Healing ozone layer helps prevent global warming by 0.5°C
By Freeman ya Ngulu.
The ozone layer is on track to recover within four decades, with the global phase-out of ozone-depleting chemicals already benefitting efforts to mitigate climate change. This is the conclusion of a UN-backed panel of experts, presented at the American Meteorological Society’s 103rd annual meeting. Examining novel technologies such as geoengineering for the first time, the panel warns of unintended impacts on the ozone layer.
On track to full recovery:
The Scientific Assessment Panel to the Montreal Protocol on Ozone Depleting Substances quadrennial assessment report, published every four years, confirms the phase-out of nearly 99% of banned ozone-depleting substances. The protocol has thus 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.
If substances that harm the ozone layer continue to be banned in industry, it is expected to recover to densities last measured in the 1980s, between 2040 and 2066 depending on the region.
Variations in the size of the Antarctic ozone hole, particularly between 2019 and 2021, were driven largely by meteorological conditions. Nevertheless, the Antarctic ozone hole has been slowly improving in area and depth since the year 2000.
“That ozone recovery is on track according to the latest quadrennial report is fantastic news. The impact the Montreal Protocol has had on climate change mitigation cannot be overstressed. Over the last 35 years, the Protocol has become a true champion for the environment,” said Meg Seki, Executive Secretary of the United Nations Environment Programme’s Ozone Secretariat. “The assessments and reviews undertaken by the Scientific Assessment Panel remain a vital component of the work of the Protocol that helps inform policy and decision makers.”
Impacts on climate change:
The assessment report reaffirms the positive impact that the treaty has already had for the climate. An additional 2016 agreement, known as the Kigali Amendment to the Montreal Protocol, requires a phase-down of production and consumption of many hydrofluorocarbons (HFCs). HFCs do not directly deplete ozone, but are active climate change gases. The Scientific Assessment Panel said this amendment is estimated to avoid 0.3°C to 0.5°C of warming by 2100 which does not include contributions from HFC-23 emissions.
“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,” said WMO Secretary General, Prof Petteri Taalas.
The latest assessment is based on extensive studies, research and data compiled by a large international group of experts from the World Meteorological Organization, United Nations Environment Programme, the US National Oceanic and Atmospheric Administration (NOAA), the US National Aeronautics and Space Administration (NASA) and the European Union.
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). SAI has been proposed as a possible 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.”