Climate science is under scrutiny once again, this time over a modest half-a-million dollars — the collective sum of five federal and state grants being investigated by Kenneth Cuccinelli, a firebrand conservative who was elected late last year as attorney general of Virginia. The grants had multiple recipients, but the official target of the probe is Michael Mann, an internationally respected climate scientist who was an investigator on all five grants while working at the University of Virginia in Charlottesville between 1999 and 2005.

On 23 April, Cuccinelli filed what amounts to a subpoena ordering the University of Virginia to hand over, by 26 July, all available documents, computer code and data relating to Mann's research on the five grants. He also demanded all correspondence, including e-mails — from 1999 to the present — between Mann, now at Pennsylvania State University in University Park, and dozens of climate scientists worldwide, as well as some climate sceptics. The order stated that Cuccinelli was investigating Mann's possible violation of the 2002 Virginia Fraud Against Taxpayers Act — although no evidence of wrongdoing was given to explain invoking the law, which is intended to prosecute individuals who make false claims in order to access government funds.

Mann is the co-author of the famous 'hockey stick' graph, which shows estimated global temperatures over the last millennium to have been relatively constant until a drastic rise in the twentieth century. Mann has long been a target of climate-change deniers, and the scrutiny intensified last autumn when his e-mails were among those stolen from the Climatic Research Unit at the University of East Anglia, UK. But Mann's research has been upheld by the US National Academy of Sciences, and an investigation by Pennsylvania State University into the e-mails also cleared Mann of any misconduct. Given the lack of any evidence of wrongdoing, it's hard to see Cuccinelli's subpoena — and similar threats of legal action against climate scientists in a February report by climate-change denier Senator James Inhofe (Republican, Oklahoma) — as anything more than an idealogically motivated inquisition that harasses and intimidates climate scientists.

Certainly Cuccinelli has lost no time in burnishing his credentials with far-right 'Tea Party' activists, many of whom hail him as a hero. In March, he instructed Virginia's state university presidents that they had no legal authority to protect homosexuals under their non-discrimination policies. He has also filed lawsuits challenging health-care reform and the Environmental Protection Agency's authority to issue greenhouse-gas regulations.

Cuccinelli's actions against Mann hark back to an era when tobacco companies smeared researchers as part of a sophisticated public relations strategy to raise doubts over the science showing that tobacco caused cancer, and delayed the introduction of smoking curbs for decades. Researchers found themselves bogged down in responding to subpoenas and legal challenges, which deterred others from the field. Climate-change deniers have adopted similar strategies with alacrity and, unfortunately, considerable success.

Cuccinelli has insisted that he is not “targeting scientific conclusions”. But even several climate sceptics who count themselves among Mann's fiercest critics have publicly condemned the attorney general's move. Thankfully, so have many academic bodies. One of them was the University of Virginia's faculty senate, which on 5 May declared that Cuccinelli's “action and the potential threat of legal prosecution of scientific endeavor that has satisfied peer-review standards send a chilling message to scientists engaged in basic research involving Earth's climate and indeed to scholars in any discipline.”

Well said. Scientific organizations must respond quickly and forcefully any time political machinations threaten to undercut academic freedom. And, rather than complying, the University of Virginia should explore every avenue to challenge the subpoena.