Members of the Nobel-winning panel of climate scientists rose on Tuesday to defend colleagues that they said had been "targeted" for email hacking to sway the outcome of the UN global warming talks.

Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change (IPCC), said he believed the email intercept was a calculated act.

"The persons who have worked on this report, and those who unfortunately have been victims of this terrible and illegal act, are outstanding scientists, and have contributed enormously over the 20, 21 years of the existence of the IPCC," he told a press conference at the UN climate talks here.

He added: "I believe they are being unfairly targeted."

The thousands of intercepted emails have been seized upon by skeptics as "Climategate" -- evidence that scientists twisted data in order to dramatise global warming.

Some of the thousands of messages, purloined from scientists at Britain's University of East Anglia, a top centre for climate research, expressed frustration at the scientists' inability to explain what they described as a temporary slowdown in warming.

They also discussed ways to counter the campaigns of climate naysayers.

The authors, though, say their messages are sometimes flippant or ironic, and are being distorted to suit denialists.

Pachauri dismissed contentions that the IPCC's landmark Fourth Assessment Report should be revisited.

In 2007, this phonebook-sized study declared that the evidence of warming was "unequivocal" and damage to glaciers, snowfall and changing seasons were among the signs that climate change was already on the march.

"I think this is an illegal act. The only issue that has to be dealt with as far as this occurrence is concerned is to find out who is behind it," said Pachauri.

"One can only surmise that those who have carried out this act have done it with the very clear intention to influence the process in Copenhagen -- but, barring a few isolated voices, people over here are totally convinced of the solidity of the findings in the IPCC report."

Yvo de Boer, executive secretary of the UN Framework Convention on Climate Change (UNFCCC), said the incident had had scant impact at the Copenhagen talks and insisted the IPCC's integrity remained untouched.

"I do not believe that it has damaged the credibility of IPCC, given the fact that that is a process where 2,500 scientists do not research themselves but review works that had been published and peer reviewed," he said.

"I think the science produced by the IPCC is rock-solid," he added.

Pachauri said his panel would probe the incident "just to see if there are any lessons for us that we might want to take onboard.

"We are determining how best to do that. But I want to clarify that this is not an investigation."

On Monday, Saudi Arabia seized the opening sessions of the UN climate talks to say that public trust in climate science had been "shaken" and an independent probe was needed.

"I would have been concerned if they hadn't made an issue of it," Pachauri said drily.

"Wouldn't you expect that? Oil and politics mix very well. I'm not too sure that oil and science mixes very well."

Separately, the IPCC's Working Group 1 -- gathering the scientists who made the "unequivocal" judgement -- said it "firmly stands" behind its work and the exhaustive process of open debate and independent peer review.

"The body of evidence is the result of the careful and painstaking work of hundreds of scientists worldwide.

"The internal consistency from multiple lines of evidence strongly supports the work of the scientific community, including those individuals singled out in these email exchanges, many of whom have dedicated their time and effort... during the past 20 years."