evidence: 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. [...] 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. [...] 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?