Conspiracy theories about weather manipulation go back centuries and are more dangerous than you might think.

In the ninth century, St Agobard of Lyon wrote a treatise called On Hail and Thunder attacking the popular superstition that storm-raisers could call up tempests at will. Bizarrely, these magicians were supposedly paid by aerial sailors from the land of Magonia, who sailed in the clouds and collected the crops destroyed by hail and storms.

Agobard relied mainly on biblical authority, citing passages indicating that only divine power could control the weather. But he also used logic, asking sarcastically why supposed storm-raisers did not slay their enemies with giant hailstones, or offer to end droughts with rain showers.

Belief in storm-raising persisted. King James I (James VI of Scotland) had dozens of supposed witches arrested, tortured and probably executed for calling up the storm that nearly wrecked his ship when he sailed home from Scandinavia in 1590.

Such ignorance might now seem absurd. But several US states, motivated by conspiracy theories about government-created hurricanes and other weather disasters, are moving to criminalise atmospheric experiments. Last year Tennessee was the first to pass a law banning cloud seeding. Such laws could prevent legitimate meteorological research, as well as feeding paranoia about chemtrails and other threats that are as imaginary as storm-raising.