Like all groups that decide policy by committee, the Intergovernmental Panel on Climate Change (IPCC) is naturally prone to conservatism.

Every line in its Summary for Policymakers is fiercely contested, and must be approved by a consensus of more than 300 expert scientists before it is included in the final document.

The panel’s uncharacteristically robust conclusion that global warming is "very likely" the result of human activity is therefore cause indeed to declare the debate over, as David Miliband, the Environment Secretary, has done this morning.

Much of the report’s significance lies in the way its language has become more confident since the IPCC’s last effort. Where the 2001 document found "new and stronger" evidence that most warming is human-induced, the new one declares there is more than a 90 per cent chance that this is so.

A graph, published on page 16, makes this particularly plain. A series of long bars show how gases produced by humans have contributed to rising temperatures, above a stubby one detailing the influence of the Sun — the favoured alternative of the greenhouse deniers.

Even sceptics have stopped claiming that global warming is not happening. It will now be harder than ever for them to argue that temperatures might be going up, but that we are not responsible.

The 90-per cent confidence level might leave some room for uncertainty, but, as the Met Office has pointed out, every business makes decisions based on probabilities that are far lower.

There are other important new conclusions, too. The panel now thinks that temperatures are in line to rise even more steeply than it did six years ago: the likely increase by 2100 is up from 3C to 4C, and the maximum is up from 5.8C to 6.4C.

Another significant figure is the probable increase given a doubling of pre-industrial carbon dioxide levels to 550 parts per million — a figure that the government thinks could be politically achievable.

Even that target will lead to likely temperature changes of between 2C and 4.5C, with a best estimate of 3C. Without drastic action to curb emissions, the world is clearly going to get a lot warmer.

It is also interesting that the IPCC has assessed it as "likely" — a better than 66 per cent chance — that global warming is increasing the intensity of hurricanes and other tropical storms. Previous reports have steered clear of this issue, but a wealth of evidence published in the past three years has now shown that hurricanes are almost certainly getting stronger, if not more frequent.

Times Recommends

• A vicar’s wife: ‘There is no one to fight for us’
• Every little helps at the supermarket
• Ugg or Fitflop? The battle of the boots