Photo: Jeff Kubina (Flickr)

Solar geoengineering is controversial, and for good reason. It describes a set of technologies that seeks to reflect a small fraction of sunlight back into space to cool the planet. The most prominent such technology involves deliberately injecting tiny reflective particles into the stratosphere.

There’s a serious debate worth having, both on the science and technology itself and on the societal and policy implications. Unfortunately, in some corners of society valid concerns over the impacts of solar engineering have been overtaken by a different set of fears—various versions of the so-called chemtrails conspiracy theory.

According to that conspiracy, solar geoengineering has been happening at scale for years or even decades.

The conspiracy isn’t exactly small. Around 60 percent of all social media discourse on geoengineering is conspiratorial, according to co-authored research I published last year. A representative poll of the U.S. public reveals that 10 percent describe the conspiracy as “completely true,” another 20 to 30 percent say it is “somewhat true.” Belief in the conspiracy appears across party lines, and it can get rather personal, too—death threats and all.

Most versions of the conspiracy involve planes crisscrossing the skies spraying toxins, turning ordinary contrails into “chemtrails.” Motivations range from weather modification (and yes, there are serious research efforts on that topic, too) to mind control or worse. No surprise, Twitter and other largely anonymous online fora allow this community of conspiracy to flourish—necessitating responses showing that no, NASA does not have a “cloud machine” but is instead testing its rocket boosters.

Advertisement

I have no doubt that some who have stumbled upon the chemtrails conspiracy are earnestly looking for the truth. Much like some who believe that vaccinations cause autism, despite all evidence to the contrary, are motivated by having a close relative suffer from autism, chemtrail conspirators sometimes appear to be looking to learn why a loved one suffers from a respiratory illness. The real answer, sadly often, is indeed air pollution, which kills some 3 to 6 million people a year globally. Decreasing that pollution clearly ought to be a global priority.

It is also clear that some of those peddling the conspiracy do so for mercenary reasons—selling ads on their website, or using it to grow their brand and drive page clicks.

Whatever the motivation, the “evidence” presented in favor of the conspiracy does not add up. Conspirators often argue that all one needs to do is look up. Scientists have. What they see are contrails: trails largely made up of condensed water vapor. It is the same effect that occurs when you breathe out on a cold day. If the air is sufficiently cold and moist, a plane’s mere turbulence can cause a contrail to form. Adding exhaust from a jet engine aids the process.

Advertisement

Contrails have been with us since the dawn of aviation. The earliest explanation of the science I could find in the popular press is a March 1943 article in Popular Science explaining what was then called “vapor trails.”

The number of contrails, of course, has since increased dramatically, in line with the number of planes in the sky. And yes, those planes pollute. Each roundtrip flight from New York to San Francisco emits around 1 ton of CO2 per economy-class passenger. Sadly, CO2 is invisible. Were it a smelly pink goo, the world would have acted much sooner on CO2 pollution. It hasn’t, despite amazing progress slashing other kinds of air pollution.

In fact, some of the progress reining in air pollution, such as the sulfur dioxide (SO2) coming out of smoke stacks, leads to serious climate tradeoffs. While outdoor air pollution kills, it also—inadvertently—counteracts some of the warming effects of CO2. Removing all such air pollution, while clearly positive for human health, could indirectly cause a lot of harm, as the planet warms even further. The result is what Nobel Prize-winning chemist Paul Crutzen, in 2006, described as a “Catch-22.”

Advertisement

It is also, to me personally, the best moral case for solar geoengineering research in the first place.

This is precisely where the real solar geoengineering debate ought to be had. What are its potential risks and benefits? Would mere talk of solar geoengineering distract from the need to cut CO2 emissions? Or would such talk be a clarion call to prompt more action on climate mitigation? Reasonable people can disagree and, ultimately, can come down on different sides of the question of whether solar geoengineering could—or should—play a role in an overall climate policy portfolio.

But these arguments are a far cry from claims that contrails are really “chemtrails,” that thousands of commercial planes aren’t “merely” emitting massive amounts of CO2 but, for example, are deliberately spraying alumina. Aluminum oxide, in one’s soil, is presented as “evidence” for chemtrails. It isn’t. Aluminum is the third-most abundant element in the Earth’s crust, and aluminum oxide is its most common form. Other supposed explanations are even odder and wholly unbelievable to scientists having looked at the topic.

Advertisement

All that, of course, raises the question of why to trust scientists in the first place. Wouldn’t they have an incentive to hide evidence if there were a global “chemtrails” program operating somewhere? Well, no—that’s just not how science works. Does any one institution have incentives to keep secrets? Sure. But would individual scientists across the world keep some sort of vast “chemtrails” conspiracy a secret?

Scientists aren’t all that good at lots of things. Polite, social interactions might be one. But the one thing they are good at is pointing out why others are wrong, and improving on prior knowledge. Pointing out why the broad scientific consensus that the planet is warming and humans are the cause of it is wrong would clearly make a scientific career. The fact that this hasn’t happened makes me comfortable to trust the consensus science on climate change. The fact that in decades no scientist has shown that ordinary contrails aren’t just that makes me similarly confident that there isn’t anything to the “chemtrails” conspiracy.

The world faces a serious pollution challenge. That goes for SO2 killing scores today, and it goes for the impacts of CO2 both today and in the future. There are some serious tradeoffs between the two. That’s the debate to have, and anyone I know who does research on solar geoengineering is happy to have it. It’s also the kind of debate that anyone with an earnest interest in the future of our planet should want to participate in.

Advertisement

Gernot Wagner is research associate and lecturer at Harvard, co-director of Harvard’s Solar Geoengineering Research Program, and co-author of Climate Shock.