Earth’s ozone layer on way to recovery, finds UN report, should mend by 2040

A panel examining the implementation of Montreal Protocol said decline in ozone-depleting substance emissions can avoid 0.5 to 1 degrees Celsius of global warming by mid-century.

A time-lapse photo of an ozonesonde that measures the ozone layer depletion | Robert Schwarz/University of Minnesota

New Delhi: A United Nations-backed scientific panel has concluded that actions taken under the Montreal Protocol have successfully strengthened the Earth’s ozone layer, helping avoid global warming from 0.5 to 1 degrees Celsius by mid-century.

The Montreal Protocol is an 1989 international treaty aimed at regulating the production and use of chemicals that contribute to the depletion of the ozone layer.

The panel, in its assessment report, has said that a phase out of nearly 99 per cent banned ozone-depleting substances (ODS) — such as tropospheric chlorine and bromine — contributed significantly to the recovery of the ozone layer, decreasing human exposure to harmful ultraviolet (UV) rays from the sun.

While ODS significantly alter the ozone layer, three major greenhouse gases — CH4 , N2O, and CO2 — also cause changes to the dynamics of the stratosphere, thus affecting the ozone layer. These gases have increased during the industrial era and continue to rise, further influencing ozone trends in the stratosphere.

The panel noted a gradual increase in the size of the ozone hole over the Antarctic between 2019 and 2021 due to meteorological conditions like the Australian wildfires. But with continued implementation of this protocol, they noted, the Antarctic ozone layer is expected to recover to its 1980 values by 2066. The same will apply to the ozone layer over the Arctic by 2045 and across the world by 2040.

It also noted that the ozone layer in the upper stratosphere is recovering while very little signs of improvement have been seen in the lower stratosphere.

‘Reduce greenhouse gases, limit temperature increase’

The panel, consisting of a large international group of experts, including those from the World Meteorological Organization, United Nations Environment Programme, and the National Aeronautics and Space Administration, among others, presented its findings at the American Meteorological Society’s 103rd annual meeting Monday.

The report also said that the 2016 Kigali Amendment to the Montreal Protocol required phasing down production and consumption of many hydrocarbons that contribute greatly to rising temperatures and is estimated to avoid 0.3-0.5 degrees Celsius of global warming by 2100. 

Secretary-General of the World Meteorological Organization, Petteri Taalas said, “Ozone action sets a precedent for climate action. 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 panel also explored the impact of stratospheric aerosol injection (SAI), an intentional addition of aerosols into the stratosphere to reduce global warming, by increasing reflection of sun rays. This exercise helped identify and forewarn about the potential detrimental consequences, such as deepening of the Antarctic ozone hole, and delay in ozone recovery, that “could also affect stratospheric temperatures, circulation and ozone production and destruction rates and transport”.