The ozone layer is no longer disappearing and could be back to full strength by the middle of this century, UN scientists have confirmed.
The phasing out of nearly 100 substances once used in products like refrigerators and aerosols has stopped the ozone layer being depleted further, although it is not yet increasing, according to a new United Nations report released last week.
And it claimed that international efforts to protect the ozone layer has averted millions of cases of skin cancer worldwide.
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.
Ozone in the stratosphere is important because it absorbs some of the Sun’s dangerous ultraviolet radiation.
They say that phasing out almost 100 substances once used in such products as refrigerators and aerosols has stopped the layer from further depletion.
Ozone in the stratosphere is important because it absorbs most of the sun’s dangerous ultraviolet radiation, which can lead to skin cancer and eye damage.
The United Nations report, Scientific Assessment Of Ozone Depletion 2010, paints a much more optimistic picture than previous assessments and is the first comprehensive update in four years.
It argues that action taken through the Montreal Protocol, which began in 1987 and has introduced the reduction of harmful emissions, has helped to halt the damage.
Achim Steiner, UN under-secretary general and environmental programme executive director, said: “Without the Protocol, levels of ozone-depleting substances could have increased tenfold by 2050.
“This, in turn, could have led to up to 20 million more cases of skin cancer and 130 million more cases of eye cataracts, not to speak of the damage to human immune systems, wildlife and agriculture.”
News that the protective layer in the earth’s upper atmosphere has stopped thinning was widely welcomed last night.
Although CFCs have been phased out, they accumulated and persist in the atmosphere and the effect of the curbs takes years to filter through.
The ozone hole over the South Pole, which varies in size and is closely monitored when it appears in springtime each year, is likely to persist even longer and may even be aggravated by climate change, the report said.
Scientists are still getting 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,” Barrie added.
CFCs are classified among greenhouse gases that cause global warming, so the phase out “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 (CO2), which is the focus of international efforts to tackle climate change, and HFC emissions are growing by eight percent a year, according to UN agencies.