I am looking into this myself. I was previously a criminal investigator, and I am interested in genuine conspiracies such as Snowden, and he has done an excellent job of bringing evidence into the public arena. However, the chemtrail people do not do so well.
I think it is a genuine lack of understanding of how proof is obtained, and cognitive biases such as outlined in this bookhttp://
www.amazon.co.uk/You-are-Not-So-Smart/dp/1851689397/, which I gave ordered from Amazon.
I have actually been looking into how to try and "prove" chemtrails, i.e. be the devil's advocate as it were, because I know a group of people who think they exist, and if the claim is true, then of course I want it exposed. Unfortunately, at present, the evidence they present as proof is well below adequate.
In support of chemtrails, I was presented with the Railway Children video which was debunked here
https://www.metabunk.org/threads/de...-footage-reused-in-modern-advertisement.2545/, however, like
@ChrisBovey, I saw these trails when I was younger. so this does not cut it for me, and a court would make mincemeat out of anyone bringing this television commercial as evidence.
However, it was interesting to note that there was a genuine contrail in the original 1970s film. This was just a still, but I watched it online last night, and saw a contrail at 30 minutes and 35 seconds. It is visible for about 3-4 seconds. You can see it here, behind the flock of pigeons.
I have ordered a copy of the original VHS format of this for 1p on Amazon. If the contrail is in the video, then it is good evidence. If it is not in the video, then it will provide support towards the conspiracy idea. But even if the latter, it is not conclusive proof.
The second thing I have done is ordered a secondhand copy of Clouds of the World, in an old hardback format. I am interested in this, I saw the online pictures
https://plus.google.com/photos/107393796095434664991/albums/5363662113705530081. However, these could have been altered. Best evidence is the original print, and early reprints. I don't mind buying this, I had a friend who was a meteoroligist and he explained clouds to me, they are interesting. And, my physics teacher in the 1970s explained how contrails were formed by sublimation
http://www.aviationweather.ws/027_Change_of_State.php.
In addition there is an earlier book written by the same author, available in full online
https://ia700804.us.archive.org/28/items/AColourGuideToClouds/ScorerWexler-AColourGuideToClouds.pdf. The print date is 1963. Contrails are discussed on page 44. However, this is a digital image, so - to be fair - this could have been altered too, meaning that the security ring fencing for the chemtrail conspiracy extends as far as the administrators of online libraries, as well as employees who edit television adverts.
I will wait for the book and VHS to arrive, but as I am travelling, I will not see them until December.
The point is, if the chemtrail conspiracy, however big or small, is to be taken seriously by mainstream journalists and media, it must present facts, verifiable in a court of law. So, if it turns out that the VHS and an original copy of "Clouds of the World" does show contrails, then pictorial evidence must be completely ignored, as it proves nothing. This of course will be of help to people who believe in chemtrails, because it will them make them realise that they must focus their efforts on gaining different proof.
I don't propose to spend too much time on this, I have many other things to focus on in my life. But, like
@Mick West I find these things interesting. And of course if this particular conspiracy has any truth, then the people who support it should be guided as to how to bring it out, and we should all know about it. Copying YouTube videos and poor presentation of evidence will ensure that it stays limited to the pages of David Icke and Neon Nettle.