Every clause in the communiqué had been fought over for months, but the result was clear on three key points. It acknowledged climate change as a “serious long-term challenge”, held humans largely to blame and agreed on the need for urgent remedial action.

Will it make any difference to the temperature of the Earth’s surface? Experts thronging Gleneagles doubted it. But a clear shift in emphasis by President Bush, and a promise from Mr Blair to keep the issue high on the G8 agenda, makes progress more likely than three days ago. The deal makes no commitment to new action on carbon emissions limits for any of the G8 countries when the Kyoto Protocol expires in 2012. But outside the environmental movement it will be counted a success simply because the US signed up.

The nightmare scenario on climate change at this summit was American isolation. That was avoided by inserting caveats on the science of global warming, and committing the G8 to action towards “multiple objectives” rather than specifically cutting carbon emissions.

In return, US negotiators conceded a crucial phrase on human responsibility: “We know that increased need and use of energy from fossil fuels and other human activities contribute in large part to increases in greenhouse gases.” Another key sentence concerned the disputed science of climate change: “While uncertainty remains in our understanding of climate science, we know enough to act now.”

President Chirac was determined that the final communique recognise Kyoto’s role as the framework for fighting climate change outside the US, and he got his way, although not until the deal’s penultimate paragraph. However, President Bush has successfully shifted the focus of climate change politics away from Kyoto towards technology-based solutions with the involvement of the big developing economies. Kyoto’s failure to force India or China to cut emissions was a key reason that America rejected the protocol. The communiqué promises a partnership with major emerging economies that will include sharing American clean energy technologies.

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