In 2014, the level of these substances had declined by about nine per cent from the record maximum in 2000.
But scientists are working to determine whether the reduction in the hole’s size is a result of the reduction in chlorine or temperature increases, which would also decrease its size.
Paul Newman, the chief scientist for atmosphere at NASA’s Goddard Space Flight Centre, said: “Year-to-year weather variability significantly impacts Antarctica ozone because warmer stratospheric temperatures can reduce ozone depletion.
“The ozone hole area is smaller than what we saw in the late-1990s and early 2000s, and we know that chlorine levels are decreasing.
“However, we are still uncertain about whether a long-term Antarctic stratospheric temperature warming might be reducing this ozone depletion.”
The minimum thickness of ozone layer this year was recorded at 114 Dobson units, equating to about one millimetre, on 30 September, compared to 250-350 Dobson units during the 1960s.
Article Appeared @http://www.independent.co.uk/news/science/hole-in-ozone-layer-above-antarctica-reaches-size-of-north-america-9833341.html