A newbie who tried to learn about chemtrails will sooner or later suggested to visit contrailscience.com. It is a website that is build solely to debunk chemtrails. The owner is Mick West, a known chemtrails debunker. He also has another website, metabunk.org, a forum for all the debunker.
In the about page, the owner mention:
"ContrailScience.com is just a place where I write about both contrails and science – which also includes some looking at the “chemtrail” theory, and the pseudoscience associated with it.
My name is Mick West, I have private pilot training up to long distance solo certification, and have flown a 150 mile solo flight. I’ve been training out of Santa Monica airport, so I know the airspace round here. I like writing, and figuring things out. I’ve been writing about contrails and the “chemtrail” theory since 2007.
I’m not a scientist, or a meteorologist, but I try to ensure that what I post is comprised of independently verifiable facts. You can check these facts yourself. If you find ANY error on this site, then let me know and I will issue a correction immediately."
The last statement is interesting because I did try to correct their mistake by posting a link to a legitimate site explaining the real science behind contrails, but my comment is never approved. So the last statement is a lie.
Then the statement about independely verifiable fact. This also raise another question because most of the article in that website would not include link for people to verify the fact. I will some example of evidence that deny that statement.
Let us start with the article in main page of that website.
"Contrails Through History
Theorists claim: Contrails used to dissipate in a few seconds, minutes at most.
But they didn’t. There’s a huge amount of evidence (in addition to lots of people remembering persistent contrails). It dates back to 1918, and continues up to the present day."
What is not mentioned by the writer is contrails in science usually mention jet exhaust. Plane before jet era produce a lot of particle (smoke) that will produce much more vivid trails. The plane at that era will produce smoke even on the ground, something you would not see today on jet engined plane. The smoke that old plane release will become the seed of thick contrails at high altitude. Today, contrails indicate the amount of particle pollution that the engine produced.
The article posted at 5th March 2013 mention:
Hybrid Contrails – A New Classification contrails
Contrails are generally classified into two types. Exhaust contrails and aerodynamic contrails.
Exhaust contrails are formed by the mixing of the hot humid exhaust of the engines with cold humid surrounding air, creating long streamers of clouds. If the conditions are right then these can persist and spread. These are the most common type of contrail observed."
Exhaust contrails happen because the aircraft exhaust emit particle. The particle is the important part during the creation of contrails. Here is what science mention
J. Schneider & Chr. Voigt - Physics and Chemistry of Aerosols and Ice Clouds, Chapter 8: Contrails and contrail cirrus (mirror link)
• Contrails consist of ice particles that nucleate primarily on aerosols emitted or formed in the plume.
• At initial stage contrails grow by deposition of exhaust water vapor.
• Later during their life cycle contrails grow by deposition of entrained ambient water vapor.
• Formation of contrails due to increase in RHI during isobaric mixing of the hot and humid exhaust gases with colder and less humid ambient air.
"• Aircraft influence high clouds indirectly by injecting aerosol particles that may act as heterogeneous ice nuclei at some point after emission. In the absence of aircraft emissions, a cirrus cloud would not have formed or the resulting cirrus would have different properties."
So, contrails was formed because the water vapor can deposit into the particle pollution emitted by the aircraft engine.