There are those who claim that the trails we see behind aircraft high in the sky are not the normal condensation of water vapour from the hot exhaust gases but are in fact chemicals that are being deliberately sprayed upon us by government agencies for some dark and sinister reasons. When asked to prove their claims, however, their response is invariably either just a video or blog of someone else making the same unsubstantiated claim, or a simple “Well why don’t you prove that they’re NOT chemtrails!”. Proof has been given time and time again but ok, here it is one more time, using only sound scientific methods and no political mumbo-jumbo.
Actually, it should not be for me or any reasonably-minded person to reprove something that has always been a normal and scientifically-accepted fact of life. If others come along and claim that it is something totally new and different then it is actually up to them to provide evidence that proves beyond doubt that the original theory is wrong. The simple fact is that this evidence does not exist, but this does still not deter them from making these claims and denouncing anyone who tries to argue against them. I am not denying that geo-engineering, still just a theoretical exercise, could be easy enough to try out, given the right modifications to an appropriate aircraft, or that cloud-seeding experiments have been carried out (but these only consist of silver iodide crystals from burning flares and not actual dumping of material). I am actually totally against the whole idea of trying to geo-engineer our way out of what is really not a problem, in my opinion. What I AM denying is the claim that the trails we see from normal commercial airliners, both with our own eyes and in the photos of our readers, are chemtrails, as is claimed by a certain number of conspirators every time a reader shares a photo with us. Using such sites as Flightradar24.com it is so easy to check at any minute of the day what planes are flying overhead, generating the contrails we are seeing. To claim that these planes are not just innocent airliners but are being used for dumping harmful chemicals requires specific proof. Has anyone ever seen a refueling truck loading anything other than fuel into the tanks as you board a plane? Have you ever spotted nozzles on the wings spraying these chemicals as you look out the window as you fly along? Do you think the airlines are in on this and agree to carry the extra weight of these substances?
No, didn’t think so.
Anyway, what are contrails (CONdensation-TRAILS)? They are plumes of ice-crystals formed by the condensation and freezing of water vapour in the exhaust-gases of an aircraft flying at high altitudes and under the right conditions. As fuel (petrol, diesel, avgas, Jet-A1, kerosene, natural gas, etc.) is a hydrocarbon, burning it produces carbon dioxide (CO2) and water vapour (H2O), along with other materials such as nitrogen oxides, sulphates, hydrocarbons, soot, metal particles, etc. This applies to planes as it does to trains, cars, trucks, buses, motorbikes, lawnmowers, boilers, etc. Different fuels contain different additives and produce different levels of these by-productss, but they all produce CO2 and water vapour. That is basic Junior Cert chemistry and something that cannot be denied. The difference with planes is that they operate in conditions very different to these other vehicles.
I am now going to take the main arguments that the conspirators use in their claims that the clouds we see can not be simple contrails, and will give a scientific explanation of why they are wrong and what is actually happening. In each case I will first give some simple analogies to illustrate the reason, then give a deeper scientific explanation. That way no one can claim it’s above their comprehension. But first, some definitions:
Dewpoint: The temperature at which condensation (fog/cloud) will occur if air is cooled enough. Humid air has a higher dewpoint than dry air. The relative humidity is 100% when the dewpoint and temperature are equal.
Relative humidity: The amount of water vapour in the air, expressed as a percentage of the total amount of water vapour the air can hold at that temperature and pressure. Warm air can hold a lot more vapour than cold air. 100% means the air is totally saturated and condensation (fog/cloud) will form.
Conspiracy Claim 1. “Contrails only last for seconds but these ones lasted for hours, therefore they must be chemtrails”.
ACTUAL REASON: Contrails can last from seconds to hours, depending on the relative humidity at cruising altitudes. If it is above around 70% then the contrails can last for hours.
ANALOGIES: In summer you don’t normally see your breath, in cold winter you normally do. In summer you don’t see truck exhausts form water vapour clouds, in winter you
normally do, and they can last for relatively long times (especially in places like Siberia). If you throw a saucepan of boiling water in the air in summer it will
simply fall to the ground as water, with some of it evaporating on the way. If you do the same in winter (below around -20 °C) then it will freeze instantly into a cloud of fine ice particles and hang around a for much longer. This video illustrates this perfectly. Seen from below we see the larger ice-particles falling quickly to the ground but the main cloud of tiny crystals remains suspended and drifts slowly, just like a contrail.
