In a report published in the Journal of Geophysical Research-Atmospheres, scientists say the pollutant is second only to carbon dioxide as the most powerful driver of climate change.

They add that black carbon also kills more than a million people each year who breathe it in.

Beijing is currently suffering it worst bout of hazardous air pollution on record, sending people to hospitals with respiratory problems and keeping most people indoors.

The report says tackling soot would have an almost immediate cooling effect on the planet because of the brief time it remains suspended in the atmosphere.

The researchers recommend reducing emissions from diesel engines and domestic wood and coal fires as the best way to tackle the problem.

But Piers Forster, from the University of Leeds, says that reducing greenhouse gas emissions is the only way to really ease global warming.

Photo: Steve Newman