An old letter titled, "THE CHEMTRAIL FRAUD" that I posted to the Coast to Coast AM radio program on June 17, 2008; it bears repeating here and now because the chemtrail thing just never seems to die.
Sorry that I worded the title so harshly, but I really can't characterize this controversy any other way in good conscience. After listening to the show this morning and then surfing the Web looking for information about chemtrails, I came to a site called http://educate-yourself.org/ct/ and some other links thereto and found what I unfortunately suspected -- a lot of blatantly false information and misrepresented photos about what are -- for real, honestly, hand to God, I swear -- CONTRAILS.
To recap what a contrail is, picture yourself in one of our modern passenger jet aircraft flying over, say, Missouri. While you are sitting and relaxing, reading a book, or if you happen to be terrified of flight, white knuckling and staring out the window hoping the engines don't fall off in mid-flight, you look out and happen to notice that behind the jet engine on your side of the plane is a white vapor appearing a certain distance behind the engine. You ask the stewardess what that is, and she says "Oh, that's just the contrail." She gives this explanation so glibly that it's as if you are supposed to be satisfied with that information, but the word itself means nothing without a definition.
Here's one from Merriam-Webster online: "streaks of condensed water vapor created in the air by an airplane or rocket at high altitudes." The most important thing to get out of this is the content of a contrail is WATER. And water does certain things under certain conditions. At certain altitudes, under what weathermen call saturated conditions, it condenses into a cloud.
Now, before I go into explaining what saturation of air is, let me first go into my background as a recently graduated auto mechanic trainee and discuss what actually comes out of an airplane engine exhaust. Air and fuel are mixed for combustion, in order to provide thrust for the aircraft, at a given ratio which is known as the stoichiometric ratio. Stoichiometric just means that the ratio is the correct ratio for the type of fuel used and the oxidizer used to combust it. For gasoline, for example, the stoichiometric ratio of air to gasoline is 14.7 to 1. For methane, it's a lot higher, about 37.6 parts air to 1 fuel. For jet fueled engines it's technically about 15:1, similar to gasoline, however additional air is added to flow through the engine to cool the turbines because otherwise they overheat. The end result of this is the same regardless of the hydrocarbon-based fuel used -- you get energy production and waste products, which under the best combustion conditions yield some carbon dioxide and a much greater amount of water. There are also traces of unburnt hydrocarbons and if the reaction is too hot or too lean, some nitrous oxides as well, but the vast majority of the waste generated is primarily water vapor, secondarily carbon dioxide. This comes out the tailpipe of your car, and mixed with uncombusted coolant air, it comes out the back end of a jet engine.
Now about saturation -- this is an atmospheric condition which occurs when the humidity level -- the percentage of water vapor the air can hold at a given temperature -- is up close to 100 percent. This occurs when the dew point of air is close to the actual air temperature, and the dew point is a more direct measurement of the actual water content of the air. Now there are a few things to remember about this -- one is that the dew point can vary considerably depending on the overall weather conditions, and another is that temperature changes do not translate to dew point change or vice versa, except when air temperature falls into or below the dew point, thus forcing condensation to take place.
So here we go -- hot gas at some hundreds of degrees comes out the back end of the engines on our passenger jet. This hot gas is mostly air, with water vapor and carbon dioxide. The CO2 doesn't affect the formation of clouds so we can ignore that, it's invisible and inert. The hot air coming out of the engine may have a dewpoint of, let's say, 30 degrees Fahrenheit. In gas that's 200 plus degrees it appears to be very dry air, and you do not see vapor forming at that point. However, the air at a high altitude may be as cold as -50 deg F, with a dew point of -60 F. In those conditions you could have a bright clear blue sky without a cloud in it, since the temperature is still 10 degrees away from saturation. However, with the plane passing through it, now you have this part of the air heated to 200 degrees, with the dewpoint rising past 30 degrees as the engine's exhaust water is added to this part of the air. Very soon, the air temperature returns to ambient (what it was before the plane passed through it.) But the dewpoint which was at -60 F has now been raised over 90 degrees in that parcel of air!
Upon cooling down below 30 degrees vapor forms as the air is now saturated and cannot hold the moisture as vapor, it has to condense. By the time the air temp has dropped below -40 the condensation has already frozen into ice particles. These form the contrail that fans out behind the plane as wind currents push and pull at the trail. Now, with the dew point around the trail (not in it) still about -60 F, the ice particles which have formed a pretty dense contrail begin to evaporate into the surrounding air. However, they will normally take hours to do so because the dewpoint is not very low for that altitude and ice takes longer to evaporate than water droplets do. So basically the plane has done nothing more or less than create a type of cirrus cloud, and cirrus happens to be a kind that can hang around for days given the right conditions.
Now I can tell you, on my honor as a weather buff of 25 years with some courses under my belt in the field, experience taking weather readings, and studying the subject on my own time, that all of the pictures I have seen of trails in the sky are contrails. It seems extremely unlikely to me that if nefarious organizations could even pepper the sky with noxious powders and whatnot, that they would give away their activities by using substances that reflect as much light as a cloud -- and by the way most aerosols are invisible to the human eye, including volcanic ash below certain concentrations and sizes and most dust. Also, given the vast scale of the atmosphere and the complexity of wind patterns in it, it seems very very unlikely to me that high altitude spraying would have any meaningfully intentional consequences on any ground targets. Effective spraying has to be done at as low an altitude as safely possible, to limit the area covered and to ensure that the area you WANT to cover is reached by the sprayed contents.
Now about the photos -- some of them show contrails that can form at midlevel altitudes in saturated conditions where the contrail is a cloud of water droplets, too warm to freeze. These contrails will last just as long as any of the other streetlike clouds (altocumulus or altostratus) that may be in the vicinity, and they can be fairly thick for a while, again depending on saturation conditions. Other trails seen in photos, notably the ones with "rainbow effects," are no doubt higher altitude ice particle trails. What happens here is the light from the sun hits a certain angle from the viewer or photographer, and the ice particles scatter the colors in it forming a rainbow or a sun dog, from the viewer's perspective. Same thing happens in cirrus clouds -- it's not magic and it's not chemically induced, it's a property of the optical physics of water. Ice particles are more highly reflective than liquid cloud droplets, so you will tend to see that more often in ice particle trails, though it's also possible in droplet trails.
Certain photos show crisscrossing trails as well. This is common because air travel routes do often cross over each other, usually at different altitudes (when air traffic controllers are doing their jobs, which we like to think is all of the time.) You will probably see this sort of thing a lot in regions between several airport hubs.
I hope this helps to clear up the contrail mystery somewhat. :)