Ozone layer - Preserving a protector of life

By Pramod DE SILVA

20th anniversary of Montreal protocol

On December 19, 1994, the United Nations General Assembly proclaimed September 16 as the International Day for the Preservation of the Ozone Layer. This commemorates the date, in 1987, on which the Montreal Protocol on Substances that Deplete the Ozone Layer was signed. The Protocol came into effect in 1989.

But just what is the Ozone layer and why is it important? Ozone is a special form of Oxygen made up of three oxygen atoms rather than the usual two oxygen atoms. The ozone layer is a deep layer in the stratosphere encircling the Earth that has large amounts of ozone. The layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun.

It is also this ultraviolet radiation that forms the ozone in the first place. It usually forms when some type of radiation or electrical discharge separates the two atoms in an oxygen molecule (O2), which can then individually recombine with other oxygen molecules to form ozone (O3).

The ozone layer became more widely appreciated when it was realised that certain chemicals mankind manufactures, called chlorofluorocarbons find their way up into the stratosphere where, through a complex series of chemical reactions, they destroy some of the ozone. As a result of this discovery, an international treaty was signed and the manufacture of these chemicals was stopped. The ozone layer has since begun to recover as a result of these efforts. Full recovery is expected by 2050.

Vital part of planet

The ozone layer is thus a very important part of our planet and a natural mechanism to shield us and the ecosystem from the dangers posed by the Sun, which also gives us life. The depletion of the ozone layer has led to serious health risks for the Earth's population.

The ozone hole

The Montreal Protocol and other treaties liberate us from a number of man-made chemicals that have threatened life on Earth: chlorofluorocarbons (CFCs) and halons among others. This year is especially significant in terms of protecting the ozone layer because no new production of CFCs is allowed from January 1. The phasing out of existing products (those manufactured before 2010) is expected to be completed by 2030. Alternatives have been developed for these substances often used in air-conditioning and refrigeration, agriculture, energy generation, medicine and precision laboratory measurements. Since the Montreal Protocol came into effect, the atmospheric concentrations of the most important chlorofluorocarbons and related chlorinated hydrocarbons have decreased. This is a landmark achievement in a world that is often divided on many issues of critical importance, from disarmament to trade. The Montreal Protocol has been a resounding success due to its widespread adoption and implementation. It has been hailed as an example of exceptional international co-operation with the former UN Secretary General Kofi Annan quoted as saying that "perhaps the single most successful international agreement to date has been the Montreal Protocol". It has been ratified by 196 states including Sri Lanka which is well on track to meet all Ozone and climate change goals.

There is also a Multilateral Fund for the Implementation of the Montreal Protocol that provides funds to help developing countries such as Sri Lanka to phase out the use of ozone-depleting substances. The fund is replenished on a three-year basis by the donors. The funds are used to finance the conversion of existing manufacturing processes, train personnel, pay royalties and patent rights on new technologies, and establish national ozone offices.

Protocol signed

The Protocol was signed "recognising that worldwide emissions of certain substances can significantly deplete and otherwise modify the ozone layer in a manner that is likely to result in adverse effects on human health and the environment" . The signatory States were "determined to protect the ozone layer by taking precautionary measures to control equitably total global emissions of substances that deplete it, with the ultimate objective of their elimination on the basis of developments in scientific knowledge".

It would be futile to treat climate change and the depletion of the ozone layer separately. The emission of greenhouse gases especially in developed countries has led to temperature changes and coupled with ozone depletion, the result would have been disastrous. Now the world is acting fast to reverse both these dangers. The ozone program has been a success, and the other too can be a success with international cooperation.

The effects of CFCs on the upper atmosphere were first discovered in 1973 by Frank Sherwood and Mario Molina at the University of California, Irving. They discovered that CFC molecules were stable enough to remain in the atmosphere until they got up into the middle of the stratosphere where they would finally (after an average of 50-100 years for two common CFCs) be broken down by ultraviolet radiation, releasing a chlorine atom.

The ozone layer protects our Earth

Rowland and Molina suggested that these chlorine atoms might cause the breakdown of large amounts of ozone in the stratosphere. Molina and Rowland were awarded the 1995 Nobel Prize for Chemistry for their discovery.

They found that since stratospheric ozone absorbs most of the ultraviolet-B (UV-B) radiation reaching the surface of the planet, depletion of the ozone layer by CFCs would lead to an increase in UV-B radiation at the surface, resulting in an increase in skin cancer and other impacts such as damage to crops and to marine phytoplankton. Of course, the Rowland-Molina theory was disputed by representatives of the aerosol and halocarbon industries. But later tests, and the discovery of the famous polar "Ozone Hole" in 1985 showed that their theory was correct. This discovery was made by British Antarctic Survey scientists, who published their research in the journal Nature.

The good news is that the work of these pioneers was not in vain. The most recent (2006) scientific evaluation of the effects of the Montreal Protocol states, "The Montreal Protocol is working: There is clear evidence of a decrease in the atmospheric burden of ozone-depleting substances and some early signs of stratospheric ozone recovery."

This is indeed a major success story in international North-South cooperation, but the world community should not let their guard down in the face of environmental dangers. The Earth is our Home, and protecting it is the responsibility of one and all.