The ozone layer is found in the stratosphere, 15-35 km above the surface of the earth. Ninety per cent of the ozone (O3) present in the atmosphere is concentrated here. Ozone is continually generated and broken down through natural processes in the stratosphere. Anthropogenic emissions of ozone-depleting substances have disturbed the balance in the stratosphere.

The ozone layer expected to recover significantly by 2050-2070

The amount of most of the ozone-depleting substances in the troposphere is now declining slowly. The ozone layer is expected to recover significantly by 2060-2075 above Antarctica and around 2050 elsewhere.

Recent global ozone data indicate that there might be signs of ozone recovery from mid 1990s in most of the world. However this is uncertain, particularly at high latitudes and in the Arctic region. The uncertainty is caused by the high natural variability in these regions, and the influence of factors like decreasing temperatures in the stratosphere, which is partly due to the increase of greenhouse gases in the troposphere.

Largest decreases in ozone concentrations over Antarctica

The largest decreases in ozone concentrations have been observed over Antarctica, particularly in September and October each year. In this so-called ozone hole, the ozone concentration is reduced by up to 60 per cent. After a couple of months new ozone is produced and the ozone layer regenerates until the next cycle starts. This phenomenon was first registered in the early 1980s.

Ozone levels over Oslo and Andøya

The Norwegian Institute for Air Research continuously monitors the ozone levels over Oslo and Andøya, on behalf of the Climate and Pollution Agency.

Depletion of the ozone layer results in higher levels of UV radiation at the earth's surface. This poses a danger to humans, animals and plants, and marine life.

Health effects

The increase in UV-B radiation associated with ozone depletion is likely to have effects on the immune system. The risk of skin cancer and infectious diseases thus increases. UV-B radiation can damage the eye's cornea, the lens and the retina. Excessive exposure to UV radiation may cause cataracts.

Ecological effects

Increasing amounts of UV radiation may have a negative impact on the production of plankton and other tiny organisms at the base of the marine food web. These organisms are the ultimate source of food for all other living organisms in the oceans. A large increase in UV radiation may also disrupt many ecosystems on land, significantly reducing yields and causing food shortages.

Damage to materials

UV radiation causes a number of materials to degrade more rapidly. In general, plastic materials used outdoors will have much shorter lifetimes.

Ozone-depleting substances such as CFCs and halons were widely used before their effect on the ozone layer was discovered. In 1986, 1.1 million tonnes of CFCs were used worldwide for many purposes; aerosols, foam-blowing agents, refrigerators, air conditioning, solvents, dry cleaning and firefighting. Ozone-depleting substances were popular because they were non-poisonous, non-flammable, cheap to produce and persistent. But it was their very stability that proved almost fatal to the earth's ozone layer.

Norway has fulfilled its obligations under the Montreal Protocol and met the EU targets for reductions in the consumption and production of ozone-depleting substances. The result is more than a 99 per cent reduction in the use of ozone-depleting substances, measured in ozone-depleting potential, since 1986.

CFCs and halons are now banned in industrialised countries but exceptions are made for CFCs used in ways that are defined as essentials; these are chemical analysis and pharmaceutical sprays such as metered dose inhalers (MDIs). Norway imported about 290 tonnes of HCFCs in 2009. Norway does not produce ozone-depleting substances.

All the countries in the world have ratified the Montreal Protocol on substances that deplete the ozone layer. The Montreal Protocol sets targets for reducing and phasing out use for each of the ozone-depleting substances.

UNEP (United Nations Environmental Programme) estimates that without the Montreal Protocol, the abundance of ozone-depleting substances in 2050 would be 5 times higher than today. Surface UV-B radiation would at least double at middle-latitudes in the Northern Hemisphere, and would be four times as intense at middle-latitudes in the Southern Hemisphere. The incidence of skin cancer would increase by several millions of cases.

Norway has met the EU targets for reduction

Norway is complying with EU targets for reducing and phasing out the use of ozone-depleting substances as stated in the regulation of 29 June 2000. The EU has been following a speedier phase-out schedule than the Montreal Protocol. Norwegian regulations implementing the EU regulations entered into force on 1 January 2003.