A conspiracy theory holds that the condensation trails, or contrails, that are left behind by aircraft in the sky have dangerous chemicals that the government or industry deliberately but secretly spray for sinister purposes.
Believers argue that the contrails that do not dissipate quickly provide evidence of the so-called chemtrails of the additional substances.
In an international survey conducted in 2011, nearly 17 percent of the participants believe in secret largescale atmospheric program (SLAP). Some argue that the spraying is being done to offset the effects of increasing amount of atmospheric carbon dioxide and that the sprays pose health and environmental dangers as they fall to the Earth.
Now, experts debunk the chemtrail conspiracy theory. In a new study published in the Environmental Research Letters on Aug. 10, researchers surveyed atmospheric chemists who specialize in contrails and geochemists who specialize on pollution and dust that are deposited into the Earth's atmosphere, with the aim of shedding light on the suspected secret spraying program.
Of the 77 scientists surveyed, 76 said they have not encountered evidence of the covert spraying program.
"The experts we surveyed resoundingly rejected contrail photographs and test results as evidence of a large-scale atmospheric conspiracy," said study researcher Steven Davis, from the University of California Irvine.
The surveyed scientists also said that contrails are just clouds and that the alleged evidence of those who believe atmospheric spraying happens can be attributed to something else.
"The data cited as evidence could be explained through other factors, including well-understood physics and chemistry associated with aircraft contrails and atmospheric aerosols," wrote study researchers, including Ken Caldeira, from the Carnegie Institution for Science, Stanford, and colleagues.
Some also think that the trails now last longer, but experts said this could be attributed to high-flying aircraft, engines that produce more water vapor, more plane traffic, high atmospheric water vapor content due to climate change and reduced temperature of aircraft exhaust due to improved fuel efficiency.
The researchers said that the aim of the study is to provide objective science that can help in better public discussion about the issue, which could benefit those who have not yet made up their minds on whether or not to believe in this secret atmospheric spraying programs.
"Our goal is not to sway those already convinced that there is a secret, large-scale spraying program," the researchers wrote, "but rather to establish a source of objective science that can inform public discourse."
