ONCE he was the nearly man of American politics, but this weekend Al Gore, Bill Clinton’s former sidekick, made it clear he was back, no longer just a politician but a phenomenon: the first global green celebrity.

As the Live Earth concerts rolled out around the globe, each blessed with Gore’s presence, either live or on giant screens, it became clear that the failed presidential candidate has metamorphosed into a prophet.

In an interview with The Sunday Times before yesterday’s Live Earth concert at Wembley, the former vice-president revealed that the concerts are only part of a grand excercise whose ambitions are nothing less than the rebranding of climate change.

“The Live Earth concerts are just the opening shot,” he said. “We’re following it with a three-year global campaign to win popular support for reducing emissions.

“What is holding the world back from dealing with global warming is the lack of public understanding.

“If the majority of people here, where there has been so much excellent media coverage of global warming, still don’t accept the scientific consensus, then we need to increase awareness some other way. That is why politicians cannot do anything about it. And that is why we’re doing this concert.”

Live Earth, with concerts in all seven continents including Ant-arctica, is thought to have been one of the biggest coordinated global events in history.

Critics question whether a pop concert, however large, really has the power to make people take climate change more seriously. Others point to deeper contradictions. How, they ask, can an event epitomising global consumerism be a valid way of tackling a problem largely created by the West’s conspicuous overconsumption?

Gore believes that such objections are trivial. “Our team has done a great job in offsetting the emissions we create,” he said. “In any case, how else can we get the attention of the world onto this crisis?”

At the heart of Gore’s hopes for Live Earth’s success are seven climate pledges. These call on supporters to cut their own carbon dioxide emissions; to deal only with companies with similar ideals, and to put pressure on politicians, businesses and other organisations to do the same.

“If we can get just 50%-60% of people to accept the scientific consensus on climate change, then we would make it possible for political leaders to take the strong action we need,” he said.

He is cautious about describing just what kind of action that might be and Gore is unwilling to go too far. “I agree we need to change our living patterns,” he said, “but I think it will be new ideas and technological developments that will make it possible to sharply reduce our carbon dioxide emissions.”

Gore praised Britain for the high profile it had taken in combating climate change, but said its actual record of rising emissions was disappointing.

“Last week there was a Mori poll showing that even in Britain nearly 60% of people do not accept that humans are the main cause of climate change. Those people think, wrongly, that the scientific debate is still raging.

“Britain’s emissions have been rising in recent years. That is just another reason why it is so important to bring about a massive shift in public opinion, so that more pressure is put on politicians.”

The campaign was never meant to be a vehicle for Gore’s political return, but, in many people’s eyes, progress on dealing with climate change, especially in America, is now inextricably bound up with his own political future.

When he accepted defeat by George W Bush in the 2000 pres-diential election, even though he won the popular vote, it seemed that he was finished. But in 2001 he began travelling the world delivering a lecture and slide-show on global warming that he had perfected before becoming vice-president in 1992.

Gore had been obsessed with climate change since he was a student at Harvard in the 1960s. After election to the House of Representatives, aged 28, he held the first congressional hearings into global warming in 1980, and in 1992 he wrote Earth in the Balance, a book setting out the climate change challenge. His lecture, rather than his books or politicking, lies behind his rise to cult status.

That began in 2005 when Lau-rie David, a former comedy producer but now an environmental activist, brought Gore to Hollywood’s Beverly Hilton hotel. Among the audience was Law-rence Bender, producer of Pulp Fiction, who immediately saw the potential. “I thought to myself, this has got to be a movie,” he said.

The result was An Inconvenient Truth, the first film based on a PowerPoint presentation to win an Oscar. It has also turned Gore from a has-been back into a gonna-be who understands the need to maintain momentum.

Frank Furedi, professor of sociology at Kent University, believes that Gore is also rebranding himself, using the modern obsession with celebrity to bypass the political process. “Gore has successfully harnessed the appeal of celebrity culture to boost his moral crusade,” said Furedi. In America there are “Draft Gore” websites and a political action committee. When pressed, Gore will say only that although he is reluctant to run again he is “not ruling it out completely”.

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