They see planting trees as a partial alternative to cutting emissions of the gas from power stations and vehicle exhausts. Peter Cox of the Hadley Centre, part of Britain's Meteorological Office, shares the UN panel's conclusions. The result will be no overall reduction in CO2 levels. The US Environmental Protection Agency would not comment when approached by New Scientist. But other governments are concerned.
Sinks are much less secure than carbon in fossil fuels left unburnt.
The discovery that forests are not a panacea for global warming only emerged after they were given a central role in the Kyoto Protocol, the treaty signed two years ago by most of the world's governments in a bid to stem the greenhouse effect. The first public warning came in the March issue of the IGBP newsletter. And this month, the IPCC incorporated its analysis into a forthcoming report on land use change and forestry. Each year, CO2 emissions from human activity pour just over 6 billion tonnes of carbon into the atmosphere. Around a third is absorbed by the world's forests.