What evidence is there that these are not condensation trails?

 http://en.wikipedia.org/wiki/Chemtrails

The obvious difference between chem trails and contrails:

CHEM trails hang in the sky all day,are arranged in a grid system and do exist.

CONtrails dissapate in half an hour.

Anyone who still thinks chemtrails are for looneys should research cloud seeding and weather modification.Governments have been doing this for decades.

Anyone who says otherwise is scared and conditioned.

 http://www.weatherwars.info/index.php

 http://www.globalresearch.ca/articles/WOR406A.html

"Anyone who still thinks chemtrails are for looneys should research cloud seeding and weather modification. Governments have been doing this for decades. Anyone who says otherwise is scared and conditioned. "

Everyone who has seen a crop-duster or coloured smoke display as seen a chem-trail. Whether commerical aircraft are used for cloud seeding and weather modification is a different matter and would require much more proof than that video.

Ordinary contrails effect on global-dimming and global-warming is certainly interesting. When the planes didn't fly after 911 the diurnal temperature increased. According to this article, night-flights should be banned.  http://www.scienceagogo.com/news/contrail_controversy.shtml
It also says the B2 bomber doesn't produce contrails and that the same technology could be applied to commercial-aircraft to stop contrail effects on the environment.

Just because a subject isn't looney doesn't stop the looneys expressing an interest though. dense.com puts it down to either being to create traffic corridors for transparent UFOs to fly around unobserved OR the iIlumminati world government dosing us with GM modified viruses.

" The obvious difference between chem trails and contrails:

CHEM trails hang in the sky all day,are arranged in a grid system and do exist.

CONtrails dissapate in half an hour."

This is farcical. What's that, EXACTLY half an hour? Who says?

It's really VERY simple. Upper atmosphere humidity VARIES from day to day. Some days when the Relative Humidity is low up there, the contrails which contain, wait for it - water vapour - will dissipate in a short time as the condensed visible water droplets or ice particles re-evaporate into invisible water vapour as they mix with the drier surrounding air - like a kettle in a dry room. Other days when the RH is high or maybe even supersaturated the trails will act as a nucleus for water vapour already in the air that will then condense out over a larger area into visible water droplets or ice particles. See, no knee jerking conspiracy needed at all.

Pedantic but your title was misleading and I've a few questions if you have any pretensions of science. I don't but I am curious.
Do you believe 'plasma aerodynamics' could end contrails if the USAF shared it's technology with commercial airlines as it alleged in my link and what are the implications of that if it is true. Do you believe the reported temperature rise when 911 grounded jets was at least part due to contrails ?

Seeding jets contrails with particulates at certain altitudes to offset global warming isn't science-fiction. Would there be a way to make a contrail last longer if you wanted to ? How would an ordinary water-vapour contrail do if it was seeded by silver iodide ?
There might be an argument for doing so, although any potential and dubious gain would not offset the climate damage airliners do, but if the airliners were flying anyway...
States have been accused of 'stealing each others rain'. After all, there is only so much precipitation and evaporation, cloud-seeding must be regional like damming another countries rivers. How are those processes affected by global-warming ? Do all the particulates they use such as silver iodide return to earth as precipitation quickly or do they remain in the upper-atmosphere for some time ? And if so, could regional climate policy (ie cloud seeding) be adversely affecting the global climate ?

You're all very stupid

This photo lifted from Paul T's unconvincing site proves my above point perfectly. There are loads of lasting contrails all over the country where there is already thin hazy cloud, ie: the RH there is high. But in the band stretching across from the Severn estuary to East Anglia there are no lasting contrails there because there is no cloud in that band, ie: the RH there is low. Or do you really think that all the pilots agreed together to switch off the toxic chemical mind control sprayers just as they flew over that band and then on again at the other side maybe because...
um...
because they all know various people who are at simultaneous weddings in that band? Yes that's got to be it!