Government conspiracy…or just jet contrails?

(Photo by Fernando Kokubun)

(Photo by Fernando Kokubun)

In one of the newspapers in which Almanac Weekly appears, the same letter-writers offer repeated excursions into sinister conspiracy and pseudoscience. The theme is always the same: An evil “they” are deliberately harming us.

These diatribes range from how a renegade “cabal” of the US military murdered us on 9/11 to Wi-Fi making schoolchildren sick to how the supposed hazards of cell phones are well known to governments, corporations and even health organizations like the Mayo Clinic, but they’re all “in on” the plot.

Recently the delusions have shifted to “chemtrails.” According to this particular conspiracy, the government continually sprays us with chemicals that we can actually see as spreading white substances behind jets. I cringe not just because this shows an amazing ignorance of basic science, but also because such notions could make people unduly cynical about our country – and there really are many good, idealistic people in office, from the president on down. So here’s the true story.

A jet doesn’t leave a white trail when it takes off, nor when it’s flying low. But when it climbs high into very cold air, the story changes.

Jets burn kerosene. If you’ve ever used a kerosene heater or lamp, you’ve smelled the exhaust products. These include water vapor, bits of carbon soot, some carbon compounds like methane and trace amounts of impurities like metals. Well, when jets climb above 30,000 feet, the air is so cold at -40 degrees that the exhaust’s water vapor instantly freezes into ice crystals. This is a contrail, a short white line behind the engines. It often dissipates in seconds, as each crystal sublimates back to invisible vapor.

Jets often zoom through such cold air, and it can take a long time for the contrail ice to vaporize. Higher humidity preserves it, too. The contrail then lingers as a long white line across the entire sky. Winds typically distort these into various curves. If the airmass is very humid, the exhaust’s soot particles enter the picture to act as condensation nuclei – like cloud seeding – to produce a thicker contrail as surrounding atmospheric vapor freezes as well. The ice crystal formation spreads out. Rarely, in very high humidity, the contrail can act as the “starter yogurt” for a cloud covering the sky.

People into meteorology and aeronautics have observed and photographed all these various contrail varieties since the 1930s. Contrail science is even taught in college courses. Experts can assess the temperature, humidity and winds at various altitudes simply by observing them.

These artificial pencil clouds reflect sunlight into space. A few years ago scientists were concerned that jet traffic would therefore have a cooling effect on the planet. But global warming has made that issue go away.

The folks who regard contrails suspiciously obviously don’t know what they are. Several websites call the lines chemtrails and claim that the US military is deliberately spraying a substance upon the population – an idea that meteorologists generally find hilarious.

I’ll explain why it’s so silly. First, if you’ve ever watched crop-dusting, or seen the unfortunate videos of Agent Orange being sprayed during the Vietnam War, you know that chemicals must always be released very close to the ground – preferably treetop-level. If released high up, they’d dissipate and take forever to get down, with an ultimate soil concentration of essentially zero.

Second, my commercial pilot friends (along with the controllers at the Federal Aviation Administration) would all have to go along with the plot, since they’d see the process happening. I’m a pilot and airplane-owner myself; it’s not happening.

Third, what would be the purpose? Some say mind control. But are people acting differently lately? Others say that it’s to sow disease, and some even claim to be the only people to know what causes autism: It’s chemtrails! But why would anyone want to do this?

Some say that “chemtrails” are a government project to combat global warming. Nice, but then why should such a laudable and expensive effort be kept hush-hush? And how on Earth would thousands of blabbermouth pilots keep such a secret? Other Web-based “explanations” involve similarly wacky stuff like “electromagnetic rays.”

Finally, I’ve observed these same spreading-out contrails from more than 40 countries during five years overseas, including from Russia and the Falkland Islands. If it’s a secret government thing, everyone else is doing it too – and long before global warming was even known to exist.

Logic never placates the paranoid. They claim that soil tests show dangerous substances in the soil everywhere, and their websites offer chemtrail videos. But even amateur weather-watchers readily recognize these as contrail phenomena observed since before the Second World War: no mystery, and nothing sinister at all.

Those spreading this scare nonsense act as if they’re Paul Reveres sounding the alarm. Their motives are probably noble. But anyone who has concerns should just phone their alma mater and get a callback from an academic meteorologist. Talk to a college department head. Or contact a radio station’s weatherperson. Ask an expert whether any airplane exhausts have ever looked remotely suspicious.

We’ve got enough challenges without getting distracted by make-believe.


Want to know more? To read Bob’s previous “Night Sky” columns, visit our Almanac Weekly website at

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