World Ozone Day 2020: Preservation Of Ozone
The ozone layer, a fragile shield of gas, protects the Earth from the harmful portion of the rays of the sun, thus helping preserve life on the planet.
The phaseout of controlled uses of ozone-depleting substances and the related reductions have not only helped protect the ozone layer for this and future generations but have also contributed significantly to global efforts to address climate change; furthermore, it has protected human health and ecosystems by limiting the harmful ultraviolet radiation from reaching the Earth.
Life on Earth would not be possible without sunlight. But the energy emanating from the sun would be too much for life on Earth to thrive were it not for the ozone layer. This stratospheric layer shields Earth from most of the sun’s harmful ultraviolet radiation. Sunlight makes life possible, but the ozone layer makes life as we know it possible.
So, when scientists working in the late 1970s discovered that humanity was creating a hole in this protective shield, they raised the alarm. The hole – caused by ozone-depleting gases (ODSs) used in aerosols and cooling, such as refrigerators and air-conditioners – was threatening to increase cases of skin cancer and cataracts, and damage plants, crops, and ecosystems.
The global response was decisive. In 1985, the world’s governments adopted the Vienna Convention for the Protection of the Ozone Layer. Under the Convention’s Montreal Protocol, governments, scientists and industry worked together to cut out 99 percent of all ozone-depleting substances. Thanks to the Montreal Protocol, the ozone layer is healing and expected to return to pre-1980 values by mid-century. In support of the Protocol, the Kigali Amendment, which came into force in 2019, will work towards reducing hydrofluorocarbon (HFCs), greenhouse gases with powerful climate-warming potential and damaging to the environment.
World Ozone Day, held on September 16, celebrates this achievement. It shows that collective decisions and action, guided by science, are the only way to solve major global crises. In this year of the COVID-19 pandemic that has brought such social and economic hardship, the ozone treaties’ message of working together in harmony and for the collective good is more important than ever. The slogan of the day, ‘Ozone for life’, reminds us that not only is ozone crucial for life on Earth, but that we must continue to protect the ozone layer for future generations.
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.
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 depletion is greatest at the South Pole. It occurs mainly in late winter and early spring (August-November) and peak depletion usually occurs in early October, when 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 chart below shows the development of the (annual maximum) size of the ozone hole over the Antarctic. 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.
A number of commonly used chemicals have been found to be extremely damaging to the ozone layer. Halocarbons are chemicals in which one or more carbon atoms are linked to one or more halogen atoms (fluorine, chlorine, bromine, or iodine). Halocarbons containing bromine usually have much higher ozone-depleting potential (ODP) than those containing chlorine. The man-made chemicals that have provided most of the chlorine and bromine for ozone depletion are methyl bromide, methyl chloroform, carbon tetrachloride, and families of chemicals known as halons, chlorofluorocarbons (CFCs), and hydrochlorofluorocarbons (HCFCs).
Vienna Convention for the Protection of the Ozone Layer
The scientific confirmation of the depletion of the ozone layer prompted the international community to establish a mechanism for cooperation to take action to protect the ozone layer. This was formalized in the Vienna Convention for the Protection of the Ozone Layer, which was adopted and signed by 28 countries, on 22 March 1985. In September 1987, this led to the drafting of The Montreal Protocol on Substances that Deplete the Ozone Layer.
The principal aim of the Montreal Protocol is to protect the ozone layer by taking measures to control total global production and consumption of substances that deplete it, with the ultimate objective of their elimination on the basis of developments in scientific knowledge and technological information. It is structured around several groups of ozone-depleting substances. The groups of chemicals are classified according to the chemical family and are listed in annexes to the Montreal Protocol text. The Protocol requires the control of nearly 100 chemicals, in several categories. For each group or annex of chemicals, the Treaty sets out a timetable for the phase-out of production and consumption of those substances, with the aim of eventually eliminating them completely.
The timetable set by the Protocol applies to consumption of ozone depleting substances. Consumption is defined as the quantities produced plus imported, less those quantities exported in any given year. There is also a deduction for verified destruction. Percentage reductions relate to the designated base-line year for the substance. The Protocol does not forbid the use of existing or recycled controlled substances beyond the phase-out dates.
There are a few exceptions for essential uses where no acceptable substitutes have been found, for example, in metered dose inhalers (MDI) commonly used to treat asthma and other respiratory problems or halon fire-suppression systems used in submarines and aircraft.
In 1994, the United Nations General Assembly proclaimed 16 September the International Day for the Preservation of the Ozone Layer, commemorating the date of the signing, in 1987, of the Montreal Protocol on Substances that Deplete the Ozone Layer (resolution 49/114).
Implementation of the Montreal Protocol
Implementation of the Montreal Protocol progressed well in developed and developing countries. All phase-out schedules were adhered to in most cases, some even ahead of schedule. Attention focused initially on chemicals with higher ozone-depletion potentials including CFCs and halons. The phase-out schedule for HCFCs was more relaxed due to their lower ozone-depletion potentials and because they have also been used as transitional substitutes for CFCs.
The HCFC phase-out schedule was introduced in 1992 for developed and developing countries, the latter with a freeze in 2015, and final phase-out by 2030 in developed countries and 2040 in developing countries. In 2007, Parties to the Montreal Protocol decided to accelerate the HCFC phase-out schedule for both developed and developing countries.
On 16th September 2009, the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification.
The Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer reached an agreement at their 28th Meeting of the Parties on 15 October 2016 in Kigali, Rwanda to phase-down hydrofluorocarbons (HFCs).
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.
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.
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').
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 2019.
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 area over the southern hemisphere, historically (9 September 2000) and currently (20 September 2018)