 30,000 ft. They are no more aviation smog than San Fransisco’s advection fog is marine smog.
A dictionary defines ‘smog’ as “Fog mixed with smoke and fumes from factories, houses, vehicles etc. Some big cities have a problem with smog.”
In its simplicity this is quite accurate. It says nothing that the location of this mixture should be at ground level for a correct use of the word. The term ‘marine smog’ could indeed be applied to smog originated by vessels.
Please have a closer look at my pictures on and try not to look at the stripes but at the vagues shapes between them.

Robert van Waning wrote:
The word smog does not imply a minimal amount of smoke but enough of it for water vapour to condensate on the particles. I doubt whether hailstones like shown in this picture originate in low clouds. Even if they do, on hot days they can be driven upward by strong convection winds to higher regions.
Here are a couple of links to heavy hailstorms with hailstones the size of golfballs and even tennisballs:
Huge hailstones in storms

skephu wrote:
This study suggests that hailstone diameter is expected to increase with global warming:
Change in hailstone size distributions with an increase in the melting level height

In France, the melting level height varies, during the hail season, from about 1 km in the spring to more than 4 km in the summer, and this parameter appears to have a connection with the mean characteristics of hailfalls. In fact, a large 25-year sample of hail size distribution measurements, made with hailpad networks along the southern Atlantic coast, reveals strong correlations between the melting level height and the mean hailstone number in different hailstone diameter ranges. On average, an increase in the melting level height is associated with a decrease in the number of small hailstones (5 to 7 mm diameter), has no apparent effect in the middle range (7 to 9 mm), and is concomitant with an increase in the number of larger hailstones, particularly in the 11 to 21 mm ranges. When the relationships giving the hailstone number in each diameter range as a function of the melting level height are applied to a given hailfall, an increase in the melting level height is then found to go together with changes in the total hailstone number and kinetic energy. From this observation, it is possible to estimate the potential effect of global warming on hailfalls with different hailstone size distributions. The trends in the monthly surface temperature and in the hail day melting level height observed at Bordeaux during the 1988–2012 period and the global warming projections made for the present century suggest that an increase in the melting level height of 500 m is forecast to occur in this region between 2000 and 2040. The consequences of such an increase for a standard hailfall in the region will be a slight decrease (− 12%) in the total number of hailstones, and a significant increase (40%) in total kinetic energy, but with no significant change in the hail frequency. This analysis is compared to the already observed increase in hail intensity in the area under study, and to observations, measurements, and numerical models in other parts of the world.

Henk001 wrote:
@Robert van Waning: You should try and find more scientific support for your claims. Like Skephu showed there can be a change in hail size without the contrails. Meteorologists and climatologists study a lot of the effects that contrails can have on weather and climate. If you can’t find any on the connection between hail and contrails (try google scholar) then your supposedly connection is probably not as obvious as you think, otherwise there would have been a study about that.
I personally think that Cirrus clouds (both natural and contrail induced) are not related to the formation of hail storms, because of the mechanism behind these storms, as pointed out above by several others. About this I found an illustrative site, in dutch mainly, but with a lot of nice animations (I don’t know how to copy a working animation here :():
You can always email the KNMI for questions about these things; perhaps you take them on an idea.

Robert van Waning wrote:
There is nothing wrong with expressing worries that are based on accumulated knowledge and on personal observations that seem to confirm them.
How could I possibly prove – albeit ‘somewhat’ – that aviation smog helps to make hailstones bigger and hailstorms more frequent? I think it does and you do not, without your being able to prove your opinion.
I’m going to let you slide on the misuse of the term “smog”- what you mean is “pollution”. That said, I hate to break it to you, but that pollution from planes is there whether you see the contrail or not.
Just look it up: All definitions of smog contain the combination of fog (water vapour condensation in an environment that is saturated for it) and smoke (soot, microscopic particles that act as condensation nuclei).
It seems that these drops cq crystals are hygroscopic. This would explain why those narrow contrails often grow into wide cirrusclouds. Many examples of this phenomenon can be seen on
Smog clearly is a sure symptom of pollution. What makes the pollution by planes special, is the place where most of it occurs, namely at a height of 10 – 13 km, where temperatures are around minus 45 degrees Celsius and where the original relative humidity was lower before airtraffic started raising it.

Robert van Waning wrote:
Just one page further on the website of the Dutch meteorologist Kees Floor, a graphic animation clearly shows how hailstones are constantly driven upward to regions where it is freezing hard and where they grow further until they get too heavvy:
Kees Floor wrote about my contra-contrail activities on his website and in his beautiful book about clouds:
[Henk 001 wrote: You can always email the KNMI for questions about these things; perhaps you take them on an idea.]
Since 1995, when I started taking pictures of contrails and aviation smog and expressing my theories and worries about this development in our atmosphere, the KNMI has been as sceptic about my theories as most of you are, but in the past 20 years they have been losing ground for this scepticism.

Robert van Waning wrote:
[Hama Neggs had written: The term “smog” was coined to represent a FAR higher percentage of “smoke” than is ever present in contrails. You seem to be using the term because of its emotional impact rather than any true scientific similarity.]
Originally, yes. But meanings evolve. Houses are no longer heated with coalfires as in Victorian London. Those conditions hardly exist anymore anywhere in the world. The modern versions are ‘normal smog’ on the surface that is caused by roadtraffic and industry, and aviation smog on the level of the tropopause that is caused by airtraffic.
It seems that the emotional impact of the term ‘aviation smog’ is strong, which makes it effective to keep on using it.

Robert van Waning wrote:
Please have a look at the graphic animation that was published by the Dutch meteorologist Kees Floor:

Robert van Waning wrote:
[Hama Neggs had written: [The term ‘aviation smog’] is effective for someone who is trying to misrepresent reality.]
Come on. What other reality is there than airplanes dumping of ever bigger amounts of water vapour, soot and microscopic particles in the higher levels of our troposphere by airtraffic, causing unnatural cirrus clouds that have a similarity with smog?

Trailspotter wrote:
Yes, I do know that cumulonimbus clouds can grow taller than the airliners’ cruising altitudes, but it is not the point. They grow from the bottom, not the top. The satellite images of the day show that those huge hailstones resulted from a naturally formed thunderstorm and are not likely to have been caused by the air traffic, which is negligible in that area. In fact, if a thunderstorm cloud of this size is formed on a regular traffic route, the planes normally would not fly through it but take a lengthy diversion.

Spectrar Ghost wrote:
[Robert van Waning had written: .., causing unnatural cirrus clouds that have a similarity with smog?]
They have zero similarity.]
Smog is a combination of the words smoke and fog, because it is smoke that clings to the ground like fog. It’s primary component is ozone, with soot, sulfides, and carbonates usually present as well.
Cirrus aviaticus (contrails) are identical in all respects except source to natural cirrus clouds. They are ice crystals. The nuclei make up a negligible portion of the cloud.
There is no way cirrus can affect hailstone development. At -40deg where cirrus form, the saturation point is 0.1 g/kg of water. At 20C (68F) which is a good dewpoint for thunderstorm development, saturation occurs at ~15 g/kg. this means that the updraft air initially contains 150 times as much moisture as any upper level air entrained into the storm.

Robert van Waning wrote:
[Spectrar Ghost had written: Smog is a combination of the words smoke and fog, because it is smoke that clings to the ground like fog. It’s primary component is ozone, with soot, sulfides, and carbonates usually present as well.]
None of those conditions and prerequisitions is mentioned in the regular defintions of ‘smog’. You just make them up for your purposes, whatever they may be.
Cirrus aviaticus (contrails) are identical in all respects except source to natural cirrus clouds. They are ice crystals. The nuclei make up a negligible portion of the cloud.
Contrails originate from the condensation of water vapour on particles, both coming from the engines of airplanes. This origin is not at all identical to the origin of natural cirrus clouds.
The upper parts of most hailstorms consist of cirrus, of which at least a part is aviation smog.
My theory is, that when any hailstone is sent upward several times for unknown periods through an environment that is saturated with ice, it grows inexorably by the ice-crystals or drops of deepfrozen water that attach themselves to its surface.

Spectrar Ghost wrote:
Content from external source:
Smog is a type of air pollutant. The word “smog” was coined in the early 20th century as a portmanteau of the words smoke and fog to refer to smoky fog.[1] The word was then intended to refer to what was sometimes known as pea soup fog, a familiar and serious problem in London from the 19th century to the mid 20th century. This kind of smog is caused by the burning of large amounts of coal within a city; this smog contains sootparticulates from smoke, sulphur dioxide and other components.

Trailblazer wrote:
Sorry but your hailstone theory is complete bunk. If hailstones are ever present at contrail altitude it is because they are inside a thunderhead which has risen to that altitude. And a thundercloud contains vastly, hugely more water than any contrail cirrus, “aviation smog”, call it what you want. Hail forms INSIDE clouds which are already laden with water from lower altitudes. The minuscule amount of water in the upper atmosphere around them is totally irrelevant.

Efftup wrote:
[Robert van Waning had written: It seems that the emotional impact of the term ‘aviation smog’ is strong, which makes it effective to keep on using it.]
Even if it is completely accurate and misleading?
I am going to be blunt. No there is nothing wrong with voicing concerns.
However, Your website is deliberately misleading and scaremongering.
You KNOW the way most people don;t understand the science properly so the use on your main page of adding in the words DUMP, AEROSOLS and CHEMICAL SUBSTANCES along with YOUR DEFINITON of smog (without a proper explanation) is deliberately meant to create an emotional response and create concern that was not there before.
All the chemical substances in the planes’ exhaust, WHICH INCLUDE CO2 and Water, are there in the atmosphere whether or not a persistent contrail exists, and you don’t see any kind of “smog” when there is no persistent contrail.
Practically all your posts on this thread have been couched in terms like “I guess” and I would think” and yet those words don’t appear anywhere on your website, and certainly not on the main page. It is set up to make it look like you have all the answers and this is totally disingenuous.
If your website simply showed all these lines in the sky as examples of just how much aviation traffic there was these days, and then voiced your concerns over the pollution, I would’t have a problem with it but I understand you want page hits. Sadly it is the way of the world now that even the more reputable news agencies are now resorting to pathetic clickbait and misleading headlines to get you to read their articles.
A random passer by, looking for information on “chemtrails” stumbling on your website is most likely to skim and not click too many links so what they will take away from your site is that planes are DUMPING AEROSOLS and CHEMICAL SUBSTANCES in the air and this is a danger. They won’t see that YOU and your website are actually disagreeing with the “chemtrail” meme and don’t appear to think any deliberate “spraying” is going on.
YOU will be touted as proof of the bunk that other people are spreading.
If you don’t want this, and want people to concentrate on actual pollution, I suggest a subtle rewording of your main page.

Robert van Waning wrote:
The question is whether an environment that is saturated for ice (like aviation smog) can help to make hailstones bigger? I think it can.

Robert van Waning wrote:
Aviation smog is caused by burning large amounts of fossile fuel (liquid coal) in an environment that is saturated for (frozen) water vapour.
The heads of thunderstorms are saturated for ice. Aviation smog just ads even more ice particles to them, with predictable results.
Weather is about margins: Will there be clouds or not? Will it rain, freeze, be foggy, etc., or not? Aviation smog often helps to tip balances between cloudless and cloudy, thin and thick cirrus, dry weather or rain, rain or hail, etc.
Aviation smog can make a cloudless with a clear deepblue sky turn into a day with either a thin deck of cirrus clouds whch can eventually – with the help of natural cirrus – get thicker and thicker. The microscopic droplets of the aviation smog and natural cirrus coagulate constantly and keep on growing until they get too heavy and fall down. I think these originally tiny droplets eventually could become icedrops and eventually hailstones. This is a theory. Don’t shout at me but tell me please why this cannot possibly happen.

It is my intention to create greater awareness and serious concern. People think too little about the many undesirable consequences of too much flying.
Not all the substances in the exhaust of airplanes are as innocuous as you suggest. Leaving chemical waste behind is called dumping. Water vapour is an underestimated greenhouse gas.
Weather is about margins and tipping delicate balances. The pollution is permanent; aviation smog makes it visible.
What I try to achieve is that people become aware of some of the consequences of all that careless daily worldwide burning of enormous amounts of fossile fuel in the higher regions of our atmosphere.
I did not take thousands of pictures of aviation smog (that’s what it is; let’s call a spade a spade) over the past 20 years for my personal album. I have a ‘message to the world’ but I am certainly not misleading people.
I am more concerned about the reactions that I got here than by what crackpots might do with my pictures, solid information and honest opinion.

