This story was originally published by the Guardian and is reproduced here as part of the Climate Desk collaboration. A conspiracy theory that airplanes are leaving nefarious “chemtrails” in their wake due to a sinister government plot has been given fresh impetus in the US amid a swirl of concerns and confusion about proposals to geoengineer a response to the climate crisis. State legislation to ban what some lawmakers call chemtrails has been pushed forward in Tennessee and, most recently, Florida.