Earth's ozone layer as seen from space

The thinning of the ozone layer

Ozone is a form of oxygen with three atoms instead of the normal two. It forms a fragile shield in the stratosphere that absorbs the sun's ultraviolet radiation away from the earth's surface. It forms a layer 3 mm thick, but if it disappears or thins, all life on Earth will be annihilated.

Near the earth's surface, ozone is an increasingly troublesome pollutant, but safely at a height of 20-30 km from the earth in the atmosphere, it is as important to life as oxygen itself.

Global concern

The thinning of the ozone layer has been a global concern over the past decade. This is due to several chemical pollutants released by industries or produced by other chemical reactions. Chlorofluorocarbons (CFCs) are inert, inexpensive, stable, non-flammable, non-toxic substances that are easy to store and produce. The population explosion is one of the causes of the increase in CFCs due to the use of air conditioners, insulation, solvents and fire-fighting products.

In 1986, three US agencies, the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA) and the Federal Aviation Administration (FAA) began reporting ground and satellite data on ozone depletion in the stratosphere by chemicals such as Halon 1301, methyl, chloroform, carbon tetrachloride, FC-113 solvents, CFC-11 aerosols, foams and refrigeration, and CFC-12 air conditioning that deplete the ozone layer by 4, 5, 8, 12 and 26 per cent, respectively, on a global scale due to human activities.

In terms of CFC consumption, the USA leads with 29 %, followed by Russia and Europe with 14 %, while China and India consume only 2 %. Total ozone amounts in the northern hemisphere at mid and high latitudes have been decreasing, with sudden and unexpected decreases in the Antarctic zone in spring confirmed over 15-20 km in the stratospheric ozone layer.

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What will be the consequences if the ozone layer is depleted?

Increased ozone depletion will invite deadly ultraviolet rays from the sun that will cause cancer, eye damage, harm plants and marine life and even reduce our immunity to disease. UV-B damages the genetic material of DNA and also causes skin cancer. Ultraviolet rays even reduce the effectiveness of the immune system, thus impairing the body's resistance.

Experts believe that the animal and plant world will face a major challenge if radiation is not controlled. Some crops have been shown to be vulnerable to this radiation. Under the impact of radiation, proteins in plants, microbes and animals would be affected and these changes in spatial orientation would be critical in the formed part of the reaction centre of an enzyme.

Near cities with higher population concentrations, ozone could form near the earth's surface, with disastrous effects on human health, crops and ecosystems. It would also increase the incidence of smog in areas of industrial concentration. Ozone has had an effect on the earth's climate by adding to the greenhouse effect.

The world is now very concerned about the most dramatic evidence of ozone layer depletion - a 'hole' in the ozone layerwhich appears every spring over Antarctica.

Nat Geo France | Science: The protective role of the ozone layer.

Measures taken to protect the ozone layer

As this is a serious problem, it is the duty of the developed countries, which have both the technology and the infrastructure, to combat ozone depletion. Also, as it is not a problem of individual nations, combined efforts can only stop it.

Concerns about protecting the ozone layer began in the late 1970s and early 1980s. In 1978, the United States banned major CFCs for most uses; in 1980, European Community countries limited CFC production and reduced their use in aerosol products by 30 %. Sweden, Norway and Canada have also restricted the use of CFCs. In 1975, UNEP also expressed serious concern about the depletion of the ozone layer and developed a Global Plan of Action for the Ozone Layer.

Some of the important international measures taken for the protection of ozone are listed below:

  • 1977: Creation of the UNEP Coordinating Committee on the Ozone Layer.
  • 1985: Vienna Convention for the Protection of the Ozone Layer.
  • 1987: Montreal Protocol on substances that deplete the ozone layer.
  • 1988: Entry into force of the Vienna Convention.
  • 1989: Entry into force of the Montreal Protocol.
  • 1990: Amendment of the Montreal Protocol in London. The amendment obliges signatory governments to regulate the consumption and production of CFCs.
  • 1992: 112 States ratified the Montreal Protocol