The Copenhagen Climate Conference opened with a robust and angry defence of the science of global warming by two of the world's leading climate science figures.

Dr Rajendra Pachauri, the Nobel-Prize winning head of the UN's Intergovernmental Panel On Climate Change (IPCC), and Dr Jonathan Pershing, the head of the US delegation to the conference, both hit out at the theft of emails from the Climatic Research Unit of the University of East Anglia, which has been used by climate sceptics in Britain, the US and elsewhere to allege that global warming is not man-made.

There has been widespread speculation that the timing of the theft represented a specific attempt to destabilise the conference, in which the world community will attempt to construct a new treaty to cut back on the emissions of carbon dioxide causing the atmosphere to warm.

But yesterday Dr Pershing said that all the incident had done was to "release a barrage of further information which makes clear the robustness of the science".He said it was "shameful" how some of the scientists involved were now being pilloried.

Dr Pachauri told the conference opening ceremony, presided over by the Danish Prime Minister, Lars Lokke Rasmussen, that some people clearly found it "inconvenient" to accept the inevitability of the changes that would have to be made in the face of the climate change threat.

"The recent incident of stealing the emails of scientists at the University of East Anglia shows that some would go to the extent of carrying out illegal acts perhaps in an attempt to discredit the IPCC," he said.

The conference, being held at the giant Bella Centre in Copenhagen, brings together 192 countries, all of whom accept the verdict of the IPCC's most recent report, published in 2007, that the warming of the climate system is "unequivocal" and that there is a better than nine out of 10 chance that it is being caused by human actions - principally the emissions of carbon dioxide from industry, transport and deforestation, which retain the Sun's heat in the atmosphere.

Dr Pachauri listed some of the consequences of global warming.

They included increases in droughts and floods, greater stress on water resources, increases in tropical cyclone intensity, more extinction of wild species and the eventual melting of the Greenland ice sheet, which would cause sea levels around the world to rise by more than 6m.

This morning the negotiations proper get under way, with the aim being an agreement in which the industrialised countries such as the US and Britain make strong commitments to cut back their CO2 by up to 40 per cent by 2020, with the leading developing countries such as China and India making firm pledges to move away from "business as usual" in terms of their emissions growth.

Underpinning the deal will have to be a major new financial agreement which provides the developing nations with billions of dollars from the rich world in new climate aid, to help them cut their emissions and also adapt to climate change which is now probably unavoidable, such as widely increased flooding.

* How the scandal unfolded

Nov 19: Blogsite rumours suggest a hacker had obtained emails from University of East Anglia's Climate Research Unit computers.

Nov 20: The university confirms CRU documents appeared illegally on the web.

Nov 22: Auckland University scientist Chris de Freitas - a well-known sceptic of man-made global warming - tells the Epoch Times that the emails are "quite revealing".

Nov 23: Climate "sceptics" call for an inquiry after deciding the emails show data is being manipulated.

Nov 24: New Zealand climate scientist Jim Salinger confirms he is among those who have had their emails hacked into.

Dec 1: Man at centre of row, Professor Phil Jones, stands down while inquiry is conducted.

Dec 3: University of East Anglia commissions Sir Muir Russell, a former civil servant, to chair an independent inquiry.

Dec 4: Head of UN climate body says matter cannot be swept "under the carpet".

Dec 7: Niwa climate scientist David Wratt says data from 18 New Zealand climate stations will be published in the UK, as requested by the British Met Office.