The impact of black carbon, emitted by aeroplanes, on monsoon, glaciers and ozone layer is "uncertain", but its sustained emission could lead to warming of the atmosphere at 10-12 km altitude, the government said today. Minister of State for Environment Mahesh Sharma informed the Rajya Sabha that studies have shown that black carbon emitted by aeroplanes can reach the stratosphere. "As per information provided by the Department of Science and Technology, aeroplanes emit black carbon into the atmosphere. Sustained emission of black carbon from aeroplanes may create a layer of black carbon at around 10 to 12 km altitude and could warm the atmosphere at that level," he said. "However, the impact of black carbon on monsoon, glaciers and ozone layer is quite uncertain," Sharma said. He said there have been laboratory experiments which showed that black carbon can act as a neutral surface for ozone depleting reactions. "However, high altitude balloon experiments simultaneous with modelling studies at Indian Institute of Science have shown that black carbon emitted by aeroplanes can reach the stratosphere," the minister said. He was replying to the question whether aeroplanes may be emitting significant amounts of black carbon, upsetting the monsoon, quickening glacier melt and depleting ozone layer and whether for the first time, it has been shown that black carbon from aircraft can go to the stratosphere and affect the ozone layer.