We had some crisp fall weather a few days ago, and while bird watching, I noted a large number of jet contrails coming from the east as the afternoon flights from Europe arrived over the U.S., destined for New York, Chicago and other major airports.  Most of these left well-defined contrails, which are plumes of water vapor from the combustion of jet fuel at high altitudes. When the hot exhaust hits the cold air of the stratosphere, it condenses to form clouds or ice crystals. Stratospheric winds disperse the contrails as the jet moves on, so they appear to spread widely across the sky. Then, slowly the condensed water goes back into vapor and the contrails disappear, much as fog disappears when the morning sun warms the air.

Contrails only form on days when the stratosphere is very cold. Our knowledge of the formation, persistence and effects of contrails is so refined that they are routinely included in models of global climate, where they don’t have much effect. See

In my evening perusal of our local community bulletin board on Facebook, I found a collection of entries about the afternoon’s chemtrails—how they were interspersed with contrails to mask their presence and how many appeared to be generated over Canada. 

No myth persists more strongly than the conspiracy theory associated with chemtrails.  As the theory goes, chemtrails are composed of fine chemical particles dispersed in covert operations by the military or other government agencies to control our behavior or the climate.  Advocates of chemtrails believe that chemtrails are interspersed with jet contrails high in the atmosphere, but recognizable by their unusual color and persistence. In one recent survey, some 17% of people interviewed believed in the existence of chemtrails. 

Problem is: there is no credible evidence that chemtrails exist. 

Convincing evidence would come from the identification of unusual chemical substances in rainfall or dry fallout from the atmosphere—chemicals like barium, aluminum, lithium, sulfate, silver, or any of a wide variety of pharmaceuticals that might alter human behavior. No one has ever found any of these substances in rainfall that could be linked to dispersal by high-flying aircraft.

In traditional debate, the protagonists bear the burden of proof—here, the proof of chemtrails.  The antagonists merely have to show that the proof is incorrect.  Somehow, with chemtrails, we have it backwards.  No proof of chemtrails has ever been published but the protagonists believe that any arguments counter to the existence of chemtrails stem from attempts to cover-up their existence.

And that is how alternative facts are generated.



Shearer, C., M. West, K. Caldeira and S.J. Davis. 2016.  Quantifying expert consensus against the existence of a secret, large-scale atmospheric spraying program.    Hide ResearcherID and ORCIDEEnvironmental  Environmental Research Letters 11:  doi:10.1088/1748-9326/11/8/084011