The upper part of a thunderstorm lays in an area that nowadays is more saturated for ice than it was before airtraffic became massive and influential on meteorological processes. It is my guess that this development strengthens convective precipitation in thunderstorms and tropical storms (that actually collect saturated air from their environment, thus adding to their mass and power). The process of condensation of (frozen) water on particles in the upper ‘smoggy” regions maybe strengthens the upward movement.

Robert van Waning wrote:
[Trailspotter had written: Well, l am not going to comment on the thousands of pictures on your website, but I’ll make a comment on a picture that you posted in the beginning of this thread (#33):
It may look dramatic like a smog blocking the Sun, but in fact it is just a natural cirrus photographed against the Sun.]


But how ‘natural’ is that cirrus? Would it have been there and/or would it have been so thick whithout the permanent exhaust of fumes and water vapour by airtraffic? Aviation smog does not stay in one place, but travels at high speeds at high altitudes around the world, attributing to the occurrence of cirrus where it would not have been without aviation.
Thousands of airplanes weave a permanent ‘ice curtain’ around the world, glass curtain of icedrops and -crystals. That cannot remain without consequences. That is what I am trying to draw people’s attention to, just to make them aware and let them start thinking about it. In the past twenty years no expert has convinced me that I should stop with this.

Spectrar Ghost wrote on Jul 15, 2015 #99:
I think it’s important to note at this juncture that Robert has some legitimate concerns. Aircraft exhaust pollution is growing along with air travel. Increased cirrus cover in the form of contrails increases surface temperature on an already heating world. The aesthetic concerns, while subjective, are also perfectly legitimate.
However, for these legitimate concerns to be taken seriously, they need to be separated from the idea of “aviation smog”. Aircraft pollute whether they have a contrail or not. Contrails are not a cause of steadily increasing cloud cover (in the sense of steadily increasing, thickening, and lowering skies) but rather a forerunner, a forecast tool. We won’t rehash the hail.

Robert van Waning wrote on Juli 15, 2015 #100:
[SR1419 had written: That is your website? That was one of the first website I used for debunking “chemtrails” as it had links to pics of contrails from throughout history/movies etc… This was like 10yrs ago. Seems like you removed all the old stuff. ]
After 20 years most of the links pointing to scientific reports were dead. I have neglected my website for a long time. The page was not updated since August 2005. Maintaining it was a lot of work that seemed quite useless and utterly thankless. Over the past 20 years I received very little reactions. I have continued taking pictures, though, and in the past weeks I have rejuvenated the pages with pictures of the last 5 years with new software.
As to historic pictures and movies, I think you mean the website of the Danish astronomer Holger Pedersen with whom I had regular contact in the first years of my anti contrail ‘crusade’. Pedersen was triggered by the fact that aviation smog (I prefer not to euphemize this result of pollution) hindered astronomers in their work. He was convinced that looking at the stars etc. with conventional telescopes would become impossible because of the permanent cover of high clouds made by airtraffic. I wonder whether he is still active as an anti contrail campaigner.
I really had expected a different reception on this website. Here I may call contrails ‘pollution’ but not ‘smog’ ( which it is) and leaving behind the stuff that comes out of jet engines after their daily burning of massive quantities of liquid cole in the higher regions of our atmosphere may not be called ‘dumping’ (which it is). According a senior member of this website aviation smog is merely a ‘forecast tool’. I am speechless. This website is not about debunking chemtrails but about defusing contrails (aviation smog) by aviation enthusiasts.

Robert van Waning, Jul 15, 2015 #102
Spectrar Ghost said:
Contrails are not a cause of steadily increasing cloud cover (in the sense of steadily increasing, thickening, and lowering skies) .. .
How do you know? Just look at the pictures. Or rather: look at the sky:


Spectrar Ghost, Jul 15, 2015 #104
[Content from external source:
Cirrus clouds alone are generally associated with fair weather. However, if they are followed by a sequence of lower and thicker clouds, they are often the forerunner of rain or snow such as in an approaching warm front. When only Cirrus clouds are visible, there will usually be a period of fair weather of 12 to 24 hours. It usually takes that long for the rest of the lower-level weather to catch up.

“Cirrus Clouds can foretell the arrival of a Warm Front associated with Low Pressure systems: they are the first, telltale signs.
An approaching warm front has a distinct sequence of clouds.
1. Appearance of Cirrus cloud in a clear sky, or a sky with fair weather Cumulus clouds.
2. Appearance of ring or halo around the sun indicating a layer of cirrostratus cloud.
3. “Thickening” of Cirrus into denser cirrostratus or Cirrocumulus clouds.
4. Appearance of lower clouds– altostratus, then stratus.
5. Altostratus becoming nimbostratus and start of rain. Rain is steady and light.
6. Continuation of rain until the arrival of the actual Warm Front. This sequence will take 12- 24 hours from the first appearance of Cirrus clouds but ultimately it is dependant on how the front is moving relative to your own position. If the front is moving parallel to your position, it may never get to you. The beginning of the rain marks the approximate halfway point between the appearance or the Cirrus clouds and the arrival of the Warm Front. The barometer will steadily drop throughout this process. As the Warm Front approaches, the wind will veer suddenly and the wind may become gusty. After the Front passes, the wind speed and direction should remain constant.”

I have a book (Eric Sloane’s Almanac and Weather Forecaster (1955)) that specifically references this type of visual forecast as well.

Robert van Waning, wrote on Jul 15, 2015 #105 :
Could it be that has to do with the funnel-shape of depressions? Whenever a weatherforecast predicts ‘veil clouds (sluierbewolking’) coming in from the Northsea’, I make sure that I have my camera at hand because those words mean that aviation smog is going to spoil the blue sky. Most of the time a (in this region regular) depression is passing from the Atlantic over Scotland and the northern part of the Northsea towards Norway. What we then see, looking upward, is the upper fringe of the depression passing over Holland. (The areas in Belgium and Germany where most of the heaviest hailstorms occur, seem to follow the lines of the isobars on the weathermap.)


Spectrar Ghost wrote: #106
No. Low pressure systems aren’t funnel shaped. However warm fronts do have a gradual incline as seen above. Cold fronts have a steeper front edge. These fronts are typically laid out something like this as a cyclone/low pressure system is at its strongest.

Direction of strom movement

Low pressure system #106

Contrails will form here

Robert van Waning, Jul 15, 2015 #108 wrote:
Exactly: funnel-shaped. Much wider at the top than on ground level.

Robert van Waning, Jul 15, 2015 #107 wrote:
Look at how contrails grow into cirrus ( that is not natural):

Metabunk #107

metabunk #107-2

Robert van Waning, Jul 15, 2015 #112
How do you know that cirrus is completely ‘natural’ and does not (at least partially) consist of icedroplets cq -crystals that originated by the condensation of (frozen) water vapour and aerosols, both coming from the exhaustst of jetplanes?
I mainly take pictures of contrails turning into cirrus that – after a while – can hardly be distinquished from natural cirrus. You can imagine what these contrails (the old and the new ones together) will look like, after a couple of hours or so:

metabunk #112
(Picture by Dutch meteorologist Kees Floor.)

By observing them and by following their transformation from thin lines into wide cirrus clouds:


Robert van Waning wrote #121:
After the visible smog evaporates (at least becomes unvisible for us) the microscopic solid particle that had acted as condensation after leaving the jet’s enigine, can serve the same purpose later on, several times even.
Robert van Waning wrote #123:

No, we do not agree. Lows do not cover the same amount of square miles on the surface as higher up. They are not straight boxes moving around.
Contrails are not just helpful forecast tools. They are a result of serious pollution in the upper layers of our atmosphere and I think their effects on weather, climate and the sun’s radiation are undesirable, to put it mildly.

Trailblazer wrote #125:
But, as repeatedly stated, the cloud would likely have formed anyway. Ice-supersaturated regions of the atmosphere are just waiting to form cirrus. The water is already there. If a passing plane didn’t trigger the clouds to form, then they would quite likely go on to form anyway. You seem to have the idea that the water in contrail clouds is “new” water that has been put there by planes. It isn’t, other than the tiny fraction that first initiates the phase change. Contrails do increase cloud cover, but the effect is not huge. Certainly, blaming contrails for a change from blue sky to grey cirrus cover is silly, because in such cases the amount of water vapour surely indicated that cirrus cover was approaching anyway.
Robert van Waning wrote #129:
Of course the cirrus aviaticus would NOT have formed later on without the presence of the exhaust fumes of airplanes. The aircraft supplied the necessary water vapour and condensation nuclei to tip the balance.
The water vapour plus aerosols from the jet engines work as a katalysator in the process of originating cirrus. After the initial aviation cirrus has ‘disappeared’ (become invisible, at least) the same particles can later on at a different place again help cirrus to form.
[Trailblazer had written: “Contrails do increase cloud cover, but the effect is not huge.”]
Look again:
[Trailblazer had written: Certainly, blaming contrails for a change from blue sky to grey cirrus cover is silly,]
Trailspotter wrote #130:
There are many microscopic solid particles of different origins in atmosphere that can serve as ice nuclei in natural cirrus formation: volcano ash, desert dust, sea salt, even some bacteria that evolved ice-nucleation as means of dispersal, etc. They do not stay permanently at high altitudes and eventually fall on the ground but they are replenished by natural processes. And it is not just the soot particles in the exhaust that initiate condensation; the main source of ice-nuclei is water vapour itself in the exhaust. Normally, it reaches the water-saturation level upon mixing with the ambient cool air and spontaneously condenses into water droplets that instantly freeze and become the nuclei. As the ice crystals grow, they break creating secondary nuclei, allowing the contrail spreading out.
Robert van Waning wrote #131:
The contrails can only grow into wide cirrus-like clouds because the airpressure was lowered by the approacing depression that (seemingly) is still far away. It is only far away on a weatherchart that shows the position of the low on the surface.
[Spectrar Ghost had written: It would have formed anyway, but slightly later.]
Or not. You don’t know without observing. And that is what I do before making pictures.
Trailspotter wrote #135:
Have you ever followed the evolution of the same contrail for a couple of hours? I doubt this very much. In that time the contrail will be blown out of sight by a high altitude wind, the typical speed of which is about 100 km/h. You can chase it by car on the ground, but I am not aware of anybody who would be doing this on a regular basis. Scientists usually follow the contrail evolution from above by using satellite images taken at some time intervals.
I’ve investigated many claims of contrail (“chemtrail”) grids spreading out to cover the sky with what you call “aviation smog” by looking at a “bigger picture” provided by the satellite images. In all cases, there was a cirrus layer coming into the area with substantial air traffic. As the layer approached, the initial contrails formed in the clear sky in the front of this layer, were replaced by new contrails formed within this layer. And the approaching cirrus was denser in the middle than near the edge, so from the ground it appeared that it gradually grew thicker. But the fact is, the incoming cirrus cloud would give the sky the same appearance even if there were no air traffic in the area at all.
PS And you seem to be aware of this, as the following passage of yours suggests:

Pete Tarr wrote #136:
Then wouldn’t you be better equipped to make your case that all that cirrus is created by spreading contrails rather than being an indicator ahead of a natural cirrus front, if instead of static pictures you use time lapses? The cirrus that forms from contrails is different to the cirrus layer that comes in later and is usually visually distinct from it; a time-lapse would show this much better than a singular frozen moment in time.
Robert van Waning wrote: #137:
I did not write that – after a couple of hours – these contrails would remain visible from the same spot. I only asked what they would look like, wherever they were after a few hours.
Aviation smog that is visible over a certain area is most probably caused by airtraffic elsewhere in the direction where the high winds come from. [Why couldn’t] that first, second or umptieth layer of spread-out contrails therefore not be called ‘aviation smog’?
Balace wrote #140:
As has already been pointed out by others, the contrails are literally a drop in the ocean in comparison to natural aerosols and other man-made interferences. The only reason I can see might be cause for concern is the fact that air traffic pollution is delivered at cloud-forming altitudes and therefore (under favourable conditions) is instantly visible, whereas most other pollutants are not.
But again, I would suggest that in comparison to all causes of aerosols/pollutants, it is miniscule isn’t it?
Robert van Waning wrote #141:
I don’t think so.
Trailspotter wrote #142:
As has already been pointed out by others, the contrails are literally a drop in the ocean in comparison to natural aerosols and other man-made interferences. The only reason I can see might be cause for concern is the fact that air traffic pollution is delivered at cloud-forming altitudes and therefore (under favourable conditions) is instantly visible, whereas most other pollutants are not. But again, I would suggest that in comparison to all causes of aerosols/pollutants, it is miniscule isn’t it?
You can see an even bigger picture on the NASA Worldview and check the cloud coverage upwind and downwind on the previous and following days.
PS Surely, the blue Dutch morning sky was spoiled later in the day:
Trailspotter wrote #148:
What you call ‘aviation smog’ is merely a natural cirrus with a few contrails embedded into it. If there were no contrails, it would still be the same cirrus cloud formed by natural processes involving vast volumes of atmosphere and huge amounts of water vapour in them.
Robert van Waning wrote # 150:
OK, you may call it like you want, just as am doing. I call this ‘aviation smog’, with or without anybody’s permission, and I think I have a good reason for that.
Robert van Waning wrote #152
[Trailspotter had written: What you call ‘aviation smog’ is merely a natural cirrus with a few contrails embedded into it.]
The same applies to the original ‘smog’: fog with smoke embedded in it, which makes it worse by the further condensation on the soot particles.
Don’t just look at the thin lines of the fresh contrails, but at the murky foggish stuff between them. How natural is that cirrus and would it have been there if there had been no airtraffic (somewhere else, upwind).


