DESPITE efforts to phase-out ozone depleting gases like CFCs and HCFCs, depletion of the ozone layer over the Arctic has reached an unprecedented level this spring, according to the UN's World Meteorological Organisation.
Very low winter temperatures in the stratosphere combined with the continuing presence of long-lifetime ozone-depleting substances in the atmosphere are blamed.

The Arctic region is said to have suffered an ozone column loss of about 40 per cent from the beginning of the winter to late March. The highest ozone loss previously recorded was about 30 per cent over the entire winter.

At the opposite end of the Earth, the so-called Antarctic ozone hole is an annually recurring winter/spring phenomenon due to the existence of extremely low temperatures in the stratosphere. In the Arctic the meteorological conditions vary much more from one year to the next and the temperatures are always warmer than over Antarctica. Hence, some Arctic winters experience almost no ozone loss, whereas cold stratospheric temperatures in the Arctic lasting beyond the polar night can occasionally lead to substantial ozone loss.

Even though this Arctic winter was warmer than average at ground level, it was colder in the stratosphere than for a normal Arctic winter.

Thanks to the Montreal Protocol, the ozone layer outside the polar regions is projected to recover to its pre-1980 levels around 2030-2040 according to the WMO/UNEP. In contrast, the springtime ozone layer over the Antarctic is expected to recover around 2045-60, and in the Arctic it will probably recover one or two decades earlier.