Protestors demonstrate outside the US Supreme Court on 5 October, as justices hear a case for which the outcome could determine whether fossil-fuel companies can be held responsible for global warming. Credit: Mehmet Eser/Anadolu via Getty

Last month, a climate scientist working in the University of California system received an unsettling message from her institution. University officials asked her to submit all correspondence related to a study she had published linking emissions from fossil fuels to environmental harms caused by climate change. The university had received a public-records request from a law firm representing the Patriots Foundation in Des Moines, Iowa, which describes itself on its website as a government watchdog.

It was the fifth such request connected to the organization that the scientist, who requested anonymity to avoid further demands, had received this year.

Heatwaves linked to carbon emissions from specific companies

The requests seem to be part of an expanding effort by…