Climate Scientists Claim 'McCarthy-Like Threats,' Intimidation

"Climate scientist Michael Mann says he has received hundreds of them -- threatening e-mails and phone calls calling him a criminal, a communist or worse.

'6 feet under, with the roots, is were you should be,' one e-mail reads. 'How know 1 one has been the livin p*ss out of you yet, i was hopin i would see the news that you commited suicide, Do it.'

'I've been called just about everything in the book,' Mann, who runs of the Earth System Science Center at Penn State University, told ABC News. 'It's an attempt to chill the discourse, and I think that's what's most disconcerting.'

Mann is not the only one. The FBI says it's seeing an uptick in threatening communications to climate scientists. Recently, a white supremacist website posted Mann's picture alongside several of his colleagues with the word 'Jew' next to each image.

One climate scientist, who did not wish to be identified, told ABC News he's had a dead animal left on his doorstep, and now sometimes travels with bodyguards. "

Dan Harris and Christine Brouwer report for ABC News May 23, 2010.