Here is some support for those who wonder and worry about the chem trails that criss cross our skies. From Tyler Durden at zerohedge.com:
A fleet of aircraft injecting sulfates into the lower stratosphere could help protect the world from climate change. Well, that is according to a peer-reviewed paper published Nov. 23 in the journal Environmental Research Letters by researchers from Harvard and Yale universities.
It sounds like rhetoric from the tinfoil-hat chemtrail conspiracy community. Large commercial airliners spraying sulfate microparticles into the stratosphere, anywhere from 8 to 30 miles high. The purpose is to help shield the Earth from sunlight to maintain lower temperatures.