What is the current state of the ozone layer?

Page Last modified 08 Dec 2021
7 min read
The ozone layer sits in the stratosphere between 15 km and 30 km above the earth, and shields us and other living things from the sun’s harmful ultraviolet radiation. Ozone layer depletion could have serious effects on human health and the environment.

Key messages

  • A significant reduction in the consumption of ozone-depleting substances (ODS) has been achieved globally since 1986. This reduction has largely been driven by the 1987 United Nations Environment Programme (UNEP) Montreal Protocol.
  • The largest historical extent of the ozone hole — 28.4 million square kilometres — occurred in September 2000. This area is equivalent to almost seven times the territory of the EU.
  • The 2021 ozone hole has been similar in depth and size to 2020.

Depletion of stratospheric ozone occurs over both hemispheres of the Earth. However, this phenomenon is significantly less severe in the northern hemisphere (Arctic) than in the southern hemisphere (Antarctica). This is the case because, year-to-year, meteorological variability is larger over the Arctic than over the Antarctic. Furthermore, temperatures in the stratosphere do not remain low for a long time in the Arctic as in the case in the Antarctic.

Generally, concentration levels of 220 Dobson Units (DU, marked by the thick contour in Figure 1) or less (represented in blue colours in Figure 1) are considered to show severe ozone depletion and constitute the so-called ozone hole. This is only apparent in the southern hemisphere. Here, the largest historical extent of the ozone hole - 28.4 million km2  (Figure 1 and 2) - occurred in September 2000. This area is equivalent to almost seven times the territory of the EU.

Figure 1. Maximum ozone hole extent over the southern hemisphere, from 1979 to 2021


Note: Copernicus analyses of total ozone column over the Antarctic. The blue colours indicate lowest ozone columns, while yellow and red indicate higher ozone columns. Ozone columns are commonly measured in Dobson Units. One Dobson Unit is the number of molecules of ozone that would be required to create a layer of pure ozone 0.01 millimetres thick at a temperature of 0 degrees Celsius and a pressure of 1 atmosphere. 300 DU corresponds to 3 millimetres of ozone.

Data source: Copernicus Atmosphere Monitoring Service (CAMS).

Overall, the ozone hole has shown signs of healing since 2000, which is predominantly attributable to phasing out ozone-depleting substances under the Montreal Protocol. At the same time, the extent of the ozone hole is strongly driven by stratospheric temperature, with warmer temperatures leading to a smaller ozone hole, such as in 2019 (for more information, visit the website of the Copernicus Atmosphere Monitoring Service).

However, this is not directly attributable to anthropogenic climate change, since greenhouse gases generally have a cooling effect in the stratosphere, while they contribute to global warming in the troposphere. This stratospheric cooling has a positive effect on ozone recovery with the exception of the polar regions. Here, very low temperatures can lead to an increase in the formation of polar stratospheric clouds, which facilitate ozone depletion. The ozone hole can also be periodically influenced by volcanic eruptions, increasing the stratospheric particle load and thereby depleting ozone. This partially explains those occasional years during which the ozone hole is comparatively large, e.g. in 2015 (27.9 million km²).

Figure 2. Maximum ozone hole area hole

Note: The ozone hole is a region of exceptionally depleted ozone in the stratosphere over the Antarctic. All figures are in million square kilometres.

Data source: Copernicus Atmosphere Monitoring Service (CAMS).

This year's ozone hole over the southern hemisphere showed a maximum area of 24.8 million km² in late September (Figure 2) and resembles the one from 2019 (24.0 million km2). The 2021 ozone hole has been one of the larger and deeper ones in recent years and was larger than the average over the last five and ten years (20.0 and 21.4 million km², respectively). According to researchers from the Copernicus Atmosphere Monitoring Service, colder-than-average temperatures together with strong winds in the stratosphere circling Antarctica contributed to the large 2021 ozone hole size. Ozone loss in the northern hemisphere is usually much more limited compared to the southern hemisphere. In Artic spring 2020, however, ozonesonde measurements showed ozone depletion that has been explained to occur due to unusually strong, long-lasting cold temperatures in the stratosphere.

The 2019 ozone hole has been a very small and short-lived one, which was mostly driven by special meteorological conditions. In particular, August and September 2019 showed exceptionally high temperatures in altitudes between 20 and 30 km above the ground of the Antarctic, stopping the formation of icy clouds that usually trap ozone-depleting molecules that, when released during southern hemispheric springtime, trigger ozone destruction. Taken together, the mitigation of ozone depletion is still very fragile and scientific evidence suggests that more action is still required to remove pressure on the ozone layer caused by ODS.


Ozone depleting substances © Scott Witt

Consult the EEA's latest information on ozone-depleting substances (ODS) for a complete analysis on the EU's continued progress in phasing out ODS.

Consult the EEA's online data viewer for more information and data reported by companies under the Ozone Regulation.

Browse the EEA's Climate and Energy website for more information on ozone-depleting substances.

Photo: © Arif Miletli, Sustainably Yours /EEA 

Scientific References

  • Safieddine, S., Bouillon, M., Paracho, A.‐C., Jumelet, J., Tencé, F., Pazmino, A., et al. (2020). Antarctic ozone enhancement during the 2019 sudden stratospheric warming event. Geophysical Research Letters, 47, e2020GL087810.
  • Wohltmann, I., von der Gathen, P., Lehmann, R., Maturilli, M., Deckelmann, H., Manney, G. L., et al. (2020). Near ‐ complete local reduction of Arctic stratospheric ozone by severe chemical loss in spring 2020. Geophysical Research Letters, 47, e2020GL089547.


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