Jet condensation trails, or contrails, have spawned wild conspiracy theories alleging mind control and the spreading of disease, but scientists say the real problem is their warming effect.

Researchers argue these smoky trails essentially double the amount of heating that’s caused by aviation’s use of fossil fuels.

The problem will be discussed at the UN climate conference, COP29, in Baku for the first time.

Contrails form in the sky in the same way that your breath goes misty on a chilly morning.

When a plane passes through cold humid air, the contrails form as the vapour from the engines condenses on unburned fuel fragments in the exhaust stream.

While the causes of contrails have been known about for decades, it’s only in recent years that the climate warming impact of these human generated clouds has been recognised.

“They create an artificial layer of clouds, which traps the heat from the Earth that’s trying to escape to outer space,” said Carlos Lopez de la Osa, from the Transport & Environment campaign group, which has carried out a new study on the solutions to contrails.

“The scale of the warming that’s associated with them is roughly having a similar impact to that of aviation carbon emissions.”

Conspiracy theories have grown up around contrails, with some people alleging they are in fact “chemtrails” that contain chemical or biological substances.

The aim of these chemtrails is either vaccinating the population, spreading pandemics or controlling the minds of the masses, the conspiracy theories go on to claim.

All of these ideas are completely untrue.

“It is unfortunate that these conspiracy theories are muddying the water on an issue where we need a lot of consensus, a lot of clarity,” said Matteo Mirolo, from Breakthrough Energy, and one of the organisers of the COP29 discussion about the contrails.

“Chemtrails are an unfounded theory. There’s simply no scientific backing.”