Scientists say ozone layer depletion has stopped
The protective ozone layer in the earth’s upper atmosphere has stopped thinning and should largely be restored by mid-century thanks to a ban on harmful chemicals, the chlorofluorocarbons (CFC) which were used in refrigerators, aerosol sprays, and some packing foams.
Ozone provides a natural protective filter against harmful ultraviolet rays from the sun, which can cause sunburn, cataracts, and skin cancer as well as damage vegetation.
First observations of a seasonal ozone hole appearing over the Antarctic occurred in the 1970s and the alarm was raised in the 1980s after it was found to be worsening under the onslaught of CFCs, prompting 196 countries to join the Montreal Protocol. “The Montreal Protocol signed in 1987 to control ozone-depleting substances is working, it has protected us from further ozone depletion over the past decades,” said Len Barrie, head of research for the World Meteorological Organization. “Global ozone, including ozone in the polar region, is no longer decreasing but not yet increasing”.
The ozone layer outside the polar regions is projected to recover to pre-1980 levels by 2048, although the annual springtime ozone hole over the Antarctic is not expected to recover until 2073.
Although CFCs have been phased out, they accumulated and persist in the atmosphere, and the effect of the ban takes years to filter through.
Scientists are still coming to grips with the complex interaction between ozone depletion and global warming, Barrie explained. “In the Antarctic, the impact of the ozone hole and the surface climate is becoming evident,” he said. “This leads to important changes in surface temperature and wind patterns, amongst other environmental changes.”
CFCs are classified among greenhouse gases that cause global warming, so the phaseout “provided substantial co-benefits by reducing climate change,” the report found. Barrie estimated that it had avoided about 10 gigatonnes of such emissions a year. However, the ozone-friendly substances that have replaced CFCs in plastics or as refrigerants - hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) — are also powerful greenhouse gases. HFCs alone are regarded as 14,000 times more powerful than carbon dioxide, which is the focus of international efforts to tackle climate change, and HFC emissions are growing by 8 percent a year, according to U.N. agencies. “This represents a further potential area for action within the overall climate change challenge,” said U.N. Environment Program chief Achim Steiner in a statement.
Source: AFP
