The National Science Foundation has closed its investigation into Pennsylvania State University climatologist Michael Mann after finding no evidence of scientific misconduct related to his research.

It is the latest in a string of investigations to exonerate scientists involved in the so-called "Climategate" email scandal.

Mann was a central figure in the fracas, where a sampling of correspondence from climate scientists purloined from a computer server at the University of East Anglia in Britain supposedly showed climate scientists colluding to fabricate data and smear critics.

But a successive series of investigations and inquiries since the emails were released in 2009 have exonerated the scientists. The final conclusion from the NSF's Office of Inspector General is no different.

"No direct evidence has been presented that indicates the subject fabricated the raw data he used for his research or falsified his results," the report concludes. "Lacking any direct evidence of research misconduct, ... we are closing this investigation with no further action."

The NSF released its conclusions last week and, following standard protocol for investigations, did not mention Mann by name. "We do not identify the subject by name due to privacy considerations," said Susan Carnohan, chief of staff to the inspector general.

Mann, in an interview, said he had received a letter from the inspector general about the case that referenced the same case number identified in the NSF's closeout memorandum.

And several other clues in the memo point to Mann, particularly a reference to a university inquiry into four allegations of research misconduct – the same four allegations investigated, and subsequently dismissed, by Penn State.

The NSF audit doesn't put the email scandal completely behind the scientists. A separate case, by Virginia Attorney General Kenneth Cuccinelli to obtain emails from when Mann was a professor at the University of Virginia, remains in court but was rebuffed last year by a state judge who found no evidence of fraud.

But it does "completely vindicate" climate scientists, said liberal blogger Joe Romm, who first broke the story on his website, Climate Progress, and who lamented the lack of attention the investigations have received compared to the uproar accompanying their release two years ago.

"The vindications of the science and the man are reported as quietly as if they cam from the Whos of Whoville," he wrote.

Mann, who is on sabbatical from Penn State, is spending half his year writing a book and the other half advising Environmental Health Sciences, publisher of the DailyClimate.org and EHN.org, on climate science.

He has no illusion that the latest findings will quash the debate over climate science.

"Climate change deniers continue to dredge up long-discredited talking points," he said. "This establishes that every credible body has found that there is no evidence at all for the allegations.

"It should be the final nail in the coffin," he added. "The only reason it won't be, if it isn't, is because climate change deniers are never willing to admit that they're wrong."

DailyClimate.org is a nonprofit news service covering climate change.

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.