China 'now top carbon polluter'

China has already overtaken the US as the world's "biggest polluter", a report to be published next month says.

The research suggests the country's greenhouse gas emissions have been underestimated, and probably passed those of the US in 2006-2007.

They warn that unchecked future growth will dwarf any emissions cuts made by rich nations under the Kyoto Protocol.

Video showing the extent of China's smog problem