An unexplained and unprecedented rise in carbon dioxide in the atmosphere two years running has raised fears that the world may be on the brink of runaway global warming.
Scientists are baffled why the quantity of the main greenhouse gas has leapt in a two-year period and are concerned that the Earth's natural systems are no longer able to absorb as much as in the past.
The findings will be discussed tomorrow by the government's chief scientist, Dr David King, at the annual Greenpeace business lecture.
Measurements of CO2 in the atmosphere have been continuous for almost 50 years at Mauna Loa Observatory, 12,000ft up a mountain in Hawaii, regarded as far enough away from any carbon dioxide source to be a reliable measuring point.
In recent decades CO2 increased on average by 1.5 parts per million (ppm) a year because of the amount of oil, coal and gas burnt, but has now jumped to more than 2 ppm in 2002 and 2003.
Above or below average rises in CO2 levels in the atmosphere have been explained in the past by natural events.
When the Pacific warms up during El Niño - a disruptive weather pattern caused by weakening trade winds - the amount of carbon dioxide rises dramatically because warm oceans emit CO2 rather than absorb it.
But scientists are puzzled because over the past two years, when the increases have been 2.08 ppm and 2.54 ppm respectively, there has been no El Niño.
