The recovery of the depleted ozone layer may take 5-15 years more than that estimated earlier, says a recent study. It found that the regeneration of the protective layer will be pushed back from 2044 to 2049 over the mid-latitudes (30 0 -60 0 North and South) and from 2050 to 2065 over Antarctica.
The World Meteorological Organization, a UN agency, and the United Nations Environment Programme conducted the study with the help of 250 scientists from all over the world. The same group had conducted the earlier assessment in 2002.
Thestudy says that the Antarctic ozone "hole" is expected to recur regularly for another two decades because of special conditions within the Antarctic vortex, which is a cycloneofsuper-cold,super-fastwinds.
Therecovery taking longer over the mid-latitudes is mainly due to upwardrevisionsin the amounts of ozone-depleting chlorofluorocarbons (CFCs), which are mainly used as refrigerants. CFC-11 and CFC-12 are containedinrefrigeratorsandother equipment, from which much of both typeswilleventuallybe released. CFCs have mostly been substituted by safer hydrochloroflurocarbons, but even they cause some ozone depletion.
The good news, however, is that the level of ozone-depleting substances continues to decline from its 1992-1994 peak in the troposphere and the 1990s peak in the stratosphere.