Climatologists say that greenhouse gas emissions, such as carbon dioxide from burning oil and coal, contribute significantly to global warming.

VOA: standard.2009.11.09

The vast majority of climate-change scientists hold that global warming is caused by burning too many fossil fuels.

ECONOMIST: Against the prevailing wind

However, the biggest single source, accounting for about half of the global total, is the most traditional - the burning of wood for heat and cooking in developing countries.

BBC: Renewables can fuel society, say world climate advisers

The World Coal Association (WCA), a trade body for the industry, said that burning coal account for about 24% of global mercury emissions and the use of "adequate technologies" could reduce emissions of the metal from coal-fired power stations by up to 90%.

BBC: Nations agree on legally binding mercury rules