On April 6 and 15, the temperature in Paris suddenly rose about three and a half degrees within a few minutes. At least, that is what the weather station at Charles de Gaulle airport reported, a data source used by the Polymarket forecast market to settle bets on the Parisian weather. Anonymous user ‘xX25Xx’ bet on both days that the temperature would rise above eighteen degrees, winning a total of $34,000. The French police are investigating whether the measuring equipment has been tampered with.
The suspicious temperature increases were spotted by meteorologist Ruben Hallali, who also discovered on April 15 that a Polymarket user was making predictions that exactly matched the spiking temperatures. No weather station in the area showed the same increases, and the measurements could not be explained meteorologically. Shortly after the report, the user deleted his account.
On internet forums such as Discord, users of the gambling platform speculate about the precise method of influence. A lighter or a hairdryer near the temperature sensor seems most likely, although the police have not yet completed the investigation. Météo-France does not comment on possible causes.
Hallali warns about the ubiquity of prediction markets like Polymarket. The sensors on which such platforms are based are difficult to protect against tampering, he writes on LinkedIn. “Fraud of $34,000 is a novelty, but the real problem remains underexposed.”
You can bet on more things than the weather via Polymarket. Users placed millions of dollars in bets on, for example, the outcomes of sports matches, the possible dismissal of American TV presenter Jimmy Kimmel and geopolitical events such as the reopening of the Strait of Hormuz.
Prediction markets use wisdom of crowds: the idea that people, although they do not make good predictions individually, in large groups they are on average close to the correct answer. A success story is the Iowa Electronic Markets, a small-scale market set up for research purposes. This turned out to predict Barack Obama’s election win in 2008 more accurately than regular polls.
Data manipulation and insider betting on Polymarket have become more common lately. For example, an American soldier was recently arrested for plotting the departure of Venezuelan President Nicolás Maduro, shortly before his kidnapping became known. He is said to have earned about $400,000.
