THE rising demand for flat-screen televisions may have a greater impact on global warming than the world's largest coal-fired power stations, a leading environmental scientist has warned.

Manufacturers use a greenhouse gas called nitrogen trifluoride to make the televisions. As the sets have become more popular, annual production of the gas has risen to about 4000 tonnes.

As a driver of global warming, nitrogen trifluoride is 17,000 times more potent than carbon dioxide, yet no one knows how much of it is being released into the atmosphere by the industry, said Michael Prather, director of the environment institute at the University of California.