By Jeremy Lovell

LONDON, Nov 22 (Reuters) - The world is about to attempt the biggest transformation ever in the way the global economy works as it grapples with climate change, according to Britain's roving climate ambassador John Ashton.

Not only is it a vast task to wean the lumbering carbon dependent economies off their addiction, the climate crisis is so urgent that a there is no time for gentle cures.

"That is the most ambitious, the most complex, the most difficult piece of diplomacy that humanity will ever have attempted," Ashton said ahead of a meeting in Indonesia next month of world environment ministers.

The meeting on the island of Bali is designed to kick off two years of talks to agree a successor to the Kyoto protocol on cutting carbon emissions that expires in 2012.

"This is about getting a zero carbon energy economy by the middle of the century. That is a major political project," Ashton, climate change representative at Britain's foreign ministry, told Reuters.

The key was changing mindsets among the major economies such as the United States, Europe and Japan so that leading the way became seen as an attractive, profitable proposition.

"This won't work if we treat it like the trade negotiations, where nobody moves until everybody moves. The major economies, particularly the rich countries, need to be saying 'Follow me' not 'After you'," said Ashton.

"That is in essence what (British Prime Minister) Gordon Brown and the European leaders are saying", he added.

Scientists say global average temperatures will rise by between 1.8 and 4.0 degrees Celsius (3.2 and 7.2 degrees Fahrenheit) this century due to burning fossil fuels for power and transport, causing floods, droughts and famines.

Europe set a benchmark when in March it agreed that global temperatures could not be allowed to rise by more than two degrees Celsius above pre-industrial levels and set goals for cutting carbon emissions and boosting use of renewable energy.

TIME RUNNING OUT

But the consensus is fragile and everyone knows it.

Scientists and policy makers say there may be just a decade left to act before holding the line at two degrees becomes impossible and three or four degrees becomes inevitable.

"European leaders are at least telling European publics where they think the threshold of dangerous climate change is. Among the world's big economies, no other government is telling its public where the threshold lies," Ashton said.

"Some are saying lets talk about it or negotiate on it. Yet this is about the survival of civilisation," he added. (Reporting by Jeremy Lovell; editing by Keith Weir)

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