Trailspotter wrote:
Yes, it was a good contrail day in Holland and over the North Sea
on April 5, 2007, as can be seen from the ground photos:
Still, the area covered by the contrails is much smaller than the area covered by natural cirrus coming from the South. Just as I pointed above, the long persistent contrails are formed in the front of the incoming natural cirrus.
Robert bvan Waning wrote #157:
[Trailspotter had written: You are not the only person who take pictures of clouds and contrails.]
I know, and I hope more people will do it and publish the pictures, preferably with sequences and films. It is good that people get more aware of the effects and consequences of too cheap )and so too much) flying.
I still do not understand that almost everybody seems to agree that contrails are a symptom of pollution, but that most of you are against the use of the term ‘aviation smog’. Let’s call a spade a spade and stop euphemizing, ignoring and even denying what is going on in the higher regions of our troposphere.
‘Tropos’ is derived from the Greek verb for living. Pollution of air is not only bad when it occurs on the surface.
Deirdre wrote #159:
It’s not smog, it’s air pollution. it’s air pollution even when the cirrus cloud (ie contrail) doesnt form! the pollution is still there, your smog term sounds like you are dismissing that fact.
And contrails don’t always need the soot from the engines to form. (not a big deal, just don’t want you to think i agree completely with that part of your sentence).
Did you ever read through ?
I’m with Pete. If you arent going to make any attempt to show any real data- or convince us with anything other than guesses, bad science and trying to provoke emotional responses of fear -,  I’m a bit confused what the point of this conversation is. Such tactics aren’t going to work on this particular website, you are going to get frustrated because you are basically talking to a bunch of nerds who are pretty serious about science.
Robert van Waning wrote #160:
If we switched to hydrogen fuel with pure water exhaust (which will never happen*), water vapour would not condensate on aerosols and I wonder whether the contrails would grow as wide as they now do most of the times. The ice-drops cq -crystals that make up ‘conventional contrails’ seem to be hygroscopic. Do you know more about that?*) The present scale of aviation will come to an end when fossile fuels really become scarce and so too expensive. Intensive flying consumes the fossile resources that future generation would have used more wisely.
Deirdre wrote # 163:
(Content from external source:)
Exhaust particles alone will not create a contrail.
Contrails form when excess water on the exhaust condenses on cloud condensation nuclei. This liquid water then freezes and it is thisfrozen waterthat creates the ice-nuclei for the contrail to form from.
If you just had exhaust particles sprayed into ice-supersaturated air, you would not get much of a contrail (if any).
And if you has just high humidity hot air (say, from a hydrogen engine) sprayed into cold air, you WOULD get a contrail, as there’s lots of natural cloud condensation nuclei.
RvW wrote #166:
The key word is ‘spontaneously’.
After the ice has evaporated again from its nucleaus in a contrail, the same sootparticle can induce nucleation of ice again and again, as long as it remains up there. That is essentially different from spontaneous nucleation.
RvW wrote “167:
The contrails are almost everywhere, all the time, even when they no longer have the shape of thin stripes and so are no longer recognizable as ‘contrails’ but have become the vague haze that spoils an originally deepblue sky. The reason is that pollution by aviation is now virtually everywhere.

RvW wrote #175:


The ‘dense and persistent condensation trail’ that was left by the hydrogen fuel, is – by defintion – not a contrail nor smog, as they contain no particles that – after evaporation – can act again and again as condensation nuclei as long as the stay up there.
It is their almost permanent presence which makes that ‘aviation smog’ has become a permanent occurrence, although it no longer looks like the thin stripes of the original contrails. I call it ‘secondary contrails’ for lack of a better word.

RvW wrote #182:
According to NASA’s definition, contrails require ‘particles (aerosols) that exist in aircraft exhaust’.
Deirdre wrote #187:
“Solid particles” ARE necessary for condensation. and if soot is present (from engines) of course the vapor will condense on them as well as the ‘dirt’ or ice already in the atmosphere.
But you are correct that NASAs oversimplification would seem to be saying ‘there has to be soot’.
Think of it this way… ice is a solid particle. so once the vapor from the plane condenses (we’ll say on the soot), now we have an ice crystal and a thin contrail line. As i’m sure you have observed, once that initial line has been laid, overtime the line will often appear to GROW (not just spread out but GROW thicker and spread). the reason for this is there is water vapor in the atmosphere. the water vapor in the atmosphere condenses on the ice crystals of the original contrail causing it to GROW.
I’m over simplifying of course, but trying to show that water vapor does not need soot specifically to condense. Think of your tea kettle. water vapor comes out of the spout and then condenses into ‘steam’ without any soot being present.
RvW wrote #205:
Aviation smog is the result of aircraft pollution by airplanes that does not get the attention that it deserves in view of the probable effects and consequences on weather, climate and the quality and quantity of the sun’s radiation tht reaches the surface of earth.
I am forbidden here to call the daily worldwide leaving behind of vast amounts of combustion products in a sensitive part of our troposhere that is essential for our weather, climate and radiation ‘dumping’.
I may not even use the term ‘smog’ for the clouds and skywide haze that are caused by the emissions of the ever more intensive airtraffic at 10 – 13 kilometers high.
I quickly started to wonder on what kind of website I had landed. Are you aviation enthusiasts and lobbyists, being sensitive about negative connotations of your hobby?
Mick West wrote #214:
Contrails can form on particles that already exist in the air. Either in the air that is burnt, or the cold air it then mixes with.
Hydrogen burning engines make no particles, but leave contrails.
RvW wrote #216:
That depends on the definition that you use. My opinions are based on the NASA-definition, in which the presence of solid small particles is an essential element for the proper use of the term ‘contrail’ for this kind of vapour trail. Because of all the misconceptions, I will paste the full text here. I have stressed some parts of the text with * and bold letters.


RvW wrote #217:
This picture was made yesterday. It shows quite young, older and still older contrails. The oldest don’t look like contrails anymore, but like natural cirrus. It isn’t, though. Without the pollution by aviation, that part of the sky would have been cloudless and deepblue. Because contrails are the result of pollution, I prefer the term ‘aviation smog’.

Spectrar Ghost wrote #218

RvW wrote #219
I prefer the NASA-definition, as it has a historic origin. The term ‘contrails’ was originally used for the smog that becomes visible when water vapor condenses and freezes around small particles (aerosols) that exist in aircraft exhaust. Later definitions try to diminish the important part that pollution by aviation plays.

RvW wrote #221:
[Pete Tar said: What percentage do you believe is made up of what you define as pollution particles, versus water?]
What percentage of what? I do not understand your question, but even if I did, I wouldn’t know the answer. Firstly, I am not a scientist or expert, and, secondly, too little research into aviation smog has been done, for various reasons.
In contrails the pollution part act merely as condensation nuclei, but their size and weight don’t change while the condensated ice keeps growing. Not only particles out of the exhaust act as condensation nuclei, and not only water out of the exhaust freezes on the particles, and.
When I see those thin contrails grow out of proportion, I do not even know why that happens. The only thing I know is that the original contrails (with pollution particles as condensation nuclei) act as some sort of trigger or kathalysator.
I had hoped to find answers here, not the kind of unfriendly, derogatory, disparaging and even downright rotten reactions that I received.
For many reasons, aviation smog as a result of pollution by airtraffic is a serious matter and it deserves to be treated as such.

You’re being over-sensitive if that’s your impression – you’ve been challenged on your assertions and had them compared to the known facts on the subject, and had your seeming preference for your opinion over science challenged.
Perhaps you’d like to re-state the questions you don’t feel were answered?

RvW wrote #224:
I do understand the science enough to reject your answers, because you do not give the impression that you understand the science enough to come up with convincing answers.
You wrote, for instance: “What you see is not pollution, it’s water ice. The pollution exists, but you can not see it.” this would mean that water vapour does not condensate on the particles (aerosols) that exist in aircraft exhaust. This seems too improbable to mee to accept.
I came here because this website came up when I searched for ‘aviation smog’.
We disagree about the meaning of the word ‘smog’. My conception is based on definitions that do not mention a minimum percentage of solid particles that were produced by burning (liquid) coal in the fog that resulted from their combination with water vapour.
We also disagree about the meaning of the word ‘contrail’. My conception is based on the historic definition that was given by scientist of NASA who apparently do know what they are talking about.
I don’t think my conceptions are misconceptions and I doubt whether you are a scientist in the field of meteorology, specialized in what happens in the higher regions of our troposphere
RvW wrote #225:
Content from external source
Full Definition of SMOG
a fog made heavier and darker by smoke and chemical fumes; also: a photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen especially from automobile exhaust.
Content from external source
Fog or hazeintensified by smoke or otheratmosphericpollutants:exhaust emissions are mainly responsible for the smog.
I do not know defintions of ‘smog’ that mention a minimum percentage of smoke, soot or solid particles that ere produced by burning hydrocarbons like (liquid) coal.

My original questions were:
– What makes contrails grow so disproportionally?
– Do the solid particles in the exhaust of the airplane still play a part in that process?
– Why do meteorologists ignore, deny or euphemize contrails (aviation smog), whilst it is improbable that this development in the higher regions of our troposphere will not have effects and consequences that might be undesirable?
The question that arose during this discussion is: who of you are real scientists in this particular field? (Deirdre wrote that you all take science seriously, but she did not want to be called a serious scientist. Confusing.)

 Pete Tar wrote #231:

Some questions may be answered if you read some of the research done on contrails, here are a few links.

As to why meteorologists aren’t concerned in the way you are, because there simply aren’t the issues you think there are and they are informed on the subject. Have you tried asking any?

The question that arose during this discussion is: who of you are real scientists in this particular field? (Deirdre wrote that you all take science seriously, but she did not want to be called a serious scientist. Confusing.)

I don’t think anyone is an active scientist in the field, they’ve just done a lot of reading *of the science* due to personal interest and/or interest in combatting chemtrail misinformation.
Taking the science seriously means to respect and defer to the science, and to concede that the people who know what they’re talking about are most likely to be correct; you don’t have to be a scientist to do that.

