By Matt Weaver
Tony Blair warns that the impact of climate change may be more serious than previously thought in a new government report on global warming published today.
The report raises fears that both the Antarctic and Greenland ice sheets are likely to melt, leading to a devastating rise in sea levels.
It warns of large-scale and irreversible disruption if temperatures rise by more than 3C (5.4F) - well within the range of climate change projections for the century.
Avoiding Dangerous Climate Change is published as a book and collates evidence presented by scientists at a conference hosted by the UK Meteorological Office last February.
The conference predicted that greenhouse gases would raise global temperatures by between 1.4C and 5.8C over this century.
"It is clear from the work presented that the risks of climate change may well be greater than we thought," Mr Blair wrote in the forward to the book.
"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 book includes concerns expressed by the head of the British Antarctic Survey, Professor Chris Rapley, that the huge West Antarctic ice sheet may be starting to disintegra
Scientists believe such an event would raise sea levels around the world by almost 5m (16 ft).
Prof Rapley writes that a previous report by the Intergovernmental Panel on Climate Change dismissing worries about the ice sheet's stability had to be revised: "The last IPCC report characterised Antarctica as a slumbering giant in terms of climate change. I would say it is now an awakened giant. There is real concern."
The report also warns that the EU may have to adopt tougher climate change targets. It is committed to preventing global temperatures rising by more than 2C, but the report warns that such a rise would trigger the melting of the Greenland ice sheet, prompting the extinction of the polar bear and the walrus.
The environment secretary, Margaret Beckett, said today's report highlighted the "tipping point" beyond which climate change could be expected to become irreversible.
This made it even more urgent to halt the change quickly, and meant that current targets - such as reducing carbon emissions by 60% by the middle of the century - may not be ambitious enough, she said.
"What is disturbing about the Exeter report is that it suggests that what has been a long-term policy framework, maybe even that is something that is going to cause more major difficulties than people imagined," she told BBC Radio 4's Today programme.
Mrs Beckett said she hoped to publish the government's climate change strategy - initially pencilled in for last year - in the near future, and certainly by the end of 2006.
She denied that the government had already decided to invest in new nuclear power stations as a way of cutting greenhouse gas emissions, but said the option had to be considered because of the role it could play in meeting the UK's long-term climate change targets.
"The reason we need to look at it very seriously is that the one thing you can say about nuclear power is that, once you have put in all the energy required to construct the nuclear power stations, it is actually a low-carbon form of energy," she said.
Friends of the Earth called for urgent action to cut greenhouse gases.
"Despite Tony Blair's concerns about climate change, UK emissions have risen under Labour," said FoE's climate change campaigner, Roger Higman.
"He should now support mounting calls for a new law requiring the government to make annual cuts in carbon dioxide emissions, and make Britain a world leader in the development of a low-carbon, nuclear-free economy."
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