Ozone layer, 1980-2024

Thickness of ozone layer worldwide and above The Netherlands

Measurements show that the thickness of the ozone layer has decreased both worldwide and above the Netherlands since 1980. This is due to increasing concentrations of ozone-depleting substances in the atmosphere. The layer thinned in particular between 1980 and 1995. Since the middle of the 1990s, the thickness has remained stable at this lower level. In the period 2017–2020, the ozone layer was about 4% thinner than prior to 1980 at temperate latitudes such as the Netherlands. Ozone layer depletion is a seasonal phenomenon: in the northern hemisphere the depletion is greater in the winter and spring than in the summer and autumn.

Thickness of ozone layer above Antarctica

Since 1980, the ozone layer has become especially thinner above Antarctica, as a result of very low temperatures in the stratosphere and the formation of clouds at 20-30 km altitude. On the surfaces of the cloud droplets chemical reactions take place that cause destruction of ozone. In the month of October, when the ozone hole is largest above Antarctica, the ozone layer is 40% thinner than in October months prior to 1980. No further depletion has taken place above the South Pole since the early 1990s. The ozone layer above the South Pole was much less depleted in the autumn of 2019 than in the years before. This was due to rapid warming of the air in the stratosphere in September, which also occurred in 1988 and 2002, and is not an indication of an accelerated recovery of the ozone layer.

Thickness of ozone layer above the North Pole area

In several recent years, in which there have been cold winters in the North Pole area, the ozone layer above the North Pole has been up to about 25% thinner in the spring. The temperature in the stratosphere above the North Pole was unusually low in the spring of 2011 and again in the spring of 2020, with the result that the ozone layer was thinner than previously observed (Manney et al., 2011). In March 2024, the ozone layer over the North Pole was thicker than in the past 40 years. This was caused by unusual weather patterns that brought air with high ozone concentrations from mid-latitudes to the polar region (Newman et al., 2024). The ozone layer at the North Pole is always thicker than at the South Pole, because the supply of ozone-rich air at the North Pole is greater than at the South Pole. 

Recovery of ozone layer

The concentration of ozone-depleting substances in the stratosphere has passed its maximum level. This will allow recovery of the ozone layer to take place. While natural variability makes it difficult to detect the start of such recovery, at high altitudes in the stratosphere the onset of recovery is already observable. It is expected that the ozone layer will have recovered at mid-latitudes around 2040, above the South Pole around 2066, and above the North Pole around 2045.The increase in greenhouse gases in the atmosphere causes cooling of the stratosphere and could affect recovery of the ozone layer. The expectation, therefore, is that ozone will be broken down less rapidly in the higher stratosphere. However, uncertainties about the effect of cooling on ozone in the lower stratosphere mean that the effect on the ozone layer as a whole is yet unknown. Furthermore, the recovery of the ozone layer will be affected by the future emissions of methane and nitrous oxide. The effects of methane and nitrous oxide on the recovery of the ozone layer depends on their future emissions. Effects of methane emissions can be both positive and negative. Extra emissions of nitrous oxide have a negative effect on the thickness of the ozone layer.

Effects on humans and the environment

Due to the decrease in the amount of ozone in the stratosphere, UV radiation on earth has increased. This increase causes numerous harmful effects on health and the environment, including additional cases of skin cancer and cataract. Also it can  affect plant growth and  the lifespan of materials.

International policy: Montreal Protocol

International policies have been set up to limit or stop the production and use of substances that deplete the ozone layer. This was laid down in the Montreal Protocol of 1987. The countries that signed the protocol have committed themselves to no longer using chlorofluorocarbons (CFCs) from 1996 onwards. This obligation applies to developing countries from 2010 onwards. The protocol still allows the use of HCFCs to a limited extent until 2030. The scientific knowledge of the depletion of the ozone layer, the possible effects and the policy options are described every few years in UNEP/WMO assessment reports. The last UNEP/WMO assessment report was published in 2022.