The atmospheric ozone layer, which was found by scientists in the 1970s to be shrinking due to the proliferation of chlorofluorocarbons (CFCs), is on track to recover within four decades, according to an announcement this week by the UN Environment Programme (UNEP) and the World Meteorological Organization (WMO).

If current policies remain in place, the ozone layer is expected to recover to 1980 values (before the appearance of the hole in the ozone) by around 2066 over the Antarctic, by 2045 over the Arctic and by 2040 for the rest of the world, said an UN-backed panel of experts, at the American Meteorological Society’s 103rd annual meeting.

Efforts to safeguard the ozone layer by phasing out ozone-depleting CFCs and HCFCs used mainly as refrigerants began with the enactment of the Montreal Protocol on Ozone Depleting Substances by most of the world’s countries in 1987.

The UN-backed Scientific Assessment Panel to the Montreal Protocol’s quadrennial assessment report “confirms the phase out of nearly 99% of banned ozone-depleting substances has succeeded in safeguarding the ozone layer, leading to notable recovery of the ozone layer in the upper stratosphere and decreased human exposure to harmful ultraviolet (UV) rays from the sun,” said the announcement.

“That ozone recovery is on track according to the latest quadrennial report is fantastic news,” said Meg Seki, Executive Secretary of UNEP’s Ozone Secretariat.

The Montreal Protocol, by phasing out ozone-depleting gases that have a high GWP, has also aided in mitigating climate change. The 2016 Kigali Amendment to the Montreal Protocol, now ratified by 146 countries, will further contribute to mitigating climate change by phasing down HFCs.

“The impact the Montreal Protocol has had on climate change mitigation cannot be overstressed,” added Seki. “Over the last 35 years, the Protocol has become a true champion for the environment.”

The Scientific Assessment Panel said the Kigali Amendment is estimated to avoid 0.3–0.5°C (0.54–0.63°F) of warming by 2100 (this does not include contributions from HFC-23 emissions).

“Ozone action sets a precedent for climate action,” said WMO Secretary-General Prof. Petteri Taalas. “Our success in phasing out ozone-eating chemicals shows us what can and must be done – as a matter of urgency – to transition away from fossil fuels, reduce greenhouse gases and so limit temperature increase.”

The latest assessment has been made based on extensive studies, research and data compiled by a large international group of experts, including many from the WMO, UNEP, National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA) and European Commission.

Initial look at geoengineering’s impact

For the first time, the Scientific Assessment Panel examined the potential effects on ozone of the intentional addition of aerosols into the stratosphere, known as stratospheric aerosol injection (SAI), or more generally as geoengineering. SAI has been proposed as a method to reduce climate warming by increasing sunlight reflection. Yet the panel cautions that unintended consequences of SAI “could also affect stratospheric temperatures, circulation and ozone production and destruction rates and transport.”

“That ozone recovery is on track according to the latest quadrennial report is fantastic news.”

Meg Seki, Executive Secretary, UNEP’s Ozone Secretariat