THE SCIENCE: Many days we don’t actually see any trails at all from aircraft flying high above us as the trails dissipate as soon as they are formed. The air at cruising altitudes is very cold (-40 to -60 °C) and usually very dry (low relative humidity). The water vapour from the exhaust gases alone is not enough to form a contrail. Knollenburg (1972) gives a breakdown of typical components of aircraft exhaust gases, with around 1.37 kg of water vapour released per kg of fuel burned. The study found that exhaust gases contained around 1.7 g of water vapour for every metre flown, but found actual persistent contrails to contain at least 30,000 times that level (20,700-41,200 g per metre). This means that the overwhelming majority of the water in contrails comes from the atmosphere, with only around 1 in every 30,000 molecules originating from the burning of the fuel. It is therefore clear that relative humidity at cruising altitude needs to be relatively high for contrails to form and be visible, and very high (above around 70%) for them to persist for long periods.
We get these conditions from time to time and place to place, especially a few hundred miles ahead of an approaching depression (warm front), and to the west of an upper ridge-axis, among others. We normally see natural cirrus clouds (thin, high, wispy clouds) in these conditions, but even when conditions are not quite humid enough for natural cirrus to form on their own they can be right for contrails, as the exhaust particles (soot, etc.) act as cloud condensation nuclei (CCN) around which water vapour can condense and freeze into ice-crystals. This is why we can sometimes see contrails without natural cirrus, but normally we would see some cirrus too, even if just a few random wisps. If the relative humidity is below around 60% then the ice-crystals can sublimate (turn from solid directly to gas) fairly quickly and dissipate but if it’s above around 70% this sublimation process is much slower and the contrail can last for hours. Contrail ice-crystals are also much smaller (0.001 – 0.1 mm) than cirrus crystals (0.01 – several mm), which allows them to remain suspended for longer.
Conspiracy Claim 2. “I saw two aircraft flying in the same area. One aircraft’s contrail dissipated within a few seconds, the other’s grew and lasted for hours. The second aircraft was obviously spraying chemicals”.
ACTUAL REASON: They were simply flying at different altitudes and/or were different types of aircraft (engine).
ANALOGIES: Your bathroom mirror doesn’t fog up when you first take a shower. It only does so after a while, when there is enough vapour in the room to increase the dewpoint to the temperature of the mirror, allowing the vapour to condense onto.
A small cup of coffee makes a smaller steam cloud than a large open pot of coffee. The pot has a larger volume of steam rising and condensing off it, which rises to a greater height before evaporating, just as a larger engine produces more emissions than a smaller one.
THE SCIENCE: Cirrus clouds are very high up but relatively thin (sometimes only a few hundred metres deep), therefore there is only a narrow layer in which conditions are right for their formation. The same goes for contrails. Two identical aircraft flying at different altitudes can therefore produce very different contrails as the temperature and humidity can be very different.
Look at this sounding (plot of temperature, dewpoint and wind measurements from an instrument attached to a weather balloon) for Camborne, in the extreme southwestern
tip of England, around the middle of the day on August 22nd, 2013.
Airliners cruise at between around 30,000-40,000 ft (9,000-12,000 m). The sounding shows cold and mainly dry upper levels (the temperature and dewpoint curves are far apart), however there is a very thin humid layer just below 300 hPa (9,500 metres), where the dewpoint curve (left) shoots over to almost meet the temperature curve (right), meaning high relative humidity. We would expect very few contrails in this scenario as only those planes flying exactly within that humid layer will produce contrails. Other layers are just too dry. The actual data points from this sounding show that humid layer to be at around 9,116 metres (around 30,000 ft), with a relative humidity of 78%. Sure enough this high-resolution MODIS satellite picture for 11:40 UTC (around 20 minutes before the sounding) shows just one fresh contrail just south of Lands End, which FlightRadar24.com shows as United Airlines flight 43, a Boeing 767-400 flying at 30,000 ft. It shows dozens of other aircraft at different heights all over southern England and the English Channel, but not one of these is producing a contrail as the levels they’re flying at are too dry. Not surprisingly they’re not producing chemtrails either!
Sometimes we see broken or very short contrails, i.e. with breaks, as in my photo at the top of this article. This can be caused by an aircraft climbing through a humid layer, or by the effects of gravity waves at altitude. The plane enters and exits humid areas as it flies along, given a broken contrail. We also see this type of effect with natural transverse cirrus bands along which form perpendicular to the jetstream flow (strong winds at altitude). An aircraft flying parallel to the jetstream will be passing in and out of the humid areas that are causing the transverse cirrus, so its contrail will be discontinuous.
