CLAIMS prominent climate change scientists had recently received death threats have been revealed as an opportunistic ploy, with the Australian National University admitting that they occurred up to five years ago.

Only two of ANU's climate change scientists allegedly received death threats, the first in a letter posted in 2006-2007 and the other an offhand remark made in person 12 months ago.

Neither was officially reported to ACT Police or Australian Federal Police, despite such crimes carrying a 10-year prison sentence.

The outdated threats raised question marks over the timing of their release to the public, with claims they were aired last week to draw sympathy to scientists and their climate change cause.

The university denied it was creating a ruse, maintaining the initial report, in the Fairfax-owned Canberra Times last week, failed to indicate when the threats were made.

Reports also suggested the threats had forced the ANU to lock away its climate change scientists and policy advisers in a high-security complex. The Daily Telegraph has discovered the nine scientists and staff in question were merely given keyless swipe cards - routine security measures taken last year.

ANU climate institute director Professor Will Steffen, a key adviser to the Howard and Gillard governments, is believed to have received the threatening letter.

The other threat was made to a scientist at a university function last year by a person not known to university staff.

ANU communications director Catriona Jackson would not reveal the exact wording of the threats, but added: "Abusive emails are par for the course for most climate change scientists."

Scientist and renowned climate change sceptic Jo Nova said the revelation of the death threats was merely a welcome diversion for climate change believers.

"It's a great way to win sympathy. Not that I'm suggesting these scientists are feigning it themselves, but that there are billions of dollars on the table, not to mention a cult-like devotion to the meme," Ms Nova said.

"It's in quite a few people's interests to help those scientists win the sympathy of the crowd, and to distract the crowd with something non-scientific."

For more on the claims prominent climate change scientists had recently received death threats go to The Daily Telegraph.