It's an indictment that the research even needed to be done, but a study of scientists in the most relevant fields has found even less support for “chemtrail” conspiracy theories than exists for climate change denial. Sadly the paper is unlikely to change many minds.
Airplane exhaust gasses sometimes produce a white trail, known as a condensation trail, or contrail, and how long these remain visible depends on weather conditions. Photographs have recorded long-lasting contrails since the 1940s, with eyewitness accounts from earlier still, but in recent years some people have become convinced that persistent contrails contain more than water. Instead, they are alleged to be proof of a “secret large-scale atmospheric program” (SLAP), a vast conspiracy to drug the population into submission, change the climate, or both.
A 2011 international survey found that 2.6 percent of those asked considered SLAP claims “completely true” and 14 percent thought them “partly true”.
To see if there was any support for the idea that governments are deliberately fouling the air with chemicals spat out the back of airplanes, Dr Steven Davis of the University of California, Irvine, contacted 77 scientists, presenting them with claims made by SLAP proponents, such as photographs of purported chemtrails and metals found in ponds and snow under flight paths.
Davis chose atmospheric scientists who would understand the way condensation trails evaporate and environmental chemists familiar with metal concentrations and laboratory testing. Seventy-six of those approached responded that non-SLAP related explanations were not only possible, but more plausible than the alternative. The one exception represents 1.3 percent, less than the 2-3 percent of scientists who dispute human responsibility for global warming.
"The experts we surveyed resoundingly rejected contrail photographs and test results as evidence of a large-scale atmospheric conspiracy,” Davis said in a statement.
Davis and his co-authors published their findings in Environmental Research Letters, but ruefully acknowledge they are unlikely to sway chemtrail believers. “Our goal is not to sway those already convinced that there is a secret, large-scale spraying program – who often reject counter-evidence as further proof of their theories – but rather to establish a source of objective science that can inform public discourse,” they write.
Rationally speaking, a SLAP is a particularly improbable theory. Spraying chemicals from a great height is an exceptionally inefficient way to get chemicals to targets. If the plan really was to control people's minds, reduce our fertility or cull the old, spraying chemicals on busy airline routes would be possibly the most unreliable method imaginable to achieve it.
The very modest effects of rain-seeding programs, designed to achieve a tiny form of geoengineering, reveals how impractical a global effort would be, even if governments and airlines could reach agreement on their goals. Moreover, chemtrail enthusiasts will apparently believe anything that encourages them to worry.
As the paper notes: “There have been no peer-reviewed studies in the scientific literature addressing SLAP claims,” probably because most scientists consider them too improbable to even address. Noting the extent of the belief's spread the authors thought it time to check scientific opinion.