RvW wrote #232:
Was it not the Greek philosopher Socrates who said: “The only thing I know, is that know nothing.”?
Contrary to most of you I do admit that I am not a scientist or even an expert in this field (neither is one of you). This doesn’t mean to say that I’m stupid or so. I am intelligent and highly educated enough (also in physics and meteorology, at the Royal Naval Academy and Economics at the Leiden University) to understand what I am talking about. I have studied this material and I also have observed and photographed contrails and aviation smog much longer and probably more intensively than anyone of you all. Let that be clear.
I have taken pictures of contrails since 1995 and I have published my pictures and all that I know and think about aviation smog on the internet since about 2002 on my and
You may learn a lot (also about wat I do and don’t know and understand) by studying the pages on .
Mick West wrote #240:
You think it’s a serious problem. But pretty much nobody else does.
The popularity of your web site should at least serve are a rough indicator of public interest in the problem. However your site gets so little traffic that it does not even register on the main traffic measuring sites.
This means it’s not in the top 20 million sites in the world, and gets less than 100 unique visitors a month.These are not unexpected numbers for a random personal blog. But for something you feel to be a serious cause, something you’ve devoted a lot of “effort, time and cameras” to, something you have actively been seeking to fight to promote for 20 years, then doesn’t this perhaps indicate you’re barking up the wrong tree?
Deirdre wrote #241:
Noone on this thread, or anywhere on this website that i have ever seen, has ever implied pollution from planes is not an issue in regards to effects on the planet. You are in essence ‘arguing with the choir’. But posting pictures of persistent contrails with no usable data attached and spreading misinformation about the trails and pollution from planes is not helpful to the cause of aircraft pollution’s effect on the Earth.You say you’ve asked questions that have not been answered, but that is untrue. Your questions HAVE been answered and answered correctly. I think you have consistently demonstrated that you are, in fact, not seriously interested in the issue or in real science that can lead to real intervention and solutions. and because of that this thread should be closed.

RvW wrote #246:
[Cloudspotter said:
[RvW: “My original questions were: – What makes contrails grow so disproportionally?”]
You: They don’t
[RvW: “- Do the solid particles in the exhaust of the airplane still play a part in that process?]
You: What process? (see point 1)]

Either you are in denial or simply lying.

NB: I added bold letters and asterixes * to the text, in answer to your remarkable statements.

RvW wrote #247:
So you think you and your team of senior members, staff members, moderators, etc. have succesfully ‘debunked’ my concern about the effects and consequences of contrails and aviation smog on weather, climate and the quality and quantity of the sun’s radiation that reacher the surface of Earth.
Your final and definitive argument was the impopularity of my (neglected) I hope you will forgive me for not taking this ‘argument’ too seriously.
In the past 20 years I have grown accustomed to ignoring, denying and euphemizing contrails, their follow-up and their probable effects and consequences. Initially I had not expected to encounter these types of reactions on this forum, but I learned fast. I simply had called at the wrong address, attracted by its misleading title which I mistook for genuine concern.
I found your address when I searched the internet for places were the term ‘aviation smog’ was used. You had picked it up from my website. It is a miracle that you had found it at all, given its obscurity.
RvW wrote #249:
RvW wrote #253:
[Spectrar Ghost said:
I wish I’d known that earlier. It would have made for a more concise conversation. It’s pretty much the opposite of real science though. Taking photos for twenty years and sticking them online makes you a photographer, not a scientist.]
Exactly. I never said or even suggested that I am a scientist. Do you mean that somebody who takes pictures cannot think properly and possibly come to the right conclusions (still to be confirmed by science)?
RvW wrote #254:
The word contrails is more associated with the first stage of aviation smog, the innocuous thin lines in the blue sky that airlines and travel agencies love to use in their advertisements.
RvW wrote #255:
What exactly did you mean by saying that contrails don’t grow? Here is a nice little movie, made by someone who sees that they do: ‘Jet Contrails grow into man-made clouds’.
And what are your objections against calling this apparent growth a ‘process’. Apart from a typically physical process, there might be some chemistry involved too as all kinds of different materials interact.
Somebody told me that the condensation particles are hygroscopic. That would explain a lot about this whole process, wouldn’t it?
Spectrar Ghost wrote #256:
Aircraft pollution is a real problem. The effect of increased cirrus cover (partly in the form ofcirrus aviaticus – contrails) is real. However, the effects (as borne out by the science) are not what you claim, and the two should not be conflated with each other; they are independent.
Increased cirrus cover is from increased moisture in the upper atmosphere, from many sources. Aircraft pollution occurs independent of contrail formation, as you have concurred.
Your ‘aviation smog’ is an approaching warm front.
Efftup wrote #257:
So contrails are innocuous, being made entirely of ice crystals, so when they spread out (even hygroscopically adding MORE water from the air) they are still made of water. Just shows the Aviation Smog tag is totally inappropriate.
We have established that a lot of air traffic creates pollution (which is there regardless of whether or not a contrail appears so therefore a totally separate issue) and is a cause for concern.
We have established that extra cirrus cloud cover caused by aviation may contribute to global warming and is being studied.
On this I think we are ALL agreed.
Any other discussion of persistent contrails can really only be down to finding them unsightly.
RvW wrote #261:

It is their apparent innoccuousness that makes contrails so dangerous. It makes most people (also those without any interest) think there is nothing wrong with aviation cirrus and that there is no reason to be worried its omnipresence. ‘Indistinguishable’ for the naked eyes does not mean that those contrail derived clouds are similar to natural clouds.

RvW wrote #262:
Contrails are not only a result from pollution but they pose a problem by themselves too. It is not an issue that can be separated from its cause: severe pollution by too much airtraffic.
Apart from their probable contribution to global warming, the part contrails play in the weather system may not be underestimated either.
Spectrar Ghost wrote #264:
It didn’t say similar looking, it said indistinguishable. They can’t be told apart at all, even by sampling.
They’re clouds. The only difference is that while regular cirrus form when parcels are lifted until the temperature is below the dewpoint, contrails form when moisture is added until the dewpoint is above the temperature. This doesn’t change their physical characteristics in any way.

RvW wrote #267:

Who are you people? Valiant Defenders of the Oppressed Contrails? Members of the Contrails Conservation League?
Senior- and staff-members of this forum try to detach contrails from the pollution that causes them. That is not just remarkable but even suspect.
Without pollution by aircraft those clouds would not have been there. Contails are man made clouds. Talking about similarity with (or distinction from) natural cirrus, that means a hell of a difference.
Another difference is that the solid kernels of the ice droplets that make up contrails, remain after the droplets have evaporated and can function again and again as condensation nuclei for the formation new icedroplets and clouds as long as the remain up there in the tropopause. You could call those clouds ‘secondary contrails’ or ‘next generation contrails’.
Contrails do indeed grow in proportion to the amount of available water vapour in the air, but that amount is enlarged – together with that of solid particles (acting as condensation nuclei) – by intensive air traffic. That is why I asked to take the changing conditions in the tropopause into account. And their cause, of course.
You wrote that the condensation particles are made of ice. Why do you ignore the solid particles in the exhaust that acted as condensation nuclei? Those solid particles are of different substances that come free when fossile fuel is burnt.

RvW wrote #268:
Normally, ‘indistinguishable’ means that two things (or persons or whatever) cannot be told apart with the naked eye. But who am I to teach you your own language?
They’re clouds, alright, but not normal, regular, natural clouds. That is why they are not indicated by a normal name. Their physical characteristics differ because of their origin and their substance, because they contain as kernel a solid particle from the exhaust of an airplane that has acted as their condensation nucleus. See the definition by NASA.
Spectrar Ghost wrote #269:
US aviation uses ~3.6 million tons of jet fuel annually, if you remember. That’s. About 3.25 billion kilos.
.4% of combustion products are residual products that may serve as CCNs.
Therefore U.S. aviation produces ~1.306e7 kg of these byproducts annually, or .0006% of available CCNs globally. Even assuming US aviation is only 10% of worldwide aviation this is a very small proportion of available CCNs.
Since there are hundreds to thousands of these particles present per CC of air anyway, it’s not a significant factor in contrail spread or overall cirrus formation. As pollution it needs to be minimized anyway, but again, your conflation of contrails with aviation pollution is baseless.
Correction: 1 ton in is not one ton out. 1.24 T of water is 27.2% of combustion products. Thus my results need to be multiplied by ~5. Conclusions don’t change though.
RvW wrote #271:
We are discussing contrails here, and their original cause, however much you try to drag the attention away from that.
As we are talking about extremely small and light solid particles that float around in the tropopause, their numbers are more important than their weight. In the wake of the aircraft, the CCN’s coming out of the engine outnumber those that are already present in that environment. That is where the contrails are made. After that, the contrails grow and keep on growing out of proportion by a process in which the already present CCN’s play an ever bigger part.
Contrails are the result of airpollution. In this picture you can see three contrails with maybe 20 minutes between them. The vague clouds in the blue background are probably also caused by aviation: aviation smog.
The typical ‘flagging’ of a contrail:
The cirrus to the right of the spread-out contrail is undistiguishable from natural cirrus. Stiil, it would most probably not have been there without the pollution by one or more airplanes:
RvW wrote #273:
When we are discussing contrails, we are talking about the water vapour that – under the right conditions – condensates on the solid particles that come out of the same engines of an airplane. It’s a matter of definition.
Red may look like red, but there are so many shades that people could disagree about something being red or not. Only with the help of a spectroscope it is possible to define what is really red.
We disagree about the meaning of undistinguishable. It depends on the method you use to tell the difference (if any).
Two things that seem indistinguishable can be proven to be almost totally different, apart from their appearance.
What looks like natural cirrus might be aviation smog. In many cases it is. Just have a look at the pictures on my website. On many occasions it is only possible to say a certain cirrus is in fact aviation smog if you have followed the process of growing and dissolving of contrails (that are aviation smog themselves).
Trailblazer wrote #274:
ALL clouds, natural or unnatural, depend on a “kernel” of non-water material. That is what cloud condensation nuclei are. Are you seriously trying to suggest that “natural” clouds are 100% water? Totally and utterly wrong. Clouds nucleate on all sorts of things: mineral dust, soot, sulfate particles from volcanoes, even charged particles resulting from cosmic rays. Why single out aircraft?
RvW wrote #279:

I probably couldn’t. One of the boxes would not be filled with air that was not (recently) polluted by aircraft. Aviation adds to the (until recently relatively little) pollution of the sensitive troposphere.

Robert van Waning wrote #281:
I do not rule out any other source (old or new) of pollution. A contrail in the wake of an airplane contains air that is mainly polluted by that airplane.
CCN’s spewed out in the troposphere daily worldwide by airplanes are quite new, as you probably know (although I even start to doubt that). That means that the types of clouds in this photograph are fairly new as well:
Spectrar Ghost wrote # 282:
It sounds like you are saying that the way to tell a contrail from any other cloud is to watch them form. Is this true?
To convince me (or anyone elss) they are a threat you need to show that they are physically different and more dangerous as they persist; I.e. Independent of their formation. Show how any cloud with the characteristics of a contrail post-formation is inherently more dangerous than a natural one.
Cirrus aviaticus are fairly recent, being only 80 or so years old. Until you show how they differ from other cirrus it hardly matters though. “They come from airplanes” is a statement of source, but does not show differentiation.
RvW wrote #290:
Aviation cirrus originates from condensation on extra doses of condensation particles from the exhausts of airplanes in the troposphere where previously these solid particles were not present.
Also, please do not forget that contrails and aviation smog are new, extra clouds that would have not been there without the massive airtraffic of nowadays. Extra clouds means that there will be clouds where previously there weren’t and existing clouds will get bigger than before. Changes in a well-balanced system will not be without consequences and effects. What makes you so sure that those will be always desirable?
RvW wrote #291:
What planes are adding is a localised high concentration of water PLUS a localised high concentration of CCN (‘Cloud condensation nuclei (CCN), the aerosols that act as the initial sites for condensation of water vapor into cloud droplets or cloud ice particles. (source, with a nice example:
The condensation particles are not already there but constantly brought up by the burning of massive amounts of liquid coal in an environment that had been relatively clean.
Trailblazer wrote # 294:
The number of CCNs in the atmosphere attributable to aircraft is a minuscule fraction of the total.
Once again, I am spelling this out as simply as possible: aircraft create contrails because of the water they emit, not because of the CCNs they emit. (I am talking about engine contrails here, not aerodynamic contrails, which are also independent of pollution.)
If you could somehow capture all the water vapour produced by a jet engine, but leave all the soot, sulfates and other CCNs in the exhaust, it would not create a contrail. Do you understand why?
RvW wrote #295:
Saturization is probably what you mean. Still:

( )”
Emphasis added by me.

