VIEWPOINT: OUR ‘HOLE’ CONCERN
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Ozone, as we all know, is a form of oxygen present in small quantities in earth’s atmosphere and a major factor in making life on this planet possible. The earth’s atmosphere is made up of several layers. Our immediate layer is known as Troposphere where most of the weather occurs such as rain, snow and clouds. Above this layer is the Stratosphere where most of the ozone is found and the ozone layer is the region of the atmosphere from 19 to 48 kilometres above the earth’s surface. It is in this region that effects such as ozone hole band global warming originate. The ozone layer is thinnest in the Tropics (around Equator) and denser towards the poles. The amount of ozone above a point on the earth’s surface is measured in Dobson’s Units (DUs) -typically 260 Dus near the tropics and higher elsewhere. There, however are large fluctuations. It is this layer which is critically important for it protects the life on earth from the harmful effects of ultraviolet radiations from the sun; it shields the earth from 95 to 99 per cent of the ultra violet rays over exposure which causes skin cancer.
Ozone is formed in the stratosphere by the action of sunlight on ordinary oxygen present in the air of the upper atmosphere. Photochemical and electric discharges are responsible for the conversion of oxygen into ozone. The ozone layer is hot, probably 420 Centigrade as it absorbs heat from the sun and protects us from the sunlight. This action has been going on for millions of years and the nitrogen compounds in the atmosphere apparently have kept the ozone concentration at a fairly stable level. The destruction of ozone layer is supposed to cause increases in skin cancer and damage to certain crops and the marine food web.
Ironically, the presence of ozone in the lower atmosphere is harmful and it is considered a pollutant. Ozone in the lower atmosphere is formed by chemical reactions between sunlight and pollutants already in the air. A well-known example is that of chemical smog Ozone forms a part of this smog and exposure to certain concentration causes headaches, irritation of the eyes, nose, throat and respiratory tract. It can also directly damage rubber, plastic, plant and animal tissue. .
In the mid 1970’s some scientists found a decrease in ozone in the upper atmosphere and they attributed this decrease to the large scale use of chloroflurocarbons popularly known as the CFCs at that time .The CFCs are man-made chemicals used in refrigerators, air conditioners, aerosols and solvents in the production of some type of packing. The CFCs when released into the atmosphere slowly reach the upper regions The sun’s ultraviolet rays break them apart. In this process chlorine is released which reacts with ozone molecules, thereby reducing the amount of it. The destruction of ozone is estimated to be up to 100,000 per CFC molecule.
Scientists also discovered that the decrease of ozone in the upper atmosphere depends on the latitude. The decrease was found to be the strongest in the regions over the South Pole where it forms a ‘hole’. The so-called ozone hole, a thinned region of the ozone layer, develops in the Antarctic spring and continues for several months thickening again. The maximum ozone loss seems to occur during late September.
The existence of an ozone hole was first reported by research scientists from the British Antarctic Survey. It was found over Halley Bay in 1985.Ever since the ozone hole is being watched carefully every year by scientists. For the last six years the ozone hole has been seen to cover 24 million square kilometres. This year the ozone hole reveals some interesting features. Firstly, it is the smallest compared to the last four years covering almost 16 million square kilometers. Yet the scientific community feels that this loss is considerable. The second unusual occurrence is that the ozone hole has split into two lobes instead of staying in one blob generally centered over Antarctica. This does not mean that the ozone depletion activities have decreased, says NASA scientist Newmann. According to him it is due to weird weather conditions.
The initial findings regarding the decrease of ozone layer was surprising to the scientists and they started doubting their own instruments. In 1986 a Ozone Trend Panel was set by NASA together with such organizations as World Meteorological Organization(WMO) and United Nations Environment Programmed (UNEP). To study ozone depletion in the atmosphere, extensive data were collected using weather satellites and other ground instruments. The members of the panel confirmed in March 1988 that the ozone layer was decreasing. Similarly, Germany and France launched a project called Chemistry of Ozone in the Polar Stratosphere (CHEOPS) to study ozone depletion in the northern regions. These studies showed that the Arctic region was also experiencing a similar problem. The (WMO) observed a 45 per cent depletion of ozone layer over one third of northern hemisphere from Greenland to Siberia for several days during the winter of 1995-1996.
While scientists were studying the upper atmosphere, actions were initiated at global level to tackle the problem of ozone depletion, In 1985 the Vienna Convention for the Protection of the Ozone Layer outlined the responsibilities for protecting human health and environment against the effects of depletion.
The next landmark development was the Montreal Protocol. The Treaty was originally signed in 1987 and subsequently amended in 1990 and 1992 as our scientific knowledge about ozone chemistry grew. This is the first global agreement in which nations agreed to restrict the production of CFCs. The Treaty took effect on January1,1989 when it was ratified by 36 nations including the United States of America. The Montreal Protocol stipulated that the production and consumption of compounds that delete ozone in the stratosphere- the CFCs, the halons, carbon tetra chloride and choloroform- are to be phased out by 2000. Consequent upon this the production of CFCs in the developed countries ceased by 1995 and the developing countries agreed to phase it out by 2010.
In 1990 a re- evaluation of the Montreal protocol established that though the production of CFCs has slowed down, the substitutes introduced in their place were also harmful to the ozone layer especially the Hydrochloroflurocarbons (HCFCs). The countries have now agreed to phase out these also- the developed countries by 2030 and the developing countries by 2010. Recognizing their responsibilities countries of the European Community are leading the movement by imposing stricter measures in the control of CFCs and other compounds. The developing countries including India are willing participants in these efforts.
India being a signatory to the Montreal Protocol, created a ‘Ozone Cell’ in the Ministry of Environment and Forests on April 1, 1993. It deals with all works relating to the Vienna Convention for the Protection of the Ozone Layer and Montreal Convention for phasing out the ozone depleting substances (ODS).