Discussion

I guess I have to make the tough choice between ignorantly sitting in front of my computer, blissfully unaware of all of the secret plots to kill me, versus ignorantly disregarding all intelligent science and solid evidence, so that I can live a life of paranoia and fear...

It's a tough choice... but I think I'll go with... those that laugh at Chicken Little!

Don't sweat it Wild woman, They are just spraying to kill the bark beetles, they do it all the time and its not too toxic to normal people unless you have an algery to diuxbcivntcbvion then you may be in trouble. I am wondering why the trails went all over the Inland Empire yesterday as far as the eye can see. Do they have bark beetles down there too?

This is from Wickipedia and goes along with cynthia1957 said,

Contrails or vapor trails are condensation trails and artificial cirrus clouds made by the exhaust of aircraft engines or wingtip vortices which precipitate a stream of tiny ice crystals in moist, frigid upper air. Being composed of water, the visible white streams are not, in and of themselves, air pollution. However, vapour trails or contrails generated by engine exhaust are inevitably linked with typical fuel combustion pollutants.

[edit] Condensation from engine exhaust
The main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can push the water content of the air past saturation point. The vapor then condenses into tiny water droplets and/or deposits into ice particles . These millions of tiny water droplets and/or ice crystals form the vapour trail or contrails. The energy drop (and therefore, time and distance) the vapor needs to condense accounts for the contrail forming some way behind the aircraft's engines. The majority of the cloud content comes from water trapped in the surrounding air.[citation needed] At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly turn to ice crystals. Exhaust vapour trails or contrails usually occur at above 26,000 feet. where the temperature is below -40°C (-40°F).[1]

[edit] Condensation from decreases in pressure
Main article: wingtip vortices
The wings of an aircraft cause a drop in air pressure in the vicinity of the wing. This brings with it a drop in temperature, which can cause water to condense out of the air and form a vapour trail or contrail. This effect (the Prandtl-Glauert singularity), is more common on humid days, and can be seen on fighter jets performing high energy maneuvers, during shuttle launches, on the expanding surface "bubble" of nuclear explosions, or on airliners during takeoff and landing. Additionally, the area around a turbo-fan intake will be at a lower pressure than the surrounding air, and may result in a condensation fog forming there during high power settings.

These effects are compounded with the other explanation of contrails, which is the water vapor produced by the combustion of jet fuel. High altitude contrails are seen directly behind the one or two jets, and with aircraft with four jets, such as the Boeing 747, there are four contrails. The vapor trails caused by the first mentioned effect are usually seen at low altitude where the ambient humidity is higher, and they follow the wings rather that the jet engines.

[edit] Vapour trails or contrails and climate
Vapour trails or contrails, by affecting the Earth's radiation balance, act as a radiative forcing. Studies have found that vapour trails or contrails trap outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) at a greater rate than they reflect incoming solar radiation (negative radiative forcing). Therefore, the overall net effect of contrails is positive, i.e. a warming.[2] However, the effect varies daily and annually, and overall the magnitude of the forcing is not well known: globally (for 1992 air traffic conditions), values range from 3.5 mW/m² to 17 mW/m². Other studies have determined that night flights are most responsible for the warming effect: while accounting for only 25% of daily air traffic, they contribute 60 to 80% of contrail radiative forcing. Similarly, winter flights account for only 22% of annual air traffic, but contribute half of the annual mean radiative forcing.[3]

[edit] September 11, 2001 climate impact study
It had been hypothesized that contrails may affect the weather, reducing solar heating during the day and radiation of heat during the night by increasing the albedo. The suspension of air travel for three days in the United States after September 11, 2001 provided an opportunity to test this hypothesis. Measurements did show that without contrails the local diurnal temperature range (difference of day and night temperatures) was about 1 degree Celsius higher than immediately before;[4] however, it has also been suggested that this was due to unusually clear weather during the period.[5]

Then there is this....I hear the black helicopters coming! There is a whole movement of people out there who believe this, There are magizines and web sites galore! I'm not suprised....

AEROSOL OPERATION
CRIMES & COVER-UP
http://www.carnicom.com/contrails.htm

Look up and See the Pollution Raining Down on You!
http://www.apfn.org/apfn/contrails.htm

What do you make of this Mulder? Scully! You turning green from that Chem-trail raining on you! Could this be the cause of Global Warming? The Truth is out there!