The G8 summit in Heiligendamm ended amid predictable carping from the side-lines. The rich countries’ £30 billion commitments to Africa were dismissed by Bob Geldof as a “total farce”. Seldom can relations in the G8 have been as strained as with Russia: Tony Blair warned after meeting Vladimir Putin that “real issues” remained to be resolved.

However, it would be wrong to dismiss the G8 gathering as just another photo opportunity. A breakthrough was made on climate change, most importantly by bringing the Americans on board. The Bush White House, in signing up to a statement that blamed global warming firmly on human activities and endorsed a programme of “substantial” emission reductions, has moved a long way.

Not so long ago the White House’s advisers were rejecting the science of global warming. Then they denied a man-made contribution. More recently, at Gleneagles two years ago, Mr Bush would acknowledge only the need for new technology in tackling climate change. Now he has agreed to much more, moving significantly closer to the international consensus, including the prospect of a post Kyoto international framework built not just around technology but also a global market in carbon emissions, curbing deforestation and other measures.

Mr Bush has moved and his successor will move further. America has not signed up for a specific target to cut emissions but it will. The G8’s communiqué referred to the proposed reductions of more than 50% by 2050 in the European Union, Canada and Japan. Public opinion in America is shifting; 522 mayors representing 65m citizens have signed up to Kyoto-style emission reductions. In New York, where Michael Bloomberg, the mayor, has committed the city to 30% emission cuts by 2030, cab drivers are switching to hybrid vehicles. Even in Texas things are changing: in Austin, the state capital, new homes will use 60% less energy by 2015.

The big issue is whether the two emerging economic giants, China and India, each with more than a billion people, can be brought on board. China is the world’s second largest energy consumer and will soon overtake America’s carbon emissions; India is fifth. A third of the world’s coal is burnt in China, with a new coal-fired power station opening every few days. How can China’s and India’s growth possibly be green?

The challenges are huge but the picture is not as gloomy as sometimes portrayed. China and India, along with Brazil, Mexico and South Africa, signed a joint declaration with the G8 on Friday pledging to contribute their fair share to tackling climate change by stabilising greenhouse gas emission levels in the atmosphere.

In both China and India, political leaders are aware that global warming could bring more misery to their people than in the West. China is a world leader in solar energy and the manufacture of low-energy light bulbs. Both countries are developing alternative energy sources. Price Waterhouse Coopers demonstrated last year that a significant reduction in global emissions by 2050 was possible, alongside economic growth, provided the West took the lead in reducing its emissions. China and India would need greener growth than now but would not have to face unrealistic targets.

Can it be done? Three things are needed. The first is the right economic incentives through a properly functioning global emissions trading scheme. Give businesses the financial incentive to cut emissions and they will do so, wherever they are based. Good businesses will make money out of it. The second is that technology which cuts emissions, whether carbon capture and storage, hybrid engines or hydrogen power, has to be made freely available. This is one area where technology transfer is of global benefit. Finally, there has to be the political will. At the G8 we saw that political will on display. And that is something to be hopeful about.