Ozone Layer Recovery: A Fragile Victory (99% Progress, But Challenges Remain)

Ozone layer recovery is progressing well, thanks to the Montreal Protocol. However, new challenges arise from space activity and climate change, which could hinder future progress. Maintaining the ozone layer’s stability remains crucial for protecting Earth’s ecosystems.

CONTENTS: Ozone Layer Recovery: A Fragile Victory

Ozone Layer Recovery: A Fragile Victory

Ozone layer recovering faster than expected

In June this year, the global effort to restore and preserve the ozone layer received a significant boost when researchers confirmed a decline in the levels of ozone-depleting chemicals, specifically hydrochlorofluorocarbons (HCFCs). These substances, which include chlorine and bromine, are known to damage ozone molecules, thereby depleting the ozone layer located 15 to 35 kilometers above the Earth’s surface. The ozone layer is particularly thin over the poles, with the Antarctic stratosphere experiencing the most severe depletion, known as the “ozone hole.”

The study, led by a Bristol University scientist and published in *Nature Climate Change*, revealed promising signs of ozone recovery. For the first time since the 1970s, the research showed a reduction in the impact of HCFCs on the Earth’s energy balance and a decrease in atmospheric chlorine from these gases. Notably, this decline has occurred five years earlier than the previously projected peak year of 2026.

Ozone Layer Recovery: A Fragile Victory- In June, additional positive news emerged when a study led by researchers from the Indian Institute of Technology (IIT) Kharagpur countered earlier claims of a “severe” ozone hole in the tropical stratosphere, which had been reported in 2022. By analyzing ground-based and satellite data, the study concluded that there is no current evidence supporting the existence of an ozone hole outside Antarctica.

The recovery of the ozone layer is progressing well, thanks to the effective implementation of the Montreal Protocol, an international agreement aimed at phasing out ozone-depleting substances like HCFCs, which are mainly used in air conditioning and refrigeration. According to the UN Environment Programme (UNEP), approximately 99 percent of these harmful substances have already been phased out, and the Antarctic ozone hole could potentially disappear by the 2060s. However, maintaining this progress will likely be challenging.

Ozone Layer Recovery: A Fragile Victory- In a warming world, efforts to preserve the ozone layer face new challenges. While sectors have largely replaced ozone-depleting HCFCs and chlorofluorocarbons with hydrofluorocarbons (HFCs), which do not harm the ozone layer because they lack chlorine, HFCs contribute significantly to global warming due to their high global warming potential.

To address this issue, the 2016 Kigali Amendment to the Montreal Protocol aimed to phase out HFCs. UNEP is calling for increased action under the Kigali Amendment, highlighting its theme for World Ozone Day 2024 on September 16: “Montreal Protocol: Advancing Climate Action.” UNEP notes that if the Amendment is fully ratified and implemented, it could help avoid up to 0.5°C of warming by 2100.

Simultaneously, climate change may be affecting the stability of the ozone layer. In 2023, the Antarctic ozone hole appeared earlier in August, rather than the typical September-October timeframe, and remained until late December, as reported by the Copernicus Atmosphere Monitoring Service (CAMS).

Ozone Layer Recovery: A Fragile Victory- On December 21, 2023, an article on CAMS’ website highlighted that the Southern Hemisphere’s ozone hole has exhibited unusual behavior for the fourth consecutive year. The article, citing various research studies, attributed this trend to several factors, including the 2022 volcanic eruption in Tonga, which released large amounts of water vapor into the stratosphere. This water vapor can interact with chlorine molecules and contribute to ozone depletion.

NASA also notes that greenhouse gas emissions have a cooling effect in the upper stratosphere, which can enhance the efficiency of chlorine in destroying ozone.

A thinner ozone layer exposes the polar ecosystem and species to more ultraviolet rays, although much of this radiation is absorbed by the ice sheets. However, a study published in *Global Change Biology* in April 2024, led by a researcher from the University of Wollongong, Australia, indicated that climate change impacts in Antarctica—such as shifts in wind patterns and decreasing sea ice—might increase the exposure of organisms to ultraviolet radiation.

Ozone Layer Recovery: A Fragile Victory- In June 2024, researchers from the University of Southern California, Los Angeles, published a study in Geophysical Research Letters highlighting a new risk to the ozone layer posed by space activity. According to the study, satellites that burn up upon reentry generate aluminum oxides, which are known to act as catalysts for chlorine activation, leading to ozone depletion in the stratosphere. The research suggests that a large constellation of satellites could release up to 360 tonnes of aluminum oxides annually, potentially causing significant ozone damage.

David Fahey, co-chair of the Scientific Assessment Panel of the Montreal Protocol, was quoted in a June 24 New York Times article emphasizing the importance of this issue. Fahey, also director of the Chemical Sciences Laboratory at NOAA, noted that the Montreal Protocol will examine this concern in its next assessment in 2026.

Additionally, a UNEP report released in July, titled Navigating New Horizons—A Global Foresight Report on Planetary Health and Human Wellbeing, highlighted that increasing space activity could release gases and compounds that further deplete the ozone layer. With the global space industry projected to expand to $3.7 trillion by 2040, the report stresses the need for ongoing monitoring to ensure that the progress made in ozone protection under the Montreal Protocol is not reversed.