A landmark and largest ever U.N. climate summit opened here on Monday, with the head of the U.N.’s Nobel-winning panel of environmental scientists accusing vested quarters of not being ready to face the reality of threats of wide-ranging nature of changes in climate.

Attacking the so-called “climategate” affair as a bid to undermine the capability of his organisation, Rajendra Pachauri said at the opening ceremony that those who had hacked into the e-mails of top climate scientists were out to discredit the scientific assessment made of threats to the climate.

But “climategate” rocked the conference with some countries calling for an international probe into the affair, especially accusations that scientists had distorted data to dramatise the threat of global warming.

The Saudi Arabian negotiator Mohammed al-Sabban said that climate science had been “shaken” by the leaked e-mails. “The level of trust is definitely shaken, now that we are about to conclude an agreement that... is going to mean sacrifices for our economies.”

However, Mr. Pachauri stoutly defended his organisation, the Intergovernmental Panel on Climate Change, saying, “Giving the wide-ranging nature of change of that is likely to be taken in hand, some naturally find it inconvenient to accept its inevitability.”

“The recent incident of stealing the e-mails of scientists at the University of East Anglia shows that some would go to the extent of carrying out illegal acts perhaps in the attempt to discredit the IPCC,” the scientist said.

He said that the stealing of e-mails exchanged between scientists from a U.K. university indicated the extreme measures some people would adopt to deny the existence of climate change.

Mr. Pachauri defended the scientific integrity of the body as well as its contributors including the scientists caught up in the e-mail controversy.

Hackers gained access to the data of the climate research centre of the university and leaked confidential data including thousands of e-mails and documents between British and U.S. scientists over the past ten years that have led to accusations that scientists amplified the nature and scope of the manmade climate crisis.

Some of the excerpts of the e-mails posted read, “I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (i.e. from 1981 onwards) and from 1961 for Keith’s to hide the decline.

Another e-mail reads: “The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t.”

Sceptics of climate change have used these e-mails to back their case that the dangers of climate change have been wildly exaggerated on several Websites and blogs.