However, Adrian McDonald at New Zealand's University of Canterbury said, it is difficult to determine when the ozone might return to natural levels, because of the complexity of interactions between greenhouse gases in the atmosphere.
"Ozone levels above Antarctica are projected to return to 1980 levels (previous to the ozone hole) after 2050," McDonald, from the university's astronomy and physics department, said. "The Montreal Protocol means that emissions of ozone depleting substances (CFCs) have largely been banned worldwide."
The use of CFCs, once widely found in common household items such as refrigerators and aerosol sprays, was curbed under the Montreal Protocol agreed by the international community in 1987.
The ozone layer, about 15 miles high in the stratosphere, acts as a filter protecting life on Earth from ultraviolet solar radiation. Its depletion over Antarctica has been a concern in Southern Hemisphere countries such as New Zealand, China's official Xinhua news agency reported.
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