The UN’s Intergovernmental Panel on Climate Change (IPCC) has warned that governments must cut carbon emissions at a faster rate than previously forecast and advised that fossil fuels be removed from the global energy mix by 2100.

However critics have responded, calling the report ‘alarmist’ and expressing alarm at the prospect of phasing out gas and coal-fired power too early.

In its latest assessment of global warming, which was published yesterday, the IPCC urged governments to cut carbon dioxide emissions by up to 70 per cent by 2050.

The report calculates that to prevent dangerous climate change, investment in low-carbon electricity and energy efficiency will have to rise by several hundred billion dollars a year before 2030. But it also found that delaying emission cuts to 2030 puts up the cost of reducing carbon dioxide by almost 50 per cent, partly because fossil power plants would have to be closed early. “If you wait, you also have to do more difficult and expensive things.”

The IPCC report also says that the required changes need only trim economic growth rates by a tiny fraction, and may actually improve growth by providing other benefits, such as cutting health-damaging air pollution.

As a means of avoiding an end of century fossil phase-out, it advocates the use of carbon capture and storage (CCS) and estimates that the cost of the big emissions cuts required would more than double without CCS.

Rajendra Pachauri, chair of the IPCC said: “With CCS it is entirely possible for fossil fuels to continue to be used on a large scale.”

‘In the absence of carbon capture and storage then power generation from fossil fuels would need to be phased out by the end of this century if we want to limit temperature increases to 2C.’

Professor Richard Tol of the University of Sussex in the UK and contributor to the IPCC, who claimed earlier panel reports were too “alarmist”, told the Financial Times It has been long known that smart policy can reduce greenhouse gas emissions at a small cost, even for deep cuts.”

The trouble was that smart policy would be a carbon tax that was equal for all emissions from all emitters, he said, and “all evidence to date is that governments compete on who can think of the daftest climate policies”, such as subsidies and tax breaks.

Earlier this year Tol withdrew his name from the final draft of the report in protest at what he believes is bias selection of the authors and evidence presented.

He was also unconvinced of the credibility of CCS as a solution to dilemma: “It is a long way until 2100 but carbon capture storage at a scale large enough to make a serious dent in emissions strikes me as optimistic. It would require too many pipelines, too much storage,” he said.