Washington - A ten-fold increase in productivity per unit of carbon emissions over the next decades would balance the needs of the world to slow down global warming while maintaining economic health, according to a report released Saturday at global climate talks of lead industrial and emerging economies.

The report, prepared by a team of research economists at a global private think tank, was produced for a gathering of legislators in Tokyo from Saturday to Monday.

Presiding at the meeting will be Japanese Prime Minister Yasuo Fukuda and former British Prime Minister Tony Blair, who is pushing the Group of Eight (G8) leaders to agree on the ambitious target to halve greenhouse gas emissions by 2050 during their July summit in Japan.

Senior legislators from across the G8 and major emerging economies of Brazil, China, India, Mexico & South Africa were gathering at the behest of the British-led environmental group Global Legislators Organisation for a Balanced Environment (Globe).

Proposals coming out of the gathering are to be presented to the leaders of the G8 in July.

The report, prepared by McKinsey Global Institute, suggests that productivity - Gross Domestic Product (GDP) - must grow from the current 740 dollars per ton of greenhouse gas emissions to 7,300 dollars per ton by 2050.

The economists compared such a change to the Industrial Revolution, which saw a ten-fold increase in labour productivity over a similar period of time.

The economic costs of such a "carbon revolution" would be "manageable" at 0.6 to 1.4 per cent of global GDP by 2030, the McKinsey economists said.

Without improved productivity, the report outlined the individual sacrifices people would need to make to meet commonly discussed per- person targets of 6 kilograms of greenhouse emissions per day.

"If one had to live on such a carbon budget with today's low levels of carbon productivity, one would be forced to choose between a 40-kilometre car ride, a day of air conditioning, buying two new T- shirts without driving to the shop, or eating two meals," the report said.

Such stringent restrictions would entail a "major drop in lifestyle for developed countries and would hinder economic development in low income countries," the report said.

Economists and climate scientists have variously put the cost of improving technology and reducing consumption of fossil fuels at 0.06 to 0.12 per cent of world GDP. The cumulative effect would reduce GDP by 2.5 per cent by 2030 and 4 per cent by 2050.

At present, diplomats around the world are debating whether, and how, they will be able to replace the Kyoto Protocol on climate change when it expires in 2012. The participation of the world's richest countries is seen as crucial to any deal.

But the Group of Eight (G8), due to meet in Toyako on the Japanese island of Hokkaido on July 7-9, is bitterly divided.

Four members - European Union heavyweights Germany, Britain, France and Italy - have already pledged to cut their emissions of carbon dioxide by 20 per cent no matter what the world does, and 30 per cent if other major powers do the same.

But the United States, which refused to ratify Kyoto out of fears that it could harm the US economy, insists that it will not sign up to any emissions-reduction deal which does not impose strict limits on rising powers - and potential rivals - China and India. (dpa)