Chemtrails Can't Be Proven, Say Top Scientists — But Will That Sway Believers?

The atmospheric phenomenon left behind airplanes are called contrails, and have become fodder for conspiracy theorists. Bert Modderman/Getty Images

At some point, you've probably looked up into the sky and noticed those odd line-shaped clouds that are left behind after a jet aircraft has flown over. Those white streaks are condensation trails, or contrails, and they formed when jet engine exhaust—which contains carbon dioxide and other gases, water vapor, and soot and metal particles—comes into contact with cool moisture in the atmosphere, which forms water droplets that then freeze and turn into ice particles. Sounds fairly innocuous, huh?

But in the minds of Internet conspiracy theorists, they're anything but harmless. To them, the streaks are "chemtrails," which they claim that are evidence of some secret government conspiracy to control the weather, the minds of the population, or perhaps to conduct biological warfare.


"North America is now suffering its seventh year of conspicuous and dangerous aerosol and electromagnetic operations conducted by the U.S. government under the guise of national security," warns a 2013 article on one such website, GeoEngineering Watch. "Concerned citizens watch in fear as military tankers discolor the skies with toxic chemicals that morph into synthetic clouds."

It might like a storyline from "The X-Files," but you might be surprised how many people think it could be happening. In a 2013 Public Policy Polling survey, five percent of Americans said they believed that those streaks in the sky are chemicals sprayed by the government "for sinister reasons," while another eight percent weren't completely ruling it out.

But don't order that hazmat suit just yet. In a survey just published in the journal Environmental Research Letters, a group of scientists who study the atmosphere and pollutants were asked to evaluate the evidence of a secret spraying program the conspiracy websites offer, such as photos of the streaks left behind by aircraft and analyses of soil, water and snow in remote areas for strontium and other scary-sounding substances

The result is not going to make conspiracy buffs happy. Of the 77 scientists surveyed, 76 said they had seen no evidence in their work of a secret large-scale atmospheric program — or SLAP, as some call it. They concluded that the conspiracy theorists' supposed proof could be explained in other ways, often by well-understood principles of physics and chemistry. Check out this HowStuffWorks Now video as our host Jonathan Strickland explains the findings:

"The chemtrails conspiracy theory maps pretty closely to the origin and growth of the internet, where you can still find a number of websites that promote this particular brand of pseudoscience," study co-author Steven Davis, University of California, Irvine associate professor of Earth system science, said in a UCI press release. "Our survey found little agreement in the scientific community with claims that the government, the military, airlines and others are colluding in a widespread, nefarious program to poison the planet from the skies."

But what about the one scientist who claimed to have seen evidence of chemtrails? As the study explains, that lone researcher — who wasn't identified — had come across high levels of atmospheric barium in a remote area where the soil normally would be low in the element.

Study co-author Mick West — a computer and software engineer who maintains the conspiracy theory-debunking website — isn't surprised that the lone dissent exists. "If you take any group, there's a small percentage of outliers," he says. "Two or three percent of climate scientists don't believe that humans are causing global warming."

Other atmospheric researchers would offer alternative explanations for the barium, he says. But when it comes to the photos, West pointed out, the scientists were 100 percent in agreement that they didn't provide any proof of a spraying program.

West thinks it's important for scientists to actively challenge the chemtrails conspiracy theory, which he thinks distracts the public from real environmental problems, such as the need to curb carbon emissions. But he's not confident that the researchers will win over the hardcore believers, who are likely to simply view the study as government-backed propaganda being disseminated to cover up the plot.

Skeptic magazine founder and Scientific American columnist Michael Shermer, who has written extensively about pseudoscience and conspiracy theories, agrees with West. He writes vie email that he expects the study will persuade "only those on the fence, who have perhaps heard of chemtrails but don't know much about them, or are vaguely aware of the conspiracy theory but haven't thought much about it. To skeptics it will confirm what we already know — it's just contrails — but to the true believer, there is no evidence that could ever disconfirm the conspiracy theory. That is the power of belief."

Here's a little more background on chemtrails thanks to our Stuff They Don't Want You to Know colleagues: