The results have potential implications for the Kyoto Protocol negotiations where recent difficulties have included a lack of scientific knowledge about the strength and distribution of carbon sinks and how they vary from year to year.
Produced by a team of 30 leading carbon scientists from around the world, the paper draws on a large body of research to build up a new and comprehensive picture of carbon sinks on land.
"It is a major step forward in understanding where terrestrial carbon sinks actually are, why they are there, and how long they will operate into the future," said Dr Will Steffen, one of the authors and Executive Director of the International Geosphere-Biosphere Programme (IGBP), which coordinated the production of the paper.
The report states that carbon sinks of todays magnitude cannot be relied on to operate steadily into the future because the key processes that give rise to the sinks in the first place are temporary and likely to diminish with time.
"Although carbon sinks have a role to play in absorbing excess carbon dioxide, it is possible that the net global terrestrial carbon sink may disappear altogether in the future," said lead author Professor David Schimel from the Max Planck Institute for Biogeochemistry in Jena, Germany.
One of the key points of the report is that a large part of the current Northern Hemispheric sink is likely to have been caused by relatively recent changes in land use and land management. For example, the North American carbon sink is thought to be primarily the result of forest regrowth after the abandonment of agricultural land during the 1980s and 1990s together with a reduction in the frequency of wild fires. In China and Europe, carbon sinks a
Contact: Susannah Eliott
International Geosphere-Biosphere Programme