Why International Day for Preservation of Ozone layer?

The earth’s atmosphere is conventionally divided into layers based on the average vertical variation of temperature.  Stratosphere is approximately 10 to 50 Km from the earth surface. It is characterized by a more or less continuous increase of temperature with height. The vertical increase of temperature is the result of heating by the absorption of Ultraviolet solar radiation by Ozone (O3). Ozone is produced by the photochemical dissociation of Oxygen (O2), resulting from absorption of ultraviolet solar radiation to form atoms of oxygen (O). These atoms collide with molecular oxygen (O2) to form Ozone (O3), which in term absorbs solar radiation for further dissociation to O and O2. The stratospheric ozone layer is responsible for the nearly complete absorption of solar radiation in wave lengths from 240 to 290 nanometers, thereby protecting life forms on the earth’s surface from damaging Ultraviolet (UV) radiation. In addition to its UV- absorbing properties Ozone is a greenhouse gas, absorbing outgoing infrared radiation of wavelength 9,600 nanometers and thus contributing to global warming.

It was suggested in 1974 that a group of chemicals known as chlorofluorocarbons, or CFCs, used as propellants, refrigerants, solvents and in production of foam plastics, were adding chlorine to the atmosphere and disturbing the Ozone balance. The effects of increased ultraviolet radiation include an elevated risk of skin and eye cancer in Humans and animals, and death or reduced rates of growth in plants and organisms that live near the surface in water, such as the phytoplankton that consume carbon dioxide and provide about 70% of the earth’s annual production of oxygen. Losing these could accelerate the “green effect”’ and to exacerbate the problem, CFCs are “greenhouse gases” with the same kind of effect as carbon dioxide. Increased Ultraviolet levels of the earth’s surface will have biological repercussions. Ultraviolet radiation in the wavelength band 200 to 320 nanometers (Known as UVB) is damaging to the genetic material DNA (Deoxyribonucleic Acid). Laboratory research predicted an approximate 2% increase in Melanoma risk for every 1% increase in UVB. Recognizing these dangers, in 1978 the US, Canada, Sweden and Norway banned CFCs in aerosol cans.  But still use in other and worldwide production began to increase again. Then in May 16, 1985, J.C. Farman, B.G.Gardiner, and J.D. Shanklin from the British Antarctic Survey published in the British Journal Nature an article that instantly become famous. The article reported that the total amount of ozone in the atmosphere over the observational site in Antarctica showed rapid during the Austral spring. Scientists had predicted that the injection of Chlorofluorocarbons (CFCs or ‘Freons”) into the atmosphere would gradually cause losses in Ozone over a period of decades. Thirty one nations approved a treaty in Montreal in 1987 which would reduce production of CFCs by 50% in ten years.  Later, scientists found a rapid depletion of the Ozone layer over the northern hemisphere at least three times as serious as they had expected. The treaty was amended twice to make it stricter, and DuPont, the world’s largest producer of CFCs, which had once dismissed these concerns, announced that it would cease production. In October 2000, the “ozone hole” over Antarctica extended as far north as the city of Punta Arenos, Chile.

On a global scale, determination of rates of ozone depletion is complicated by the strong modulation in total atmospheric ozone caused by the Quasi-biennial Oxillation and the 11 year solar cycle, however, recent statistical analysis of more than a decade of TOMS ozone observations suggests a global loss rate of about 0.27% per year. The dramatic destruction of Antarctic ozone and the conclusive scientific evidence pointing to man-made cause motivated precedent setting international agreements to address the problem. In 1990 the timetable was amended to eliminate all CFC emissions of industrialized countries by 2000. Observation shows a marked decrease in the growth rates of certain CFCs and Halons. Consistent with this, the abundance of substitutes (the hydrofluorocarbons and hydrochlorofluorocarbons) is increased. In the 13 Conference of Parties (CoP) in Bali, Indonesia nations decided upon a course of action called the Bali action Plan, ‘a comprehensive process to enable the full, effective and sustained implementation of the convention’.  The Bali action plan eroded thrust among developed and developing nations. As 2008 passed, the rift has grown. Age –old dissensions have come to the fore. The US is still pointing finger at China, India, Brazil and South Africa, saying if these countries do not take action, it will not. If at all the world leaders are serious about the change accruing in Ozone layer then it’s time to be serious about the way the world generates and uses its energy. Pointing fingers and shifting burdens on developing nation will not solve problems. It is time to have an effective climate agreement for the entire world.

Soyhunlo Sebu
Research Scholar
Dept. of Geography
Nagaland University
Lumami
 



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