evidence: Though the theory may sound far-fetched to some, chemtrails have become a common conspiracy both in the U.S. and around the world, despite evidence to the contrary. What is the chemtrails conspiracy theory? The chemtrails idea has been around since 1996, and is largely rooted in an Air Force research paper from the same year, "Weather as a Force Multiplier: Owning the weather in 2025." It outlines a "future weather modification system to achieve military objectives" using "aerospace forces," and "does not reflect current military policy, practice, or capability," the Environmental Protection Agency has stated.