Bush's bluff has been called by China

Even for George Bush, the apostle of climate-change deniers, an out-and-out obstructionist US positi

That climate change was top of the agenda at this year's G8 summit in Heiligendamm, Germany, is a measure of how far the issue has come to dominate the international stage. Three or more years ago, it only ever featured on the banners of protesters. What was marginal has become mainstream.

Even for George Bush, the apostle of climate-change deniers, an out-and-out obstructionist US position is no longer tenable. Rather than calling the science "uncertain", Bush realises he has been left isolated by a transformation of the US domestic political scene. He has had to resort to damage limitation, such as his agreement to "consider" US participation in a G8 initiative to cut global emissions by 50 per cent by 2050, announced at the summit on 7 June.

The climate-change rug has been pulled from under Bush's feet thanks largely to the efforts of three key people - all American. One is Al Gore, who has invested most of his political capital and new-found star status in pushing climate to the top of the US domestic agenda. Second is Greg Nickels, mayor of Seattle, who started a campaign in 2005 to get US mayors to unilaterally opt into Kyoto just as President Bush had unilaterally opted out. At the latest count, 527 mayors, representing over 66 million Americans, had signed up.

The third person was the biggest coup of all: Arnold Schwarzenegger, governor of California, who has pioneered state-level partnerships to address global warming by setting up the Western Regional Climate Action Initiative, which now includes Utah, Arizona, New Mexico, Oregon and Washington, as well as his own California. The psychological effect of Arnie's support should not be underestimated - not only is he a Republican, but he has made caring about the climate respectable among red-blooded, Hummer-driving American males. No one need worry about looking a bleeding-heart liberal if they have the Terminator on their side.

Bush is simply following these real leaders when he admits that the US will one day have to reduce its greenhouse gas emissions. This sends a crucial signal to American business that regulation is coming - perhaps in as little as two years - and that it needs to prepare for the inevitable. In such conditions even big polluters begin to cry out for political action which gives them a long-term framework for making investment decisions. Bush will be history by 2009, and it is now inconceivable that a new administration of either party could keep the US out of the next phase of Kyoto.

For years Bush has cited the Chinese as his main reason for opting out of Kyoto. The US argued that a greenhouse-gas commitment would make US goods less competitive than China's. Now the Chinese have called America's bluff.

On 4 June, Beijing released its climate change plan, which officially confirmed the country's indefinite refusal to countenance any future emissions targets. Instead, President Hu Jintao reminded the G8 of the UN principle of "common but differentiated responsibilities", where-by industrialised countries - which have both the highest historical responsibility for past emissions and the largest current per capita emissions - must take the lead. As Chinese officials stated, the country may be the world's second-largest emitter, but if every country had per-capita emissions as low as China's (about four tonnes of CO2 per person per year; the US's are 20) there would be no climate-change problem. Ominously, India's leadership is now lining up behind the Chinese position.

This stalemate will continue until Bush leaves office. Once a successor is in place, and the US has demonstrated a real commitment to taking on dramatic cuts - only then will China and India reconsider. In all likelihood, any future framework will take the form of "contraction and convergence".

All this brinkmanship will, of course, lose us still more valuable time. To keep global temperatures from crossing the dangerous 2°C line (EU policy) global emissions must peak within the next eight years. In other words, we need to stop talking about 2050 and start talking about 2015. The 2°C time bomb is ticking and we'll need a global emergency action plan to defuse it.