Climate scientists with the National Oceanic and Atmospheric Administration (NOAA) have been cleared of data manipulation and other unethical behaviour after a lengthy investigation.

Following the leak in November 2009 of climate science-related emails from a server at the University of East Anglia in the UK, leading NOAA researchers were accused of having been involved in an alleged attempt to play up the threat of global warming.

“In our view, the CRU documents and emails reveal, among other things, unethical and potentially illegal behaviour by some of the world’s pre-eminent climate scientists,” US Senator James Inhofe (Republican, Oklahoma) wrote in a report to the US Senate released last February. The report implied that criminal prosecution could be forthcoming against several scientists involved in the ‘Climategate’ affair, including prominent NOAA researchers Susan Solomon and David Karl.

Those implications have now been thoroughly refuted. The inspector general of the US Commerce Department, which oversees NOAA, has found no evidence in the leaked emails of any wrong doing. Its report, released yesterday, concludes that there is no reason to doubt NOAA’s handling of climate data. The report does, however, criticise the way NOAA handled several Freedom of Information Act request in 2007.

“We welcome the Inspector General’s report, which is the latest independent analysis to clear climate scientists of allegations of mishandling of climate information,” said Mary Glackin, NOAA’s deputy under-secretary for operations. “None of the investigations have found any evidence to question the ethics of our scientists or raise doubts about NOAA’s understanding of climate change science.”

Previous inquiries in the US and in the UK have cleared other prominent scientists involved in the affair of scientific misconduct.