Trailspotter wrote #297:
This is not true. The exhausts of airplanes is a product of reaction between hydrocarbon fuel carried by the plane and oxygen from the atmosphere. It consumes 3 tonnes of oxygen per each tonne of fuel. The amount of air passing through the jet engine is at least 20 times more, about 60 tonnes of air per each tonne of fuel, which would have volume of 50,000 cubic meters at the standard pressure of 1013 hPa, or 200,000 cubic meters at the cruising altitudes of 250 hPa. At the typical concentrations of particulates in the air, 100 – 1000 particles per cubic centimetre, it gives 2•10^13 – 2•10^14 particles injected by the engine per each tonne of consumed fuel. For comparison, the amount of soot from the burning one tonne of jet fuel is about 20 grammes. If this amount is divided into 2•10^14 particles, one soot particle would weigh 10^-13 grammes and have volume of 5•10^-14 cubic centimetres = 5•10^-20 cubic metres, that is, its dimension would be less than one micrometer (10^-6 metres), which is a typical size for the suspended atmospheric particles.
These calculations show that the “extra doses of condensation particles” in the engine exhaust from the burning aviation fuel are comparable to or probably even less than the “doses of condensation particles” that were already present in the atmosphere and passed through the jet engine.
On a separate issue, the ice nucleation particles are required for the exhaust contrail formation but not for contrail spreading. The spreading occurs on the secondary condensation nuclei, which are derived from the ice crystals of the already formed contrail. Therefore the spread contrail does not contain a solid kernel in each ice crystals, the 99.9…% of its crystals are made of pure ice.
RvW wrote #316:

Fact is, that I also dislike the spoiling of a natural sky. In the first place I am worried about the probable effects and consequences of these ‘new clouds’. That is what I’ve always written and what should not be ignored or distorted by the Inquisition of the Contrail Conservation League.
Do you really see ‘plenty of natural cirrus’ in this photo? Where? What does it look like? How do you know?

RvW wrote # 323:
How can you tell whether cirrus is really ‘natural’ and so is not caused (partly) by (old or recent) exhaust fumes of airplanes?
I just went outside and took a couple of photos of cirrus. Can you tell which ones are caused by one or more airplanes and which ones are ‘natural’?
RvW wrote #325:
During the day, with the sun high in the sky, it is very hard to let contrails and aviation smog come out clearly enough. With the sun shining sideways, they become more visible. It has also to do with the cooling down of the atmosphere:
Efftup wrote #326:
I see you’ve started using the term Liquid coal now.
Seeing as how Kerosene has been pretty universally fractionally distilled from Petroleum as opposed to bituminous shale for about 150 YEARS, do you have ANY reasonable reason for using that term?
Your transparent attempts to make the pollution from planes sound much dirtier than they are is probably a very good reason you find that people don’t take you seriously.

RvW wrote #327:
Content from external source
Kerosene is an oil distillate commonly used as a fuel or solvent. It is a thin, clear liquid consisting of a mixture of hydrocarbons that boil between 302°F and 527°F (150°C and 275°C). While kerosene can be extracted from coal, oil shale, and wood, it is primarily derived from refined petroleum. Before electric lights became popular, kerosene was widely used in oil lamps and was one of the most important refinery products. Today kerosene is primarily used as a heating oil, as fuel in jet engines, and as a solvent for insecticidesprays.
Read more:

As opponent of the massive spillage, pollution and damaging the earthly climate system by too much flying, I have grown used to the many ways proponents of aviation try to make flying sound clean and innocuous.
People do not have to take me seriously if they don’t want to, as long as they look at my pictures with an open and rational mind.

RvW wrote #328:
After 20 years of taking pictures of contrails and their aftermath and meeting mainly a baffled miscomprehension, after this discussion and after yesterday’s weatherforecast (‘maybe only some cumulus’ (Dutch: stapelwolken)) and especially after this posse-like discussion, I get the message: Contrails do not exist, simply because they can be ignored, denied, argued away and lied about.
I will no longer try to win your understanding, but maybe you can tell me which of the following pictures (taken yesterday, the day with ‘only some cumulus’) show ‘natural cirrus’ (trailspotter) or ‘cumulus’ (the Roal Dutch Meteorological Institute KNMI):
RvW wrote #331:
The valiant Defenders of the Holy Contrail are missing what they try to ignore: The fact that any change in the composition of our troposphere cannot remain without effects and consequences, some of which might be undesirable.
Originally the sky was without aviation smog. Nowadays the sky is covered by it, daily, around the world, even if you do not want to acknowledge it for what it is, namely an effect of pollution by aviation which cannot possibly remain without effects of its own. That’s how complex systems work: partly predictable, partly counterintuitive and totally unpredictable.
The pictures were taken just now. I didn’t even have time to manipulate them (only joking):
Spectrar Ghost wrote # 332:
Not surprising, given the low traversing Britain right now. Upper level runoff from the convection most likely. Very unlikely to be the result of aviation.
Edit: actually it’s exactly the warm fropa (frontal passage) scenario explained earlier. See below.
SR1419 wrote #333:
Nobody is ignoring that planes emit pollution in their exhaust. Nobody is ignoring that planes sometimes induce cirrus cloud formation. Indeed, there are decades of research on just those very subjects.
So…again what is your point?[..]
I live in one of the most heavily air trafficked parts of the World and havent seen any contrail cirrus in weeks if not longer. The skies above me are clear blue for as far as the eye can see despite there being 100s if not 1000s of planes in the sky. If you want to be taken seriously, do not make things up.
MickWest (Administrator) wrote #336:
Same here, in Northern California. It’s the weather.
Spectrar Ghost wrote #334:
Note the occluded low over Britain with a warm front traversing the Netherlands. Since these are surface boundaries, it’s entirely likely you’ve seen contrails followed by increasing cloudiness over the last 12hr or so.
As was explained earlier, warm fronts are an excellent source of upper level moisture as the warmer moister surface air rides up the frontal discontinuity.
Trailspotter wrote #335:
One can watch the incoming front in a time lapse video from the webcam near the Hague pointing in western direction (a screen recording is attached). It begins with a blue sky in the morning and ends with cirrostratus at the sunset (note the sun dog in the screenshot below). There are occasional contrails too, but they are quickly blown away:
#335 Screen Shot 2015-08-03 at 21.13.51

RvW wrote #338

Really? And then? What happens with the exhust fumes, the water vapour and the condensation nuclei? Do they vanish into thin air? Or can they come back to haunt us under a different disguise?

Trailspotter wrote # 339:
As has repeatedly been said, the water vapour and condensation nuclei released by aircraft represent a tiny fraction of what is already up there. The water vapour just enters the water cycle. Yes there is pollution being emitted, just as there is from just about all human activity.
RvW wrote #340:
That is what you see, looking with your naked eyes, judging the unpolluted purity of layers of thin air at 10-13 kilometer up.
What happened to the exhaust fumes, the water vapour, the soot and the other CCN’s? Vanished? Completely gone forever? Magical, isn’t it?
Just like a conjurer’s trick. You see what you want to believe.
Spectrar Ghost wrote #343:
Given the fact that the synoptic environment would be conducive to exactly the same cloud cover in the absence of aviation, why do you feel it is relevant? Practical forecasting of approaching warm fronts by progressive thickening and lowering of clouds predates aviation.
You’re taking a microscale event (contrails) and attributing to it the effects of a synoptic scale event (an occluded low centered several hundred km distant). Weather just doesn’t work like that I’m afraid.
I’m glad you made the effort to show us images in near real time when relevant analysis products were still readily available. It confirmed my suspicions nicely.
It’s too bad you’ve apparently not availed yourself of them. They’re generally far more informative than simple cloud spotting. If I see an interesting cloud formation radar and satellite imagery are my go-to since they give a much better sense of the larger scale environment.
That said, I doubt you’ll have any inclination to change your beliefs and habits at this point, which is disappointing. Good luck.
Efftup wrote #342:
I think this article is interesting talking about impact of different modes of transport:

It discusses how the environmental impact of different transport also depends on the timescale you are looking at.
It is linked to THIS paper.:
The Guardian article states that air transport is worse overall over the short term because the non CO2 pollutants have more of a warming effect but those do dissipate quicker whereas cars are worse over the long term due to much more CO2 per passenger mile that contributes far more to an overall warming effect.
However, it then claims Ships actually negate the warming of BOTH in the short term because of the sulphate particulates in the exhaust (GEO ENGINEERING!!!!!) which do actually reflect some of the sunlight and cause a cooling effect, but again , like cars, over the long term this effect is clearly not quite so prominent.
All of this shows how pollution and global warming are much more complex than anyone likes to admit when they have a particular favourite culprit or saviour.

RvW wrote #345:
Pollution as our saviour. I’m sure this view is less inconvenient than mine and will produce applause in this pro-aviation environment.
My position is that hydrocarbons of any kind should not be burnt at the present scale in the sensitive higher regions of our troposphere, especially not because of the ephemeral purposes and the untaxed ways this generally happens.
RvW wrote # 346:

You nor anybody else can stop me calling kerosene ‘liquid coal’ to express how I think of burning hydrocarbons of any kind in the troposphere.

Efftup wrote #351:

What more do you think people SHOULD be doing that they aren’t?
Across the board, there people striving to find cleaner solutions to all industrial processes and transport needs, more efficient power stations, Electric cars, and even Electric planes.Obviously nothing is completely green, not even wind and solar, but people are working to make things better.
Until Electric passenger planes capable of crossing oceans are a reality, the only way to reduce the air pollution and cirrus aviaticus is to reduce the number of flights.
The only way to stop people wanting to fly is to improve communications to the point where people will not feel they need to. If I could communicate across the Atlantic to my girlfriend for free or a low cost Virtual Reality call and it would really feel like I was in the same room and as well as seeing and hearing her, it felt like I was actually holding her and smelling her scent as I did so, then I might be prepared to not spend over £1000 for a flight on a regular basis.
RvW wrote #352:
[Efftup said: [..]what more do you think people SHOULD be doing that they aren’t?]
Well, for starters, meteorologists and media should try to be more HONEST about all the negative sides, effects and consequences of massive flying. Also, flying flying should be taxed more heavily, because it is far too cheap in relation to the pollution, noise and damage it causes.
The only way to stop people wanting to fly, is too make it much more expensive, a luxury.
Talking about HONESTY and TRANSPARENCY, take – for instance – today. According to the weatherman of the Dutch public radio station Radio 1, there would only be some ‘sluierwolken’ (veil clouds). The CAUSE of this particular type of cirrus is NEVER MENTIONED!
Your Senior member Spectrar Ghost would probably say: “Very unlikely to be the result of aviation.”
 Spectrar Ghost wrote #360:
Here are the five points I’ve arguing, as simply as possible.
1) Aircraft pollution is non-trivial, but modest compared to most other forms of transportation, in absolute terms and particularly in pollution per passenger mile. As such it would be likely that extra taxation on air travel would increase the total pollution load instead of decreasing it.
2) Aircraft pollution is a problem whether contrails form or not.
3) Cirrus aviaticus have measurable effects on weather, independent of their pollution content. The two can safely be treated seperately.
4) Contrails do not and can not contribute significantly to CCN or water availability in non-aviation cirrus, based on aviation emissions as a proportion of total CCN or water input annually.
5) There is no plausible mechanism by which hailstone development would be affected by the presence of contrails.
I agree with you on the potential effects of aviation pollution and contrails. Your talking points and naming conventions are riddled with factual inaccuracies, however.
RvW wrote # 361:
I disagree on all points. Talking about factual inaccurancies you certainly take the cake.
Here is today’s harvest of non-trivial aviation smog (or ‘sluierwolken’ (veil clouds) as Duch meteorologistst prefer to call them):
#361 2015-08-06 07.54.24
 #361-2 2015-08-06 08.59.25
#361-3 2015-08-06 09.02.31
#361-4 2015-08-06 10.04.12
RvW wrote #362:
Yesterday there was an interesting mix of wispy (probably) natural clouds and contrails, old and new ones. You need to follow their shapes, development and behaviour and you also need some experience to tell them apart:
#362 2015-08-05 20.36.00
Spectrar Ghost wrote #365:
Avgas and jet fuel: ~200 million T/yr of CO2.
Gasoline and fuel oil (read diesel) ~1,500 T/yr.
Aviation: .24 kg/passenger mile (short flight), .18 kg/passenger mile (long flight)
Cars: .35 kg/passenger mile (new cars), .44 kg/passenger mile (all cars)
Busses: .3 kg/passenger mile (commuter), .08 kg/passenger mile (distance).
Rail: .17 kg/passenger mile (commuter), .19 kg per passenger mile (distance)These surprised me, being both flatter between types than I’d imagined and, in the case of long distance bus trips, much lower.However,…_transportation/2014/2_Moving_People/table2_3 :

Based on this, changing the taxation on air travel could in fact reduce CO2 load, provided the bus/rail ratio remained constant, passengers didn’t decide to shoulder the extra costs for convenience or just drive, and traffic was not impacted excessively.
I’d imagine the shorter (and more polluting) flights would be most affected. Interesting. Aviation pollution is a relatively modest proportion of the U.S. transportation sectors output (and a minimal proportion of total CO2 pollution, ~3%), but it seems encouraging long distance bus trips would be able to decrease the overall load somewhat.
On the other hand, I’ve tried to make clear that aviation pollution is important, but insignificant compared to the total pollutant load. Shaving off even a quarter of 3% is still just .75% difference.

