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Climate Action

Protecting the ozone layer


World governments agreed in the late 1980s to protect the Earth’s ozone layer by phasing out ozone-depleting substances emitted by human activities, under the Montreal Protocol. In Europe, the Protocol is implemented through EU-wide legislation that not only meets its objectives but also contains stricter, more ambitious measures.

Global action taken under the Montreal Protocol has halted the depletion of the ozone layer and allowed it to start recovering, but much remains to be done to ensure a steady recovery.

The ozone layer

The ozone layer is a natural layer of gas in the upper atmosphere that protects humans and other living things from harmful ultraviolet (UV) radiation from the sun.

Although ozone is present in small concentrations throughout the atmosphere, most (around 90%) exists in the stratosphere, a layer 10 to 50 kilometres above the Earth’s surface. The ozone layer filters out most of the sun's harmful UV radiation and is therefore crucial to life on Earth.

Ozone depletion

Scientists discovered in the 1970s that the ozone layer was being depleted.

Atmospheric concentrations of ozone vary naturally depending on temperature, weather, latitude and altitude, while substances ejected by natural events such as volcanic eruptions can also affect ozone levels.

However, these natural phenomena could not explain the levels of depletion observed and scientific evidence revealed that certain man-made chemicals were the cause. These ozone-depleting substances were mostly introduced in the 1970s in a wide range of industrial and consumer applications, mainly refrigerators, air conditioners and fire extinguishers.

Ozone hole

Ozone depletion is greatest at the South Pole. It occurs mainly in late winter and early spring (which is from August to November in that region) and peak depletion usually occurs in early October, when the ozone is often completely destroyed in large areas.

This severe depletion creates the so-called “ozone hole” that can be seen in images of Antarctic ozone, made using satellite observations. In most years, the maximum area of the hole is bigger than the Antarctic continent itself. Although ozone losses are less radical in the Northern Hemisphere, significant thinning of the ozone layer is also observed over the Arctic and even over continental Europe.

Most of the ozone-depleting substances emitted by human activities remain in the stratosphere for decades, meaning that ozone layer recovery is a very slow, long process. The hole grew in the years following ratification of the Montreal Protocol, due to the lag caused by the fact that ozone-depleting substances remain in the stratosphere for a long time. The maximum size of the ozone hole is now decreasing.

For the status of the currently ongoing ozone hole, you can visit the Copernicus web site

Effects of ozone depletion for humans and the environment

Ozone layer depletion causes increased UV radiation levels at the Earth's surface, which is damaging to human health.

Negative effects include increases in certain types of skin cancers, eye cataracts and immune deficiency disorders. UV radiation also affects terrestrial and aquatic ecosystems, altering growth, food chains and biochemical cycles. Aquatic life just below the water’s surface, the basis of the food chain, is particularly adversely affected by high UV levels. UV rays also affect plant growth, reducing agricultural productivity.

Action to protect the ozone layer

The Montreal Protocol

In 1987, to address the destruction of the ozone layer, the international community established the Montreal Protocol on ozone-depleting substances. It was the first international treaty to be signed by all countries of the world and is considered the greatest environmental success story in the history of the United Nations.

The Montreal Protocol’s objective is to cut down the production and consumption of ozone-depleting substances, in order to reduce their presence in the atmosphere and thus protect the Earth's ozone layer.

The chart below shows the decreasing consumption of ozone-depleting substances covered by the Montreal Protocol.

Consumption of controlled ozone-depleting substances (ODS) (EU-27 and global level)
Consumption of controlled ozone-depleting substances (ODS) (EU-27 + UK and global level)
European Environment Agency

Source: European Environment Agency

EU regulation

EU legislation on ozone-depleting substances is among the strictest and most advanced in the world. Through a series of regulations, the EU has not only implemented the Montreal Protocol but has often phased out dangerous substances faster than required.

The current EU ‘Ozone Regulation’ (Regulation (EC) 1005/2009) contains a number of measures to ensure a higher level of ambition. While the Montreal Protocol regulates the production of these substances and their trade in bulk, the Ozone Regulation prohibits their use in most cases (certain uses are still permitted in the EU). Moreover, it regulates not only substances in bulk, but also those contained in products and equipment.

The EU Ozone Regulation also sets licensing requirements for all exports and imports of ozone-depleting substances and regulates and monitors not only substances covered by the Montreal Protocol (over 90 chemicals), but also some that are not covered (five additional chemicals called 'new substances').

For further details, see the Ozone Regulation section.

Impact of global action & remaining challenges

Global consumption of ozone-depleting substances has been reduced by some 98% since countries began taking action under the Montreal Protocol. As a result, the atmospheric concentration of the most aggressive types of ozone-depleting substances is falling and the ozone layer is showing the first signs of recovery.

Nevertheless, the ozone layer is not expected to recover fully before the second half of this century. This is because once released, ozone-depleting substances stay in the atmosphere for many years and continue to cause damage.

Much remains to be done to ensure the continued recovery of the ozone layer and to reduce the impact of ozone-depleting substances on the Earth’s climate.

Maximum ozone hole extent over the southern hemisphere, from 1979 to 2022.

The images below show analyses of total ozone over the Antarctic by Copernicus. The blue colours indicate the lowest ozone amounts, while yellow and red indicate higher ozone amounts.

Maximum ozone hole extent over the southern hemisphere, from 1979 to 2022
Maximum ozone hole extent over the southern hemisphere, from 1979 to 2022

Source: European Environment Agency

Actions required globally to continue the recovery of the ozone layer are:

  • Ensuring that existing restrictions on ozone-depleting substances are properly implemented and global use of ozone-depleting substances continue to be reduced.
  • Ensuring that banks of ozone-depleting substances (both in storage and contained in existing equipment) are dealt with in an environmentally-friendly manner and are replaced with climate-friendly alternatives.
  • Ensuring that permitted uses of ozone-depleting substances are not diverted to illegal uses.
  • Reducing use of ozone-depleting substances in applications that are not considered as consumption under the Montreal Protocol.
  • Ensuring that no new chemicals or technologies emerge that could pose new threats to the ozone layer (e.g. very short-lived substances).

Relationship between ozone-depleting substances & climate change

Most man-made ozone-depleting substances are also potent greenhouse gases. Some of them have a global warming effect up to 14000 times stronger than carbon dioxide (CO2), the main greenhouse gas.

Therefore, the global phase-out of ozone depleting substances such as hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) has also made a significant positive contribution to the fight against climate change.

On the other hand, the global phase-out has led to a large increase in the use of other types of gases, to replace ozone depleting substances in various applications. These fluorinated gases (‘F-gases’) do not damage the ozone layer, but do have a significant global warming effect. Therefore, in 2016, Parties to the Montreal Protocol agreed to add the most common type of F-gas, hydrofluorocarbons (HFCs), to the list of controlled substances.

For more information, see the Fluorinated greenhouse gases section.


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