"Half of all emissions have been since 1980. I think people lose track of the rate of acceleration. You tend to think of (this as) something that's been going on -- it's not," he told Reuters late on Thursday.

Rising emissions of carbon dioxide and other greenhouse gases risk contributing to severe climate change, including rises in sea levels and extreme weather, many scientists say.

They say dramatic cuts in emissions are needed by mid-century to reduce the scale of such changes, and the steep rise in emissions in recent years underscores the size of the task facing governments round the world.

The CDIAC estimates that global carbon emissions rose some 200 million tonnes to 7.9 billion tonnes in 2005, 28 percent above 1990 levels. This followed a rise of nearly 5 percent in 2004, it said.

The 2004 and 2005 estimates were based on energy data published by the oil company BP, while its pre-2004 work used UN energy data.

"The last couple of years are always subject to revision but I think they're pretty sound," Marland said.

Carbon dioxide is produced when people burn fossil fuels like coal and oil for heat, power and transport. Tough curbs will require an unprecedented increase in energy efficiency and low-carbon investment, for example in nuclear and renewables, says the International Energy Agency, which advises rich states.

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Chief British government economist Nicholas Stern said in October that the world needed to cut greenhouse gas emissions by at least a quarter by mid-century, and said immediate action would be much less costly than the economic depression that would result from inaction followed by severe climate change.

The Kyoto Protocol, the only global emissions policy now in force, requires a 5 percent cut in emissions from 1990 levels by 35 countries by 2012, but does not bind three of the four biggest emitters -- the United States, which pulled out, India and China.

"If we're really going to reduce emissions it's going to take a lot more effort than is implied in the Kyoto Protocol," said Marland. "There isn't an easy way."

He submitted the CDIAC data to a US congressional committee in September but the figures remain unpublished.

One difficulty in widening the scope of the Kyoto deal has been that of persuading rapidly developing countries like China and India to shoulder targets which they fear could brake their explosive economic growth.

China could overtake the United States as the world's number one carbon emitter before 2010, but Marland reckons developed western countries face some blame as they shift manufacturing offshore to lower-cost countries.