2) Aircraft pollution is a problem whether contrails form or not.
You disagree here? Is there a doubt that aircraft exhaust is the same whether contrails occur or not?
3) Cirrus aviaticus have measurable effects on weather, independent of their pollution content. The two can safely be treated separately.
There are plenty of available CCNs, as has been shown. Your dependence on the definition on the NASA website to say that vapor trails that do not form on exhaust particles are not contrails despite both explicitly contradictory definitions and excerpts from papers on contrail physics is essentially a no true Scotsman fallacy.
4) Contrails do not and can not contribute significantly to CCN or water availability in non-aviation cirrus, based on aviation emissions as a proportion of total CCN or water input annually.
I truly don’t think I can make it more explicit than a previous post:

Your veil clouds probably have some aircraft exhaust pollutants in them, because that’s how diffusion works. The math shows it will be measured in ppm of the total CCNs (I can’t find a good source of US aviation as a percent of world, so I’ll let my first blush guess of 10% stand. That would mean 60ppm). They will all be substances that already exist in the atmosphere, so you won’t even know which ones they are.

5) There is no plausible mechanism by which hailstone development would be affected by the presence of contrails.
I spent several pages on this. It’s what got me in here in the first place. Reread that section of our conversation and point out where you think I’m wrong.

Efftup wrote #366:

Not as easy as it seems. You might not feel the need to fly anywhere but plenty of stuff is air freighted, and people often need to visit loved ones or go on business trips.
Even the holiday makers HAVE to fly if they are going to get to a far flung destination.
How are YOU going to persuade someone used to the wet and cold of North Yorkshire that they must spend their 2 week holiday in Skegness instead of Bali?
So yes, you will make flying a luxury so the price of goods and services increase dramatically and now only a very few will be able to go on holiday.
This doesn;t really work in the long run.
Just like those draconian measures aimed at pushing motorists out of their cars don’t
If I live in one place and work somewhere where there is NO bus or train service or not at the time of day I need to start work, and it;s too far to walk or cycle sensibly then I pretty much HAVE to drive. Increasing the taxes just pushes me closer to destitution.
Because of the distances involved, flying doesn’t really have a viable alternative.

Why not for free? I was talking about COMMUNICATIONS. I very rarely telephone my girlfriend cos it costs a LOT of money, but I can make a SKYPE call which has audio AND video for Free.
Much as we all have lofty ideals, we have to look at the way human beings think and behave. We can’t always control them all the way you would like to. You have to find incentives to make people change their behaviour for the better. Carrot is often way better than stick.

RvW wrote #367:
The term ‘aviation smog’ suits me fine. I even think it might become an accepted term fo the phenomenon.
Weather presenters of the media] should tell it like it is. They always mention the cause(s) of smog on groundlevel, so why not of smog higher up, at 10 – 13 km height?
For many reasons [flying] is simply not sustainable to let everybody fly as often and as far as they want. With taxation and quote this will have to be curbed, one way or the other. Too much flying is harmful, not only to the scarce resources, the environment and the climate, but also for people themselves and for the societies they live in.
In the long rum many things that are considered ‘normal’ at the moment, will come to an end. The present way of living is simply not sustainable. I’m sorry for your kids.
Consider moving to where you work or where your (future) wife lives.
[Efftup had written: Because of the distances involved, flying doesn’t really have a viable alternative.]
Yes: Don’t go. Don’t fly, anyway.
[Efftup had written: Why not for free? I was talking about COMMUNICATIONS.]
No, you are talking about spillage of scarce energy resources, about making a lot of noise, about pollution of the air both at ground as high in the troposphere and about destabilizing the climate.
[Efftup had written: Much as we all have lofty ideals, we have to look at the way human beings think and behave. We can’t always control them all the way you would like to. You have to find incentives to make people change their behaviour for the better. Carrot is often way better than stick.]
There is nothing lofty about being prudent, rational, sensible and aware of the consequences of what you still think is ‘normal’.

According to the Dutch weathermen, there would be some ‘sluierwolken’ (veil clouds, cirrus). In reality, the ONLY clouds during the WHOLE day were aviation cirrus:

#367-2 2015-08-06 13.59.52
#367-3 2015-08-06 18.10.14
#367-4 2015-08-06 20.58.02
#367-5 2015-08-06 21.20.51
RvW wrote #368:
I do not worry too much about CO2, because many other people do that already.
It is not so much the amount of pollution by aviation that worries me, but the location where aviation daily burns massive amounts ‘liquid coal’ all around the world, to wit in the sensitive higher regions of our troposphere.
[Aviation pollution[ is relevant because of the LEVEL at which the extra water vapour and the extra cloud condensation nuclei are dumped.
The contrails are the symptom which itself has negative effects, apart from pollution.
[Spectrar Ghost had written: There are plenty of available CCNs, as has been shown. Your dependence on the definition on the NASA website to say that vapor trails that do not form on exhaust particles are not contrails despite both explicitly contradictory definitions and excerpts from papers on contrail physics is essentially a no true Scotsman fallacy.]
I agree with NASA’s definition and I’ll stick to it until somebody convinces me that I shouldn’t. You didn’t.
[Spectrar Ghost had written: Your veil clouds probably have some aircraft exhaust pollutants in them, because that’s how diffusion works. The math shows it will be measured in ppm of the total CCNs (I can’t find a good source of US aviation as a percent of world, so I’ll let my first blush guess of 10% stand. That would mean 60ppm). They will all be substances that already exist in the atmosphere, so you won’t even know which ones they are.]
At that high level?

It still seems logical to me that more hailstones will originate at higher levels as a result of the exhaust of airplanes, and that they will also start growing at higher levels than before.

I have another theory, which will surely appall you: I think that ‘aviation smog’ (I love that word) will lead tot concentrations of air masses with higher densities at higher levels than before aviation. The result will be somewhat comparable with the ‘plastic soup’ in the oceans. This would lead to higher precipition in some areas and (thus) more drought in others, and also to more forceful tropical storms. It’s just a thought..

RvW wrote #370:
‘Random photos of aviation smog are my way of making people aware of the improbability that this development in the higher regions of our troposhere remains without any effects and consequences, some of which could possibly be undesirable.
Landru wrote #371:
Someone’s (your’s) attempt to add aviation smog to the Wikipedia article on smog was met with derision.
Spectrar Ghost wrote #372:
Derision may be a bit of a strong word. Besides, the section was removed in Jan 2007, so it’s not very relevant.

Deirdre wrote #373:
Contrails are like “pigs in a blanket“. the “pig” is the pollution that ALWAYS comes out of engines. ALWAYS, whether you see it in the sky or not… it ALWAYS comes out of the engines.
The “blanket” is WATER> Ice chrystals that cling onto the “pig”.
The “blanket” ie the Contrail.. HAS been scientifically studied as far as its affects on climate. IF you used the term “contrail” you could use those scientific studies to PROVE your point. Because you do have a point, and its been scientifically studied. here is one ex:

Posting pictures without scientific context (dates times) is useless. You dont need to get more people interested in your cause, because the governments are already interested and studying and planning re: your cause.

Robert van Waning wrote #374:
[Landru said: Someone’s (your’s) attempt to add aviation smog to the Wikipedia article on smog was met with derision.]
Anonimous derision, you mean, by people who do not have the courage to stand behind their own opinion (or lobbyism).
Anyhow, even you, as a would-be moderator of a would-be scientific forum, should know with how much derision new ideas, viewpoints and theories have been met that later have become fully accepted.
Basing myself on NASA’s definition of contrails, I think I can safely call contrails ‘aviation smog’, especially because it apparently hits a nerve.
I can’t really rememember ever having attempted to add aviation smog to Wikipedia. That must have been like almost 15 years ago, or so, in my activist years.
With aviation huge interests are involved. As David fighting Goliath I still hope that my pebble will hit a sensitive spot.
‘Nul n’est besoin d’espérer pour entreprendre, ni de réussir pour perseverer’, was the motto of William of Orange, ‘the father of our fatherland’.

Robert van Waning wrote #376
[Deirdre said: [..]The “blanket” ie the Contrail.. HAS been scientifically studied as far as its affects on climate.]
So I should rest my case, you mean? I won’t, because I do not think it gets enough attentin and research, and it is still not mentioned in the weatherforecasts as the real reason behind the cirrus that often clouds a sky that – without aviation – would have been cloudless, unpolluted and unspoilt.
I do not worry about global warming, because enough other people do. However, I do not hear enough about the probable effects of aviation smog on meteorological processes and on the quality and quantity of the sun’s radiation that reaches the surface of earth.
[Deirdre had written: THE “pig” ie. pollution from engines including planes. HAS also been studied. (and continues to be studied).]
Good! Never enough, though.
[Deirdre had written: Posting pictures without scientific context (dates times) is useless.]
So are your efforts to make me stop.
[Deirdre had wriiten: You dont need to get more people interested in your cause, because the governments are already interested and studying and planning re: your cause.]
Cute, naïve and undemocratic.

Robert van Waning wrote # 378:

Emphasis added by me.
Your ‘communications’ have a down side, just like aviation. It does no harm to become aware of that.

Robert van Waning replied to Deirdre #379:

Then don’t be concerned. Apparently you do not belong to my target group. ‘Be happy, don’t worry.’

 Landru (moderator) wrote #387:
You’ve made claims on this website. People have asked you to provide evidence supporting those claims. This is in keeping with the rules and reasons for this site. What is it are you trying to do?
Robert van Waning wrote #388:
What other claims did I make other than expressing my belief that it is improbable that a major change in the composition and build-up of our troposphere can be without effects and consequences? I use my photos to make clear what I mean. Nothing more. I reacted to the original question whether there are any anti-contrail groups. I am not a group but a private person, not even a scientist.
Mick West referred to my website. He thought that my main objections against contrails were cosmetic. He was also wrong there.

Spectrar Ghost wrote #389:

Withold was a poor choice of word on deirdre’s part. Without more detailed information your photos are interesting but can’t easily be slotted into the bigger picture. More regular photos would make real analysis possible.
Going about your photography in a systematic and thorough way can only help if your claims are true. You could show how many days contrails showed in your skies, and rule out synoptic scale meteorological conditions as a primary cause. You are, of course, free to continue as you have for the last two decades, but that seems to have failed to gain traction. Perhaps it is time to reasses your strategy.

Robert van Waning wrote #392:
My ‘claims’ are not more than suppositions, based on observation and logic. I never claimed to be a scientist. I started with saying that more research is necessary. The reactions on this forum strengthened me in this supposition.
Airplanes are everywhere and so are their exhaust fumes, consisting a.o. of water vapour and condensation nuclei. It seems logical to me that these behave as they always behave under comparable circumstances. It seems logical to me that changes in the troposphere have more effects on the weather and the climate than similar changes on groundlevel. It also seems logical that clouds that are produced by pollution are not there when there is no pollution.
Robert van Waning wrote #395:

The answer is yes if you broaden NASA’s definition of contrails to their stage wherein they are no longer visible to the naked eye from groundlevel. In that stage the water vapor and aerosols have not vanished completely out of the atmospheric system, as you seem to think. They keep floating all around the world at their original level of 10 – 13 km, only to descend after they have condensated or coagulated into bigger and heavier crystals or drops.
So, what is called ‘persistent spreading contrails’ is just a stage in the lifetime of aircraft exhaust.
The products or burning ‘liquid coal’ in the troposphere form together a layer of polluted air at high altitude that is saturated for ice because of the extremely low pressure and the temperature. That is why I call that layer an ‘ice curtain’: It is not visible so you can see your ‘clear blue sky’ right through it. That apparently makes you think that all the remnants of contrails are gone and vanished forever, never returning in new appearances to haunt us and following generations with their symptoms, effects and consequences.
I must keep on repeating that these are my suppositions, based on what I consider logical thinking which is based on what I have learned, observed and experienced.

