INTERNATIONAL action to halt climate change must be taken within 20 years or global warming will be irreversible, scientists said yesterday.

By 2025 the technology needs to be in place to reduce carbon emissions by 2.6 per cent every year to avoid catastrophic climate change. Leaving it any later will mean that so much carbon dioxide has been released into the atmosphere that it will no longer be feasible to reduce levels sufficiently, the Royal Society was told yesterday.

The rate of global warming is already worse than was feared in 2001, with melting ice likely to increase sea levels by up to 40ft unless temperatures are stabilised. In the Antarctic an area of ice big enough to swallow Britain almost three times over could float away and melt.

A report published yesterday to provide a comprehensive analysis of climate research gives warning of irreversible damage to the ecosystem unless action is taken on an international level. Tony Blair, writing the foreword to the report, said: “It is now plain that the emission of greenhouse gases, associated with industrialisation and economic growth from a world population that has increased six-fold in 200 years, is causing global warming at a rate that is unsustainable.”

The report, Avoiding Dangerous Climate Change, collates evidence presented by scientists at a conference hosted by the Met Office at Exeter last February. Its stark conclusion is that too little is being done to stem climate change and that the rate of change is far worse than feared.

Among the aims of the conference was to identify the “tipping points” of global warming, the rises in temperature at which it becomes impossible to halt change. At the publication of the report at the Royal Society in London last night, Rachel Warren, of the Tyndall Centre for Climate Change Research, told an audience of scientists and policy-makers that governments have 20 years in which to act.

Citing research from the Netherlands, she said that European countries had accepted a 2C rise in temperature as the maximum that should be permitted. “If we are going to have a reasonable chance of limiting the change to 2C, emissions need to peak in 2025. From then they need to be reduced by 2.6 per cent per year,” Dr Warren said.

Terry Barker, of the Tyndall Centre, called for the introduction of a carbon tax as the best and possibly only effective means of forcing industry to reduce emissions. According to a computer model devised by Dr Barker, if governments agree to such a tax at the same time as encouraging investment in anti-emission technology, emissions will be radically reduced within decades.

The report identifies the melting of the ice sheets as among the most serious results of global warming. The Greenland ice sheet is already reducing and research predicts that a 2.7C rise in temperatures is the point at which this becomes irreversible, though it is likely to take centuries for the process to finish. Estimates of temperature rises this century range from 1.4C to 5.8C.

Chris Rapley, of the British Antarctic Survey, said that the western Antarctic ice sheet had begun to disintegrate at an alarming rate since the Intergovernmental Panel on Climate Change report of 2001, when the continent was regarded as stable.

His collegue, David Vaughan, said yesterday that the loss of ice in Greenland and the western Antarctic would each be likely to increase sea levels by 16ft or more.

Another crucial point identified by the report was the 1C rise that would see extensive acidification of the oceans, killing off many life forms, including 80 per cent of corals.

Margaret Beckett, the Environment Secretary, said the conference could force a rethink on policy and on the target of reducing emissions by 60 per cent by the middle of the century.

THE REPORT’S WARNINGS

• Limiting temperature increase to 2C above pre-industrial levels should stabilise carbon dioxide concentration to 450 parts per million (ppm). A concentration of 550ppm would make a 2C maximum increase virtually impossible
  
  
• A 1C rise in temperature would lead to 80 per cent of the oceans’ corals being destroyed. A 2.7C rise would lead to the irreversible melting of Greenland’s ice sheet
  
  
• Temperatures are predicted to rise by between 1.4C and 5.8C by the end of the century. Since 1765 average temperatures have risen by 0.7C. Of this, 0.1C has taken place since 1990
  
  
• If action to reduce emissions is delayed by 20 years, rates of reduction will need to be up to seven times greater to meet the same target

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