Published July 18th 2012: "A challenge to Chemtrail Believers - Explain this 1969 Issue of Popular Science:
Chemtrail believers claim that persistent contrails are a new thing, and they call them chemtrails. They also claims that contrails don't last a long time, and they certainly don't spread out and cause cirrus clouds and overcast skies. They also claim the chemtrails started in the late 1990s.
And yet, here's an issue of Popular Science, from 1969, 43 years ago, which says:
'How Jet Planes affect weather
The reflectivity of the earth is also altered by jet contrails, say Dr. Walter Orr Roberts, director of the National Center for Atmospheric Research.
Contrails, Dr. Roberts explains, do not simply spread out at the 30-40,000-foot altitudes where jets fly, but spawn cirrus clouds by seeding the upper atmosphere with ice crystals from the water vapor in jet exhaust. On a clear day, you can often see this happening near heavily traveled airways.
'It is almost certain that on many occasions - 30 to 40 days a year, say - the cause of cirrus cloud cover can take in a substantial part of a continent, perhaps half of the U.S., and has a substantial influence on our radiation budget'
- Popular Science, May 1969, Page 76'
So what's going on? If contrails have always done this, then why are some people insisting they did not? Are they just mistaken, or deliberately misleading people?"