Robert van Waning wrote #395:
[SR1419 had written: Is it logical to make this claim: “The pollution by airtraffic has more more effects on weather and climate than cars/trucks, industrial processes, heating of houses and buildings, production of electricity, etc.” based on nothing more than “random” observations?]
Again, the answer is yes. I suppose that the troposphere is essential in the processes of ‘making’ the weather and in our climate system.
[.. or this “permanent ‘ice curtain’ around the world”?]
Yes. See my explanation above.
[I have had weeks of clear blue skies above with me nary a persistent contrail…is there still a “permanent ice curtain” above me? How can it be permanent when the clouds generated are not permanent?]
What makes you think that the sky is ‘clear’? Because it is (a lighter shade of) blue? The ‘clear’ water of the Mediterranean Sea and of the Baltic Sea is (on sunny days) clear blue, but still those seas belong to the most polluted seas on earth.
What makes you think that the ‘persistent spreading contrails’ have indeed disappeared? Could it be that they have spread so thinly that you can hardly seem them anymore and that the the only indication of their presence is the lighter shade of the blue colour of the sky. You can often see the aviation smog if you look at the outer edge of the sun from under a roof or anything that blocks the sun itself:
#395 2015-8-11_11-55-33
[NO…planes are not “everywhere” – more hyperbole to sell your “suppositions”.]
There are not may places on earth anymore where planes to do not fly over, but even the sky high above those is permanently with remnants of the exhaust of airplanes. The contrails that come floating in over The Netherlands from the West, were made by planes that maybe flew over the U.K., Ireland or even the U.S.. Who knows?

Robert van Waning wrote #397:

NASA defines three kinds of contrails: Short-lived contrails, Persistent (non-spreading) contrails and Persistent spreading contrails (‘This is the type most likely to affect climate because they cover a larger area and last longer than short-lived or persistent contrails.’)
Tell me, please, what happens to the exhaust of airplanes after it has become ‘invisible’ (that is: to the naked eye from groundlevel)? And after that? Ad infinitum.
I ‘debunked’ chemtrails before you probably ever had heard of them
This is not a forum, but a community of aviation lovers and contrail defenders

Trailblazer wrote #398:
Nobody is “defending” contrails. Contrails are what they are. Artificial clouds which do have a measurable effect on the climate. But their appearance or non-appearance is nothing to do with pollution. Even aerodynamic contrails, which have nothing to do with engine exhaust, can persist and spread under the right conditions.

Robert van Waning wrote #400:

Ah, everything, even nitrogenoxides (NOx), carbon monoxide, hydrocarbons such as methane, sulfates (SOx), and soot and metal particles, becomes clear innocuous water.
Why are all of you so eager to deny that contrails are by definition caused by pollution?
And in what kind of cosmic dustbin do all the pollutants of aviation disappear?

Robert van Waning wrote #401:

Take today, for instance. How can you or anyone tell whether the hazy cirrus that is visible between the other clouds (cirrus and lower) is of natural origin?
Or could it be that components of the exhaust of aviation have played a part in its becoming visible (again)? So, isn’t that hazy ‘natural cirrus’ in fact aviation smog that became visible again after having been invisible for a longer or shorter while?
Who knows? You don’t and neither do I, but I do have my suspicions.

#401 2015-08-11 13.34.19
#401-2 2015-08-11 13.34.31
The filenames of the photos contain date and time, but these filenames are not shown, alas.
Spectrar Ghost wrote #402:
No one has denied that aircraft pollute. It’s obvious they do. Whether that 3% of CO2 load (and similar amounts of other pollutants since all hydrocarbons produce more or less the same combustion products) needs to be prioritized over power generation or auto travel is where I’d disagree.
I think it’s clear I meant the water content of the exhaust, since that is the only visible portion, in the form of contrails. NOx, and SOx are invisible; there is not enough soot to see at that altitude.
SR1419 wrote #403:

So, in other words if you just make things up to fit your bias the answer is “yes”.
By your logic, its cloudy even when its clear blue sky.
You are not “broadening” you are changing the definition in an attempt to force the data into your view.
Contrails- BY DEFINITION- are visible.

Robert van Waning wrote #404:
What bias? That airplanes pollute and generate clouds that grow and spread out and eventually get so thin that they are hardly recognizable anymore with the naked eye from groundlevel, you mean? That’s not a bias but a fact.
[By your logic, its cloudy even when its clear blue sky.]
By Jove, he’s got it! The awful but undeniable truth is dawning upon you, at last.
[You are not “broadening” you are changing the definition in an attempt to force the data into your view.]
At what stage does the definition of ‘spread-out persistent contrails’ end? When YOU cannot see them anymore? You don’t want to see them at all, so that is not a trustwothy criterium.
[Contrails- BY DEFINITION- are visible.]
Visible to whom and with what means?
But I agree that the defintion of NASA is not complete. It should comprise the stage of barely visible or recognizable aviation smog that makes the deep blue sky a shade lighter, milky blue.
SR1419 wrote #405:
Your bias is that contrails somehow represent a greater threat as pollution than all other point sources of pollution put together.
…and the bias that leads you to believe that a contrail exists even though you cannot see it.

Alas, no. The sky above me currently is a deep blue. No invisible contrails visible.

Huh? I love seeing contrails…been watching them for decades…Contrails “end” when the ice crystals sublimate and cease to become visible. Again, contrails- BY DEFINITION- are visible. If the contrail is not visible it does not exist. The soot particles and ice might even still exist just not in contrail form. They become a small part of the huge amount of aerosols already present in the atmosphere.

Visible to humans from the ground just as humans- and indeed NASA per your favorite definition- have defined contrails from the dawn of contrails.
The color of clear blue sky is subject to many variables including the human eye…looking at a clear sky and suggesting the color is affected by “recognizable” invisible material is not a logical supposition.

Landru wrote #406:
Well you could take time lapse photos over a day and tie them to a site like FlightAware to tie trails to potential flights and check weather conditions aloft for the possibility of contrail formation or the altitude of the cloud cover. But you don’t support your claims do you?
Robert van Waning wrote #407:
Don’t be ridiculous and try to be reasonable. Just like Deirdre you are telling me what I should do, without offering to pay me well for all the time-consuming professional work it would entail. I have taken thousands of pictures to support my doubts about the durability of aviation in view of its massive spillage of fossile resources and its impact on weather, climate and the quality and quantitity of the sun’s radiation that reaches the surface of earth. That is my contribution to what should be a heated discussion. Take it or leave it.
I had written: “Take today, for instance. How can you or anyone tell whether the hazy cirrus that is visible between the other clouds (cirrus and lower) is of natural origin? Or could it be that components of the exhaust of aviation have played a part in its becoming visible (again)? So, isn’t that hazy ‘natural cirrus’ in fact aviation smog that became visible again after having been invisible for a longer or shorter while? Who knows? You don’t and neither do I, but I do have my suspicions.”
That is not a claim but a question, dammit, supported by clear pictures of hazy shapes and patterns of clouds that could possibly have been made by airplanes many hours ago somewhere many thousand of miles away to the South, West, or any other direction, depending on the actual direction of the wind at 12 km high over the past couple of hours.Nobody can tie them to potential flights.
The weather conditions are clearly shown by the picture, however, and there is cirrus of all kinds and shapes. The question was: How can anybody know whether that cirrus is of natural origin or that the exhaust of airplanes has played a role in their development?
And what do you mean by supporting my ‘claims’ (that aren’t)? With something like this:
Content from external source:
[Driven mainly by continued economic growth and reduced fares, passenger traffic is estimated to grow at an average annual rate of nearly 5 percent during the period 2001–2020 (Airbus Global Market Forecast, 2002), making civil aviation one of the fastest growing industrial sectors.
Emissions of aircraft include carbon dioxide (CO2), water vapor (H2O), nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), a variety of hydrocarbons (HC), sulfur oxides, soot and other particles. Different aspects of the impact of aircraft emissions on the atmosphere have been identified, including changes in greenhouse gases, particles, contrails, and cirrus cloud formation (e.g. Fabian and Karcher, 1997; Brasseur et ¨ al., 1998; Penner et al, 1999; Schumann et al., 2000; Isaksen et al., 2003).

The main threat of aviation to the wider environment is believed to lie in its contribution to climate change. The present study deals with the impact of NOx emissions from aircraft, which, although representing only 1–2% of the total emissions of NOx from man-made and natural sources in the early 1990s (Lee et al., 1997), may have a pronounced impact on the chemical composition of the atmosphere. During the last three decades numerous studies have focused on the different implications of NOx emissions from aircraft (e.g. Hidalgo and Crutzen, 1977; Johnson et al., 1992; Schumann et al., 1997; Dameris et al., 1998; Kentarchos and Roelofs, 2002, Grewe et al., 2002a, b).
Most importantly, NOx emissions from aircraft are expected to increase ozone in the upper troposphere and lower stratosphere region (UTLS).

In contrast to all other major anthropogenic emission sources, aircraft emit their exhaust products directly into the UTLS, where pollutants have a much longer lifetime than at Earth’s surface, allowing excess nitric oxide and ozone to accumulate to larger and more persistent perturbations than at Earth’s surface. These factors, combined with the relatively large radiative forcing caused by ozone increases occurring in the UTLS (Wang and Sze, 1980; Lacis et al., 1990; Hansen et al., 1997), make aircraft NOx emissions disproportionately important to the total O3 radiative forcing from all sources.]

Or this:

Rapid increase of aircraft emissions could affect atmospheric ozone and climate in the future
Leading European researchers have concluded that aircraft emissions are small in comparison to all other man-made emissions, but could be significantly affecting atmospheric ozone and cloud cover with possible implications for climate change. These are the conclusions of a comprehensive review of the current state of knowledge carried out at the initiative of the European Commission and published today in the scientific journal “Atmospheric Environment”.

The authors of the review, entitled “European Scientific Assessment of the Atmospheric Effects of Aircraft Emissions”, which relies heavily on the results of successful European [1]and national [2] research programmes, conclude that:

  • The 20-50% increase in the NOx abundance caused by aircraft traffic in the vicinity of their cruising altitude (10-12 km) has produced a 4-8% increase in the ozone concentration of the upper troposphere (maximum value during summertime) where ozone is a strong greenhouse gas. The warming effect associated with this ozone increase is comparable to the warming effect of CO2 emitted by aircraft (about 2-3% of all anthropogenic CO2 emissions).
  • Climate perturbations could also have resulted from the formation of persistent contrails and high-level cirrus clouds produced in the busiest flight corridors. Additional effects on the radiative balance of the atmosphere could have been generated by the soot and sulphur particles released by aircraft engines. The warming effect of the changes in cloudiness is more difficult to assess but appears to be also of the same magnitude as the warming effect of CO2 emitted by aircraft.
  • The total climate forcing caused by the present fleet of commercial aircraft (about 0.1 Wm-2) is a small contribution to the total forcing (2.4 Wm-2) associated with past industrial development. However, with air traffic in the next 20 years expected to grow faster than the global economy, the relative contribution of aviation to environmental changes (pollution, stratospheric ozone, climate) could become more significant, unless new, less-polluting engines and more fuel-efficient aircraft technologies are introduced.
  • The development of a fleet of supersonic aircraft flying at high altitudes (17-20 km)could perturb the ozone layer in the stratosphere. Current models indicate, however that changes in the ozone column produced by a hypothetical fleet of 500 aircraft would be just a few percent and should lead to changes in the UV-B level at the Earth’s surface of less than 2%. However, more research on the complex and poorly understood processes that affect the chemistry of ozone in the lower stratosphere is required before a conclusive assessment can be produced. [/EX]

Did you read that: ‘.. could .. ‘, ‘ .. could ..’, ‘.. could .’?

