By Irina Petropavlovskikh, Secretary of the International Ozone Commission and a CIRES and NOAA scientist
September 16 is the International Day for the Preservation of the Ozone Layer, celebrating the anniversary of the 1987 signing of the Montreal Protocol on Substances that Deplete the Ozone Layer. The Montreal Protocol is the globally ratified treaty that controls the production and consumption of ozone depleting substances (ODSs) and many replacements for these substances.
The theme of this year’s International Day for the Preservation of the Ozone Layer is: “Montreal Protocol: fixing the ozone layer and mitigating climate change,” highlighting the projected impact of the Protocol on climate change in phasing down hydrofluorocarbons (HFCs)—which are ODSs and potent greenhouse gasses—through the Kigali Amendment to the Montreal Protocol, and the adoption of green cooling technologies.
The International Ozone Commission reports milestones and successes in the progress toward ozone layer recovery. This year, those include:
The Antarctic ozone hole reappeared in 2023. The ozone hole has occurred every year since the early 1980s, caused by human-produced and long-lived ODSs in our atmosphere. The ozone hole has shown a slight improvement over the last decade, consistent with theory and model simulations with declining levels of ODSs.
Atmospheric ODS concentrations are decreasing, but are still at levels that can cause significant polar spring-time ozone destruction. Because of the Montreal Protocol, this decrease in ODSs is causing the Antarctic ozone hole and worldwide ozone depletion to slowly decrease. The ozone hole is projected to return to 1980 levels in the 2060-2070 period.
The January 2022 Hunga Tonga-Hunga Ha’apai (HTHH) volcanic eruption injected an unprecedented amount of water vapor into the stratosphere, on top of volcanic aerosols. This water vapor plume was carried into the Antarctic vortex in early spring 2023 (as seen by the NASA Aura satellite’s Microwave Limb Sounder), and this may have an impact on the 2023 ozone hole. The HTHH volcanic eruption illustrates that the ozone hole’s year-to-year variability can be enhanced by unexpected events.
Arctic ozone depletion is generally much weaker than its Antarctic counterpart, and it was again moderate in the spring of 2023. Arctic ozone depletion is typically caused by a combination of factors that result in strong polar vortices especially through March and unusually weak dynamical processes over the winter. Typically, these processes drive movements of ozone-rich air through the polar vortex.
Our ability to monitor and understand ozone and the stratosphere is crucially dependent on satellite, balloon, and ground-based ozone observing systems. The coming demise of long-term satellites (e.g., NASA’s Aura, Aqua, and Terra) will limit scientific monitoring of both ozone layer health and levels of anthropogenically produced ODSs. The large variability of Antarctic and Arctic ozone depletion in recent years; the significant impact that the HTHH eruption is having on climate, ozone, and the stratosphere; and the recent findings of unexpected CFC-11 emissions demonstrate the need for and importance of continuous monitoring of the ozone layer and ozone depleting substances to assess global compliance to the Montreal Protocol.
The Montreal Protocol is a binding, pioneering agreement that solved a global atmospheric pollution problem. Our scientific understanding of ozone depletion since the signing of the Montreal Protocol has enabled policies that control ODS consumption and production. The Protocol provides a successful blueprint for development of global science policy dialogue on environmental issues.
This post is adapted from the September 16 press release from the International Ozone Commission. Read the full IO3C press release here.
For the current state of the ozone layer at the South Pole and to learn what happens to ozone during the Antarctic spring ozone season, follow this blog and visit NOAA’s South Pole Ozone Hole webpage.
