UNIVERSITY PARK, Pa., Aug. 23 (UPI) -- A climate scientist at the center of the climate-change debate has been exonerated of allegations of research misconduct, Penn State said in a statement.

Michael C. Mann, director of Penn State's Earth System Science Center, has been a target of climate change skeptics who have accused him of manipulating data, Chemical & Engineering News reported Tuesday.


"No direct evidence has been presented that indicates the Subject [Mann] fabricated the raw data he used for his research or falsified his results," a report by the National Science Foundation inspector general said.

Mann was one of a group of scientists whose e-mails were hacked from the University of East Anglia in the United Kingdom and made public in late 2009 as alleged evidence of manipulated data.

"I'm very pleased that the NSF office of the inspector general has confirmed what every other of the more than half-dozen investigations in the U.S. and Europe has established: that the various smears that have been manufactured by climate change deniers about me and other climate scientists have no basis in reality," Mann said after hearing of the NSF report.

In 2006, the National Research Council supported Mann's conclusions that climate warming in the Northern Hemisphere in the late 20th century was unprecedented during at least the last 1,000 years.