Why don’t you ask those ‘leading European researchers’ to support their claims?

Landru (moderator) wrote #408:
You made claims so I’m asking you. If you can’t support your claims don’t make them. You spend a lot of time typing here why not spend it supporting your claims. It’s pretty easy to tie contrails to flights as has been shown elsewhere on this site. You don’t even have to be a scientist.
Robert van Waning wrote # 409:
That is not a bias but a generally recognized fact, because of the location where worldwide aviation daily spews out the undesirable products of burning massive amounts of kerosene: straight into the troposphere.
[…and the bias that leads you to believe that a contrail exists even though you cannot see it.]
Your bias is that something that you cannot see, does not exist.
{The sky above me currently is a deep blue. No invisible contrails visible.]
That does not mean that high up there is not a layer of exhaust vapour and particles that have partly condensated or could do so at any moment that the conditions of the environment (temperature, pressure, humidity) change.
[I love seeing contrails…been watching them for decades…]
That’s what I thought: You are a bunch of aviation lovers, defenders of the Holy Contrail.
[Contrails “end” when the ice crystals sublimate and cease to become visible.]
And after that? What stops the cloud condensation particles from acting as such again, and again, and again, etc.?
Or do you think those particles and the water vapour disappear, just like that, into thin air, literally?
[Again, contrails- BY DEFINITION- are visible. If the contrail is not visible it does not exist.]
And how do you define ‘visible’? Some humans on the ground simply do not want to see aviation smog.
[The soot particles and ice might even still exist just not in contrail form. They become a small part of the huge amount of aerosols already present in the atmosphere.]
Exactly, and that amount of aerosols and soot grows daily by the ever growing number of (too cheap) flights all around the world. People take their own car on the plane to their holiday address. Things are getting more ridiculous and irresponsible all the time.
This circus might lead to a permanent cirrus cover and that is why I am worried.
[The color of clear blue sky is subject to many variables including the human eye… looking at a clear sky and suggesting the color is affected by “recognizable” invisible material is not a logical supposition.]
Aviation smog is in the eye of the beholder. I would see it where you wouldn’t.

Robert van Waning wrote #410:

Gosh. Look at the pictures! Those vague, hazy shapes and patterns of cirrus clouds might have been caused by flights that have taken place many hours ago somewhere at a distance of thousands of miles in some unknown direction, North, East, South of West or somewhere inbetween. Again: be reasonable.

Robert van Waning wrote #414:

I wrote: “How can you or anyone tell whether the hazy cirrus that is visible between the other clouds (cirrus and lower) is of natural origin? Or could it be that components of the exhaust of aviation have played a part in its becoming visible (again)? So, isn’t that hazy ‘natural cirrus’ in fact aviation smog that became visible again after having been invisible for a longer or shorter while? Who knows? You don’t and neither do I, but I do have my suspicions.”
That is not a claim but a question. My suspicions are based on what I have learned, experienced and photographed. If you do not find them convincing, that’s just too bad. If even leading scientists do not have all the answers yet, how could I? That is why I wrote in the beginning that far more research has to be done. This community of aviation lovers is not even convinced of that necessity.
I have replied to the original question whether there are any anti contrail groups. Apparently this forum just wants to wipe them out completely by nagging.
Let’s call it a day. Bye.

SR1419 wrote #415:

If its a generally recognized fact than it would be easy to produce evidence of your “supposition”
As it stands, its just your biased opinion based on nothing more than non-scientific “random observations”.
Now, would be the time to produce evidence of your claim…otherwise you are tilting at windmills 30K feet up

Robert van Waning wrote #417:

Robert van Waning wrote #419:

SR1419 wrote #420: you are just trolling…we all know contrails sometimes turn into cirrus clouds…and as the paper you linked suggests “MAY” (as in might, maybe and indeed not a fact that it will) effect the climate…
But no where does that paper or any other research on contrails even remotely suggest that:

It clearly is NOT a “generally recognized fact” that contrails represent a greater threat as pollution than all other point sources of pollution put together.
Your supposition is tainted by your bias.
Good luck with that.

Robert van Waning wrote #421:
Contrail can indeed turn into cirrus clouds or they can ‘disappear’. That is: they become (temporarily) invisible. My question was what happens to those componenents that made them visible in the first place. I think they can assist in another condensation process, later and somewhere else. By that time and at that place they are no longer recognizable as products of aviation. That is the point I am trying to make, without any scientific proof, as yet.

I did NOT say ‘put together’. I meant each apart. The relatively geater influence has to do with the facht that aircraft spew their exhaust fumes and particles straight into the tropopause. These cloud-making components are not gradually brought up there by convection.

Robert van Waning wrote #423:

Because it is logical, physically unavoidable, and practically undeniable. It confirms what I know, expect and observe.

On what may look as a day with a ‘clear blue sky’ aviation smog can only be recognized by looking at the edge of the sun:
#423-1 2015-08-13 15.53.46

Or by ‘suspecting’ certain shapes and patterns:

#423-2 2015-08-13 16.49.41

Robert van Waning wrote #424:
[SR1419 said: …and yet none of the papers you quote suggest that your supposition is a “recognized fact”. So, why do you?]
Content from external source:
To understand the possible aviation impact on clouds, it is important to distinguish two effects.
Direct effect (contrail-cirrus).
Linear and spreading contrails, initially formed from exhaust water vapor and particles, constitute and additional cloud type and enhance cirrus cloud coverage. Initial contrail occurrence relies on well understood thermodynamic principles, initial contrail properties depend on soot and sulfur emissions and near-field exhaust (jet/vortex) dynamics. The spreading process of persistent contrails is controlled by wind shear and relative humidity. Contrail-cirrus are advected with the wind field over large distances, even into regions without significant air traffic. The direct effect is largest in regions without background cirrus.
Indirect effect (soot-induced cirrus).
Soot particles associated with aqueous coatings of sulfur and organics are emitted together with gaseous sulfur oxides and may perturb cirrus formation processes and cirrus coverage on regional scales. The perturbation depends on the ice-forming ability of coated soot particles that interact with ambient air, on the ability of other atmospheric particles to form ice, and on dynamic processes that set the stage for the generation of cirrus clouds in supersaturated regions.Coagulation of soot and sulfur particles in diluting aircraft wakes changes the size distribution and the chemical composition of aerosol particles available for freezing. The indirect effect is less important in regions where cloud forms on more efficient ice nuclei than aircraft soot.
It is important to recognize that contrail-cirrus also imply an indirect effect on cirrus. If cirrus clouds form in the presence of aged contrail-cirrus, the cirrus may have different properties because its crystals nucleate in regions with preexisting ice. When embedded in background cirrus, contrail-cirrus may compete with background cirrus for the available water vapor, altering its microphysical and optical properties.
[SR1419 said: .. and the bias that leads you to believe that a contrail exists even though you cannot see it. [..] The color of clear blue sky is subject to many variables including the human eye…looking at a clear sky and suggesting the color is affected by “recognizable” invisible material is not a logical supposition.]
Content from external source:
It is important to recognize that contrail-cirrus also imply an indirect effect on cirrus. If cirrus clouds form in the presence of aged contrail-cirrus, the cirrus may have different properties because its crystals nucleate in regions with preexisting ice. When embedded in background cirrus, contrail-cirrus may compete with background cirrus for the available water vapor, altering its microphysical and optical properties. ]
Robert van Waning wrote #426:
The reality apparently is painful for aviation lovers, Defenders of the Holy Contrail. You cling to the tiniest straw, just to take the blame away from your precious airplanes. Just keep on dreaming of exhaust of airplanes without soot and other (much smaller) particles.
SR1419 wrote #427:
Again, none of the papers you have linked have suggested the effects of contrails are any where near the supposed magnitude you Believe. Indeed, none of them state the indirect effects of contrails are a fact…only you do that.
Ad Hom attacks and name calling only serve to highlight the deficiencies in your argument. Everyone in this thread knows airplanes emit soot. We just don’t fear it as much as you do.
Robert van Waning wrote #428:
The only deficiency in my argument is that a lot of research still has to be done, just as I had written in the beginning. I expect that research to confirm my worries.
Robrt van Waning wrote #430:
Speculations? As you are in complete denial, you haven’t even read the texts that I included to corroborate my suppositions:

Do you really want me to continue with giving texts that make shambles of your stubborn opposition to logic? That would not have any sense as you simpy refuse to accept an inconvenient truth.

Robert van Waning wrote #431:

Here is more ‘speculation’:

Trailblazer wrote#432:
You are preaching to the choir Robert. We know all this stuff. Planes make cirrus clouds. Cirrus clouds warm the planet. Tell us something we don’t know. You seem to think we are denying or defending this. We’re not. Contrails are just one very small part of the many ways that mankind affects the atmosphere.
Focusing on contrails rather than the bigger picture shows a very strange lack of perspective. It’s like complaining about the pollution from the exhaust pipes of the cars that people drive to work at a coal-fired power station.
Robert van Waning wrote #433:
The thing is: I do not think aviation smog plays ‘a very small part’ in influencing the weather, the climate and the quality and quantity of the sun’ radiation that reaches the surface of earth. That is where we disagree, but we both lack the conclusive proofs of our supposition. Mine is based on the composition of aviation-induced cirrus (water vapour in combination with cloud condensation particles) and the place where it is daily and worldwide dumped in great quantities, namely straightaway in the tropopause.
I think we can stop here, unless some member of your community comes up with something that I cannot let pass.
SR1419 wrote #434:
You’re not really listening Robert- your too busy getting defensive- all your links-(most of which I have read before) simply show what we already know. Planes can make cirrus clouds. None of them definitively quantify the effects these cirrus clouds have weather and climate, none of them suggest these clouds have as much impact on weather and climate that you Believe. This not me being in denial, its me looking at the facts.

But you purvey your supposition as a “recognized fact”- That is illogical and suggests emotional bias.

TWCobra wrote #436:
Robert, aircraft contribute a tiny fraction of the water vapour in a contrails. The rest was already there. The Knollenberg report found that water contained in a contrail was 10000times the amount emitted in the exhaust. Therefore you are vastly overstating your case.

Robert van Waning wrote #437:
Aircraft contribute daily and worldwide a combination of water vapour and condensation particles straight to the delicate balance of the tropopause.
Apparently the continuous exhaust of thousands of aircraft tips a balance, and that is what weather, climate and – in general – life are all about. Without exhaust, the contrails and aviation-induced would not have been there, and the same goes for all their probable effects and consequences.
TWCobra wrote #438:
You haven’t addressed the point. You claimed that jets add “great quantities” of water vapour. Yet a 747 only adds approx 13 cubic metres of water vapour per 1000 kilometres of flight.
You are neglecting the fact that hundreds of millions of cars do the same thing; burn hydrocarbons which creates water which goes into the troposphere.
I say it again.. You are overstating your case.

Robert van Waning wrote #440:

Whether 13 cubic meters of water vapour is much or not depends on the environment where they are dumped, unfiltered. In this case that is the tropopause where unfiltered burning of kerosene should be forbidden.
Again, you ignore the particles that are so vital to the successive condensation processes in which they assist.

[You are neglecting the fact that hundreds of millions of cars do the same thing; burn hydrocarbons which creates water which goes into the troposphere.]
I was talking about the tropopause*), not the troposphere.
[I say it again.. You are overstating your case.]
Do I ‘overstate my case’ by taking thousands of pictures of aviation-induced cirrus and expressing my worries about their probable (because logical and physically unavoidable) effects and consequences?
Aren’t you all being a bit oversensitive? Tell me more about your ties to the aviation industry. You sound like a lobbyist to me.
Anyway, I resent being attacked and accused by anonimous people with false names (and maybe even false ‘selfies’) who do not even have the courage to take personal responsibility for their utterances.

Robert van Waning wrote #441:

How probable do you think it is that they have no effects and consequences? And what ‘magnitude’ do you think I believe in, anyhow?
[You purvey your opinion as a “recognized fact” when its not.]
So do you, so please stop repeating yourself ad nauseam.

Mick West (Administrator) wrote #442:
This thread appears to be going round in circles, and has been closed. Fee free to continue discussion via PM/Conversations.
30 December 2015, 10:30h



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