Alarming predictions that global warming could cause sea levels to rise 6ft in the next century are wrong, it has emerged.
The forecast made by the influential 2007 Intergovernmental Panel on Climate Change, which would have seen cities around the world submerged by water, now looks ‘unlikely’.
A Met Office study also rules out the shutdown of the Atlantic Ocean’s conveyor belt, which would trigger Arctic winters in Britain like those seen in the film The Day After Tomorrow.
However, the report says the IPCC was right to warn of a sea level rise of up to 2ft by 2100, and that a 3ft rise could happen.
The IPCC underestimated the danger posed by the melting of the Greenland ice sheet and the release of methane from warmer wetlands, the report adds.
Vicky Pope, head of climate science at the Met Office, said: ‘In most cases, our new understanding has reinforced results from the IPCC report – and the degree of impact is about the same.’
The 2007 analysis was criticised last year after it was found to have wrongly claimed Himalayan glaciers could melt by 2035.
The Met Office analysis comes as world ministers fly to Cancun, Mexico, for the second week of UN climate change talks.
They will try to agree a treaty to curb greenhouse gas emissions and slow deforestation.
The talks, hosted at a Cancun luxury resort and golf spa famed for its beaches and water sports, have also attracted former deputy prime minister and keen diver John Prescott.
The new Met Office report is the first serious attempt to update the science of global warming since the publication of the IPCC Fourth Assessment.
The new Government funded study, says the worst case scenario is now a one metre (3.3 ft) rise.
In 2007 the IPCC reported preliminary evidence that the Atlantic conveyor belt that brings warm water north and keeps Britain relatively mild for its latitude during winters was breaking down.
But more recent observations show the currents are stable.
However, the report also has bad news. It says there is new evidence that the Arctic will become largely free of ice during most summers earlier in the century than the IPCC warned, and that the Greenland ice sheet is more likely to melt in centuries to come than previously thought.
It also warns that the release of methane from warming wetlands will be greater than thought in 2007 - leading to more global warming in the coming decades.
The Met Office report comes at the start of the second week of talks in Cancun designed to create a treaty that curbs greenhouse gas emissions, sets up a £60billion fund to help poor countries cope with climate change and slows down deforestation.
The 46 strong British delegation will be joined from today by Chris Huhne, junior Climate minister Greg Barker and Labour Peer Lord Prescott, Council of Europe’s Parliamentary Assembly Rapporteur.
The former deputy prime minister, who was involved in negotiating the original climate treaty in Kyoto, says he will present a “Prescott Plan” to break the deadlock between rich and poor countries.
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