The United Nations panel on climate change has strongly defended scientists at the centre of a row over alleged manipulation of data.
Climate sceptics say leaked emails from the University of East Anglia in England show scientists have exaggerated how much human behaviour is warming the planet, reports the BBC.
But the UN Panel on Climate Change say scientists around the world support the evidence of global warming.
The vice president of the IPCC, Jean Pascal van Ypersele says there was a purpose in the leaking of the emails.
He claims unnamed conspirators could have paid for Russian hackers to break into the university computers to steal the emails.
Professor van Ypersele says the theft was a scandal and was "probably ordered" to disrupt the confidence negotiators have in the science.
He says even if the evidence of those scientists is removed, it does not change anything to the IPCC conclusion.
Indian PM to attend
Indian Prime Minister Manmohan Singh is the latest leader to announce he will attend the closing stages of this week's climate summit.
Denmark's Prime Minister, Lars Lokke Rasmussen, said India was key to global efforts to tackle climate change.
India is the world's fourth biggest emitter of greenhouse gases, and has recently announced a target of cutting emissions by between 20% and 25% from 2005 levels by 2020.
Earlier, US President Barack Obama announced he had changed his plans and would attend the end of the conference rather than its early stages.
Mr Singh's decision brings the number of leaders attending the summit to 105, including New Zealand Prime Minister, John Key.
Demonstrators increase pressure for deal
Climate activists in Europe staged protests on Saturday to add pressure on leaders to agree a strong deal.
About 20,000 people marched in London, while a Greenpeace demonstration in Paris drew 1,500 people.
Activists in Berlin, posing as world leaders, sat inside a giant aquarium that was gradually filled with water to highlight the risks of rising sea levels from melting glaciers and ice sheets.
Delegates from 190 nations are gathering for the start of the 7-18 December meeting. The talks are aimed at working out a new pact to curb climate change after the first phase of the Kyoto Protocol ends in 2012.