An organised cyber-bullying campaign, including abusive emails, is targeting Australian climate scientists who speak out on climate change, according to author Clive Hamilton.

The 2009 Greens candidate says the attacks are arranged by "denialist organisations" and are aimed at driving climate scientists from the public debate.

Professor Hamilton says aggressive, abusive and sometimes threatening emails are being sent to distinguished scientists each time they speak out on the subject.

"Apart from the volume and viciousness of the emails, the campaign has two features - it is mostly anonymous and it appears to be orchestrated," he wrote in ABC's The Drum.

Professor Hamilton quotes an email received by University of Melbourne Professor David Karoly which compares the scientist's actions to those of Hitler, Stalin and Pol Pot.

"It is called treason and genocide," the email says.

"Oh, as a scientist, you have destroyed people's trust in my profession. You are a criminal. Lest we forget."

But some attacks are more personal.

Professor Hamilton says a young woman opened her email to receive threats against her children.

"Did you want to offer your children to be brutally gang-raped and then horribly tortured before being reminded of their parents' socialist beliefs and actions?" the email reportedly says.

"Burn in hell. Or in the main street, when the Australian public finally lynches you."

Journalists have also reportedly become targets of the cyber-bullying campaign.

"I have spoken to several, off the record, who have told of torrents of abusive emails when they report on climate change, including some sufficiently threatening for them to consult their supervisors and consider police action," he says.

"One or two of the cyber-bullies have hinted at the level of organisation, with one following an abusive rant with the comment,'Copies of my e-mails to you are also being passed out to a huge network for future reference'."

Professor Hamilton's article is the first in a five-part series. Tomorrow he will explore who is behind the cyber-bullying campaign.