Attempts have been made to break into the offices of one of Canada's leading climate scientists. The victim was Andrew Weaver, a University of Victoria scientist and a key contributor to the work of the Inter-governmental Panel on Climate Change.

In one incident, an old computer was stolen and papers were disturbed.

In addition, individuals had tried to impersonate technicians in a bid to access data from his office, said Weaver.

The attempted breaches have heightened fears that climate-change deniers are mounting a campaign to discredit the work of leading meteorologists before the opening of the Copenhagen climate summit.

"The key thing is to try to find anybody who's involved in any aspect of the IPCC and find something that you can ... take out of context," said Weaver.

The prospect of more break-ins and hacking has forced researchers to step up computer security.

Fears of further attacks have also put delegates under increased pressure to reach a deal.