Britain is to spearhead a new drive against climate change by bypassing President Bush and urging US states to join directly with Europe’s own carbon trading scheme.

David Miliband, the Environment Secretary, and MPs will travel to America in a fortnight for talks with states and the Democratic-controlled Senate which back limits on US greenhouse gas emissions. The Government hopes that nine northeastern states and California can eventually join the European Union’s carbon trading scheme in the first step towards a global scheme. The schemes are likely to prove far more effective by working together.

The developments came as the Intergovernmental Panel on Climate Change (IPCC) released its bleakest and most confident assessment yet of the science behind global warming. Its report, prepared by more than 2,500 scientists from 113 countries, predicted that average temperatures are likely to rise by 4C by the end of the century, and said human activities were “very likely” responsible.

Carbon trading schemes, pioneered in the EU, enable polluters to buy and sell emission permits, creating financial incentives to reduce production of greenhouse gases. The trip comes after a UN report published yesterday that confirmed that climate change was almost certainly man-made, and was likely to be far worse than previously thought. The Government said that, in the wake of the report, it would step up international efforts to reach a new global agreement on combating climate change, which would include both the US and developing countries such as India and China.

Ministers are also set to launch a campaign in Britain to encourage people to do more to reduce their own carbon emissions, including a new “carbon calculator” so that individuals can work out how much they are personally responsible for.

Mr Miliband told The Times last night: “The science is moving faster than the politics now. In 2007 we need significant progress at the international level. The UK is showing leadership with its Climate Change Bill, the EU is showing leadership and we hope that other legislatures across the world will take similar action.”

California and the nine northeastern states, frustrated by President Bush’s lack of action, have already set up their own carbon trading schemes. Arnold Schwarzenegger, the Governor of California, and George Pataki, Governor of New York, announced they would like to see ways to link up with the EU trading schemes. Despite good-will on both sides, the issue is fraught with difficulties, with the European Commission still having to resolve various legal issues.

Although there are signs that Mr Bush himself is finally beginning to shift ground, recognising climate change as a “serious problem” in his State of the Union speech last month, he still opposes capping carbon emissions. Mr Miliband will address the Washington Legislators Forum, which has been convened to take advantage of the opportunity created by the Democratic takeover of Congress last month.

Stephen Byers, the former Trade Secretary, will lead a discussion on how US states that have already set limits on greenhouse gases could be invited into the EU scheme. He said last night: “Some of the proposals will bypass the White House, others will engage with sympathetic Republicans. We are seeking to put pressure on President Bush.”

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