The cuts in greenhouse gas emissions being proposed at the Copenhagen climate conference, which opens today, are completely inadequate to stop dangerous climate change, one of Britain’s leading climate scientists warns.

Current proposals, including recent ones from major emitting nations such as the US, China and India, are “little more than token gestures”, compared to what the science deems necessary to give even a 50-50 chance of staying below the danger threshold, says Professor Kevin Anderson, Director of the Tyndall Centre for Climate Change Research at the University of Manchester.

Writing in The Independent today, Professor Anderson cautions that with the commitments currently on the table in Copenhagen, global emissions of carbon dioxide will peak far too late for temperature rises to stay below two degrees Centigrade above the pre-industrial level, which is regarded as the limit that the earth and human society can safely stand.

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Instead, they are likely to put the world on a disastrous trajectory for four degrees or even higher.

Nations must now make much more radical commitments, he says, even if it means sacrificing economic growth.

Professor Anderson is one of the world’s leading experts on CO2 emissions rates, and his comments represent a sobering reality check about just how great is the task which the world now faces in bringing global warming under control.

The meeting in the Danish capital, which lasts for the next two weeks and will be attended in its final stages by most of the world’s leaders including President Barack Obama and Gordon Brown, will attempt to construct a new climate treaty under which all countries will eventually cut back their CO2.

In the run-up to the conference, most of the world’s biggest carbon emitters, led by China and the USA, and including the European Union and Britain, have “put numbers on the table” indicating the reductions they are prepared to make, if negotiations are successful in the round.

The targets announced for the first time in the last fortnight by America, China and India, in particular, have been regarded as a considerable step forward.

But the sum of all the commitments is simply inadequate for the point where emissions peak as a whole and then start to decline to come early enough, Professor Anderson says.

The date of the emissions peak is increasingly seen as a vital point in checking the progress of the warming.

Last year, the Met Office’s Hadley Centre for climate prediction and research said that if global emissions peaked in 2015 or 2016 and then declined annually at a rate of four per cent, there would be a 50-50 chance – but no more than that – of keeping the rise in temperatures to two degrees, the goal upon which much of the world’s climate policy is premised.

For every ten years that the peak was delayed, the Hadley Centre said, the world would be committed to another 0.5 of a degree of warming.

Professor Anderson points out that there is a widespread assumption that an emissions peak might come relatively early, but asserts that the political and economic will to bring this about is actually absent.

He writes: “For example, the [Lord] Stern and the [UK] Committee on Climate Change reports are premised on global emissions reaching their highest levels by 2015 and 2016 respectively, before beginning a process of year-on-year reductions.”

He goes on: “However, amongst those working on climate change there is near universal acknowledgment that such early peaking years are politically unacceptable – yet the Stern and the CCC analyses remain pivotal in the formation of emission-reduction policy.

“The statements by the US, China and India, allied with commitments from other nations, suggest peaking global emissions between 2020 and 2030 is about as hard as the economic and political orthodoxy is prepared to push in terms of emission reductions.

“If peaking global emissions between 2020 and 2030 is left unquestioned, the cumulative quantity of greenhouse gases emitted will be sufficient to put temperatures on a 4 degrees C or higher trajectory.”

In recent years, emissions have shot up in a way no-one expected even a decade ago, largely owing to the breakneck industrialisation of China, which doubled its CO2 output over the decade from 3bn to 6 bn tonnes, and in doing so overtook the US as the world’s biggest polluter. Currently global carbon emissions are rising by nearly three per cent annually, making a four per cent annual decline as tall order indeed, and one that the present Copenhagen commitments would not remotely be able to facilitate.

There has to be a move to a radical new level of emissions cuts, Professor Anderson says, if dangerous climate change is to be avoided.

He writes: “If Copenhagen is to have any chance of kick-starting a global movement to stay below the 2 degrees C characterisation of dangerous climate change, it must inspire and instigate a rapid shift away from the current political and economic consensus.”

The first challenge, he says, is to get political buy-in to what the science is saying in relation to, at least, a 50:50 chance of not exceeding 2 degrees C.

“In brief, wealthy (OECD) nations need to peak emissions by around 2012, achieve at least a 60 per cent reduction in emissions from energy by 2020, and fully decarbonise their energy systems by 2030 at the latest.

“Alongside this, the ‘industrialising’ nations (non-OECD) need to peak their collective emissions by around 2025 and fully decarbonise their energy systems by 2050.”

He notes: “This scale of reductions is presently far removed from that which the negotiators in Copenhagen are intending to consider.”

He concludes: “The second challenge for Copenhagen, therefore, is to make a clear and explicit decision to do all that is necessary to put global emissions on a 2 degrees C pathway, even if this requires a temporary cessation in economic growth amongst the wealthy OECD nations.”

* On the eve of the conference yesterday, the UN’s top climate change official expressed confidence that the meeting would deliver a comprehensive, ambitious and effective international climate change deal. “Negotiators now have the clearest signal ever from world leaders to craft solid proposals to implement rapid action,” said Yvo de Boer, Executive Secretary of the UN Framework Convention on Climate Change (UNFCCC).

Mr de Boer said there was unprecedented political momentum to clinch an ambitious deal in Copenhagen: “Never in 17 years of climate negotiations have so many different nations made so many firm pledges together.

“So whilst there will be more steps on the road to a safe climate future, Copenhagen is already a turning point in the international response to climate change.”

However, climate sceptics will be boosted by the fact that the controversy over the stolen emails from the Climatic Research Unit of the University of East Anglia, which has been seized on by the sceptic lobby seeking to undermine the scientific consensus, will receive an airing at the conference today. Mr de Boer said that Dr Raj Pachauri, the chairman of the Intergovernmental Panel on Climate Change, IPCC, would refer to it in his speech during the opening ceremonies.

The UNFCCC secretariat revealed last night that 34,000 people had applied for accreditation to the meeting, taking place in a conference centre which only holds 15,000. The limit on accreditation of journalists has already been reached at 3,500 and further accreditation has been suspended, while environmental groups are being rationed as to the numbers of activists who are allowed on the site.