The ozone hole is shrinking. Has sunbathing become safe?

Observed today, the International Day for the Preservation of the Ozone Layer became an occasion for the release of an optimistic report. The World Meteorological Organization (WMO) reports that the ozone hole in 2024 was smaller than in previous years. What explains these positive changes?

Good news for the climate at last

On the 40th anniversary of the Vienna Convention for the Protection of the Ozone Layer, WMO published the third-ever Bulletin on ozone and UV radiation on Earth. The publication date is no coincidence – on September 16, 1987, the Montreal Protocol was signed, which became the reason for establishing the International Day for the Preservation of the Ozone Layer. Today it turns out we have something to celebrate.

According to WMO scientists, in 2024 the condition of the ozone layer around Earth was significantly better than the multi-year average from 2003–2020. Measured in Dobson units (DU), the height of the ozone column over the Arctic in March last year was even 55–60 DU higher than the average from 1960–2023. As a result, the ozone layer over the Northern Hemisphere was up to 13% denser, WMO experts emphasize.

The only two negative anomalies were observed in a limited area over Antarctica and around the southern latitude of 15°. However, it is noteworthy that the average ozone layer height for almost the entire globe (from 60°S to 60°N), the average for the Northern Hemisphere (35°N to 60°N), and the average for the tropical belt (20°S to 20°N) in 2024 reached their highest values in decades.

Why is the ozone hole disappearing?

WMO experts are convinced that the positive changes are largely the result of the active implementation of the Montreal Protocol, which eliminated the use of ozone-depleting substances, particularly CFCs, HCFCs, and methyl bromide. Over the years, a total of 160 countries joined the protocol, making it possible to achieve a real, global effect.

The ozone hole was also reduced as a result of the coincidence of several very favorable phenomena that increased the total ozone content in the atmospheric column in extratropical zones:
• The quasi-biennial oscillation (QBO) of equatorial winds was in its easterly phase.
• Strong El Niño conditions persisted in the first half of 2024.
• Planetary wave activity in the Northern Hemisphere was exceptionally high in winter and spring, which translated into increased ozone transport toward higher latitudes.
• Solar activity in 2024 remained close to its maximum, leading to increased ozone production in the upper stratosphere.
Unfortunately, the above-mentioned factors are not permanent, and their variability may cause the thickness of the ozone layer to periodically decrease again.

Skin cancer risk remains high

Does the regeneration of the ozone layer mean we can sunbathe freely, relying on its protective potential? Unfortunately not. Analysis conducted by WMO shows that the monthly amount of UV radiation over Central Europe steadily increased in 1997–2022. Scientists explain this by the decline in average cloud cover. The long-lasting drought that struck our continent in 2022 even led to a record rise in UV radiation intensity.

Protecting the skin during sun exposure remains a priority. Even more so because natural seasonal fluctuations in the thickness of the ozone layer can raise the daily UV index by as much as 10–20% in summer and up to 50% in winter.

According to the report’s authors, the risks related to solar radiation continue to grow despite successes in reducing the production and use of ozone-depleting substances. The main factor is considered to be climate change, whose impact on life on Earth never ceases to surprise.