The amount of carbon locked away in frozen soils in the far Northern Hemisphere is double previous estimates and rapid melting could accelerate global warming, a study released on Wednesday says.

Large areas of northern Russia, Canada, Nordic countries and the U.S. state of Alaska have deep layers of frozen soil near the surface called permafrost.

Staples such as cassava on which millions of people depend become more toxic and produce much smaller yields in a world with higher carbon dioxide levels and more drought, Australian scientists say.

Cambodia has signed agreements for a project that aims to protect 60,000 hectares of forest and reward local communities from the sale of carbon credits over several decades, the developers said in a statement.

Within a vast deforested area on Borneo island, Australia and Indonesia hope to turn an ecological disaster into a global lesson on how to help local communities save tropical forests and fight climate change.

Tropical forests in Borneo under threat of conversion to palm oil plantations could be more profitable left standing if carbon credits were priced between $10 and $33 per tonne, a study has found.

Forests soak up vast amounts of planet-warming carbon dioxide each year and are crucial in the fight to curb climate change.

Australia's forestry firms are poised for major growth from emissions trading plans that could give the sector a multi-million dollar boost when it becomes the first to kick off a nationwide scheme to cut carbon pollution.

Australia has given UN climate talks a boost by saying it could toughen emissions targets by 2020, something developing countries want from richer nations as the world tries to seal a broader climate pact.

A study of Greenland's icesheet has revealed that a vast store of planet-warming methane appears to be more stable than thought, easing fears of a rapid rise in temperatures, a scientist said on Friday.

Residents of the Thai capital produce as much carbon pollution as New Yorkers and more than Londoners, a U.N.-backed study released on Wednesday shows.

The report, "Bangkok: Assessment Report on Climate Change 2009," underscores the city's carbon-intensive habits but also highlights the threat to Bangkok from rising seas caused by global warming.

Four of the world's top airlines have backed a global scheme to curb carbon emissions and hope the proposal will be included in a broader UN pact to fight climate change.

It is the first time airline firms have banded together to make recommendations to UN climate change officials on how to tackle the sector's carbon emissions.