Two different types of aircraft flying at the same altitude can still produce different contrails. Different engines produce different-sized exhaust plumes, and newer engines produce cooler exhaust-gas temperatures than older engines. Cooler exhaust temperatures allow the contrail to form quicker, before the gases have a chance to mix with the ambient air, as the gas needs less time to cool to condense the vapour into ice-crystals. Engine contrails can also be affected by the aerodynamics of the aircraft wings, etc., and even the weight of the aircraft, which can strengthen wake-vortices and enhance contrails. In fact, some contrails are not even related to the engine exhaust gases at all and are merely condensation formed withing the wake-vortices, where the pressure is locally lower than the surroundings. We can see that when landing or taking off on a very humid day.
To an observer on the ground it can be very difficult to accurately estimate the relative heights of two aircraft flying near eachother. They may SEEM to be at the same altitude but in reality they could be a few thousand feet apart and therefore in possibly very different ambient conditions.
Conspiracy Claim 3. “Those trails are in regular criss-cross patterns, so there is obviously some systematic spraying going on”.
ACTUAL REASON: Planes fly many different routes (called airways), which can cross eachother at points called Intersections.
ANALOGY: No need for one here, it’s pretty straightforward!
THE SCIENCE: Ireland’s airspace is very busy with transatlantic traffic, with hundreds of morning eastbound and afternoon and evening westbound flights every day. Ireland has actually done away with the upper airway system within its airspace, instead allowing aircraft to fly their own direct routes between intersections along the eastern and western borders of the airspace. This saves the airlines time and fuel, but also means no real set published flight paths, as there used to be previously. Planes cross paths all the time, depending on what the intersections they are flying between. Just off the east coast these flights all converge at a few intersections, which can give a more regular contrail pattern to an observer on the ground. The link above also shows the complexity of the airway system over the UK airspace and this video shows how busy traffic gets throughout different times of the day, especially the afternoon and evening in Europe.
Conspiracy Claim 4. “I never saw this many contrails when I was a kid so it must be chemtrails that I’m seeing now”.
ACTUAL REASON: There are more flights now than years ago. Engines are larger and produce cooler exhaust gases, which make it easier for contrails to form, as explained
ANALOGY: A room full of kids is a hell of a lot louder than a room with just one kid!
THE SCIENCE: Pretty much explained in the other points above. We should not, however, compare what we are seeing now to what we remember as kids. We all think that the
summers were better back when we were young, but there are no data to back this up. Our minds as kids were different to what they are now, having developed through all
the stages of cognitive development. In the same way, we were most likely not counting contrails back then and wouldn’t have probably noticed them much in any case.
Conspiracy Claim 5. “Children have lots of respiratory problems now and it’s due to chemtrails”.
ACTUAL REASON: This has to be the craziest claim I have heard from a conspirator. There are many more plausible and well-documented reasons for children’s health problems. The use of a sick child as proof of chemtrails is stooping to a new low.
THE SCIENCE: The science of the previous explanations debunks this claim as it proves that the chemtrails are not there in the first place. Increases in children’s health problems are well-documented and can be due to increased obesity, poor diet, less excercise, more time spent indoors, etc.
Satellite imagery is a perfect tool for spotting contrails. Visible imagery is good, but there are other types of imagery (IR, Water-vapour, RGB, Dust RGB, etc.) that show them up to varying degrees. These images are formed by filtering various wavelengths, which show up differences in cloud physics, such as small or large ice-crystals, thin or thick layers, etc.
The Eview image below of the Iberian peninsula at 1800 UTC this evening shows an area of persistent contrails over Biscay and the northern and northwestern parts of Spain and Portugal, with none showing up elsewhere. Comparing this image with the predicted 300 hPa relative humidity chart from the GFS model (underneath) shows that the contrails are forming right inside the area of >75% relative humidity, which stretches from the Pyrenees to central Portugal and up to Galicia. Other areas are too dry for contrails. This is a good example of how we can actually predict the areas that will have contrails.
It only requires one test to prove a theory wrong, but in this article I have given several. Sometimes we see things that we cannot explain. Various theories circulate to try to explain them, and invariably some of these theories take on a political theme – a Them versus Us kind of thing. Some people are more prone to accepting these theories than others, and a quick check of the Facebook profiles of many of the conspirators on our page will confirm that. This has been an effort to explain why their chemtrail theory is false on so many levels, and maybe some of them will finally see the light and accept that science rules over our imaginations 100% of the time. I can, however, forecast even now the responses I will get to this article, as some people just want to believe in the alternative, for whatever reasons. I can do nothing about that. We are all different, but ignorance is no excuse for stupidity at any time.
Fergal – Irish Weather Online