If you had said a decade ago that Al Gore would be organising the biggest rock concert in history, with two billion people watching and worrying about climate science, you would have been swiftly sectioned. But here we are: this weekend, the democratically elected 43rd President of the United States will be cheered on to the LiveEarth stage by hundreds of millions of viewers eager to know more about how we are, together, drastically altering the physical and chemical composition of our atmosphere.

Watch out on Saturday for the very first venue, because it is rapidly becoming the most important: Shanghai. This year, China overtook the United States as the biggest single emitter of greenhouse gases - way ahead of all the predictions. This tipping point is one of the biggest news stories of the year, and it's only the start: if current growth trends continue, China's emissions will exceed that of all industrialised countries combined by just 2030. But we have yet to redraw the map of green campaigning to catch up with this epochal shift.

The transformation of China today is so vast that it will be recorded by history as the Third Industrial Revolution. The positive consequences are plain to see: over 100 million people have been lifted out of near-permanant hunger in the past decade alone. But this is at the cost of an ecocide that will soon see that hunger return in ever-more vicious form if we don't adapt, fast.

China's cities are now lost in a permanant haze of smog that can render skyscrapers invisible at 100 feet. If you live in Beijing and simply breathe the air, it has the same effect on your lungs as smoking 20 high-tar cigarettes a day. Five of the country's largest rivers are now so toxic that it is dangerous to even touch them. The Pearl River has been renamed "The Black Dragon" because it runs black with toxins.

The effect of global warming on China is more vast still. Half of China's population live on the country's eastern seaboard - which will be drowned by just one metre of rising sea levels. The country's major rivers only flow because glaciers in the Himalayas catch snow in the winter and it melts off in the spring. But these glaciers are rapidly disappearing. How will the hundreds of millions of people dependent on this water - for growing their food, as well as for drinking and sanitation - survive?

So how can we adjust green campaigning to take account of all this? Should Hu Jintao - the Chinese dictator - become as intense a hate figure for greens as George Bush? The Climate Action Network ranks China 54th out of 56 countries for its response to global warming. Although the Chinese Communist dictatorship talks tough on global warming, the leeway given to green groups to make them act on their rhetoric is extremely limited. Only last year, an ordinary citizen called Tan Kai was tossed into prison for trying to set up a local environmental monitoring group called Green Watch.

But there are a few caveats here too. The average Chinese person still emits only a quarter of the greenhouse gases of the average American citizen, and half the gases of a European. They also point out that many of these Chinese emissions are, in fact, ours. We in Europe have mainly cut our greenhouse gas emissions not by cutting back our consumption but by transferring our polluting activities to Chinese factories. Your home is full of products made in these belching factories, and so is mine.

Nor should we buy into the racist rhetoric of seeing the Chinese as "faceless masses" represented by the government that oppresses them. Across China, brave citizens are rising up to fight their government over the environment. Last month, for example, a huge environmentalist demonstration was convened through forwarded text messages in the tropical seaport of Xiamen. More than 20,000 people faced down threats by the government that they would be fired from their jobs or even fired on.

So how do we side with these ordinary Chinese citizens who can foresee the looming disaster for their country and their planet? And - a logical next step - how do we lock China into a global agreement to reduce global warming emissions?

There is one simple concept that shows us the way forward, allowing the world's poor to develop without dooming us all. It is called Contraction and Convergence (C&C), and it was invented by the Global Commons Institute. The inventors of C&C point out that we already know that the level of greenhouse gases in the atmosphere needed to stay below a C20 rise, the point of no return. They call this amount of greenhouse gas emissions the world's "carbon budget".

The only fair way to divide out the world's carbon budget is to allocate an equal amount to each living human being. So under C&C, each country would be given a budget based on their population per head. There are then two stages. First, the rich countries would have to buy the right to their far higher emissions from the poor - in the process compensating the poor for the warming we have already caused. Second, the poor countries would gradually increase their emissions while the rich whittled them down, until we eventually converged in the middle.

The stance of the rich world at the moment - we emitted millions of tons while developing, but you had better not - is simply an insult, certain to fail. C&C is the only framework that could conceivably persuade the Chinese people to limit their emissions over time - and thereby save the world from runaway warming.

But there is a complicating factor. Even if we persuade the Chinese people, can we persuade the Chinese Communist Party? The CCP is acutely aware that its power is dependent on providing breakneck economic growth, because this anaesthetises the population against its lack of political freedom by providing higher incomes. They will resist any limit, even further down the line. This is why, when China's greatest green writer, Tang Xiyang, was asked what the country's biggest environmental problem was, he said: "Democracy. If you don't have democracy, you can't have real environmental protection."

So we need a two-pronged approach to China's swelling emissions: offer the Chinese people a fair deal, and support the democracy activists inside the country so they can force the dictatorship to accept it. We could start by shaming and stopping the Western corporations - including Yahoo and Google - who collaborate with the Chinese dictatorship in erecting the Great Firewall of China that prevents ordinary Chinese citizens from clicking on green groups' sites. So, yes, it is appropriate that LiveEarth starts in Shanghai. The fight against global warming will flare or die in that smoggy, angry city, and hundreds like it. The future of Earth depends now on how well we woo them.
(By Johann Hari, The Independent, 05/07/2007)