"The era of sun tanning could be over," an Australian scientist has warned after a study found ozone holes over the poles have been healing but ozone levels at populated latitudes have not been recovering.
The study published on Tuesday found ozone was still decreasing between 60 degrees North and 60 degrees South, zones which take in Australia in the south and Russia in the north.
The study found the ozone holes in the upper atmosphere around Earth's poles have been healing in recent years.
The unexpected ozone decreases in part of the atmosphere may be preventing recovery at lower latitudes, said the findings published in the European Geosciences Union journal Atmospheric Chemistry and Physics.
"The finding of declining low-latitude ozone is surprising since our current best atmospheric circulation models do not predict this effect," said William Ball, the leader of the analysis.
The researchers suggest climate change may be altering the pattern of atmospheric circulation, causing more ozone to be carried away from the tropics.
The other possibility could be the presence of short-lived ozone-destroying chemicals containing chlorine and bromine, which are found in solvents, paint strippers and degreasing agents.
Ozone is a substance produced in tropical latitudes and distributed around the globe's atmosphere. It is formed in the stratosphere that is between 10 and 50 kilometres above the troposphere in which humans live.
The ozone layer absorbs much of the harmful ultraviolet radiation from the sun, which could otherwise harm plants, animals and humans.
"This study is scary. Until we understand what's really happening you'd be silly to sun yourself, except in polar regions," Bill Laurance, a professor at James Cook University in Australia, said.
"The era of suntanning could be over; we might be entering the age of the unfailing sunburn."
Scientists established in the 1970s that chemicals called CFCs (Chlorofluorocarbons) used in refrigeration, aerosols and other products, were destroying ozone in the stratosphere, with the worst effect seen in the Antarctic, where an ozone "hole" had formed.
The Montreal Protocol in 1987 led to the phase-out of CFCs. It helped the ozone layer in the Antarctic recover.
The researchers said the focus now should be on getting more precise data on the ozone decline and the causes of slowing determinants.
Ian Lowe, a professor at Griffith University, said the findings were an urgent reminder that phasing out the chemicals that weakened the ozone layer which protected all life from damaging ultra-violet radiation should be a high priority.
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