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There are four imperative layers in our biosphere: troposphere, stratosphere, mesosphere and thermosphere. Out of these four, stratosphere is a very important zone as it carries ozone (O3). Ozone, a three-atom isotope is an unstable gas. It is formed and disintegrated by natural processes.
Ozone absorbs ultraviolet solar radiation and saves the earth's surface from becoming too hot. Ozone layer in the lower atmosphere (lower stratosphere) is a life saving and protective layer for all biota in the biosphere. As a matter of fact, ozone layer is like an umbrella which protects all forms of life on earth from ultraviolet radiation.
But due to the internal activities of the earth, industrialization, deforestation, production and use of atomic and chemical weapons, excessive use of agrochemicals, production and use of luxurious products and variation of the density of the sunlight etc., ozone layer is now under threat.
Creation and depletion of ozone are natural processes which operate continuously in nature. But ozone depletion by anthropogenic factors is a serious environmental problem as man-induced ozone depletion cannot be automatically reversed unless preventive measures are taken in time.
The release of CFC's (chlorofluorocarbons) from specific appliances like air conditioners, refrigerators, hair dryers, fire extinguishers etc. break the ozone layer (O3gO2+O) and cause ozone depletion that enables more solar ultraviolet rays to reach the earth's surface and increase air temperature.
Besides, green house gases are detrimental to ozone layer. The gases with the properties of greenhouse are called green house gases—a combination of carbon dioxide (CO2), nitrogen oxides (NO, NO2), methane (CH4), water vapour (H2O) etc. CO2 is considered the most hazardous of green house gases which is guilty of global warming. The emissions of carbon dioxide from anthropogenic sources - burning of coal and wood, mineral oil etc. are rapidly increasing nowadays.
According to Intergovernmental Panel on Climate Change (IPCC) report on climate change (2001), the carbon dioxide concentration in 1988 was 350-360 ppm and it would be 405-560 ppm in 2025, 445-640ppm in 2050 and 540-970 ppm in 2100. Mean global temperature would be 0.4-1.10c by 2025, 0.8-2.60c within 2050 and 1.4-5.80c by 2100. In addition, global mean sea level will also rise 3-14 cm by 2025, 5-32 cm by 2050 and 9-88 cm by 2100.
Statistics shows, environmental insurgencies—fast rate of melting of Greenland ice sheets, warming of ocean water at global level, gradual rise of sea level, escalation of tropical diseases towards temperate and polar regions, shifting of seasonal weather phenomena and changes in precipitation patterns will be more in coming years.
Frequency of natural disasters like flood, cyclone, high tide etc. will increase; coastal areas and low lands will be submerged, desertification will escalate, agricultural production will drop, global biodiversity will be in danger, natural heritages would be destroyed, rivers will change their courses, fisheries and forest will be damaged, water security will be under stress and various health diseases will appear.
In this context, we have to bring to an end the use of chlorofluorocarbons, control the smoke of brick fields, industries and vehicles; discourage the use of wood and bio-fuels, step up tree plantation programmes all over the country, particularly in coastal areas; make effective contracts with the experts on environmental security and take necessary information on global climate, appeal to the global community to increase their technical and monitoring cooperation to combat the challenges of climate variation, set up effective and sustainable policies and strategies to face the implications of global warming and raise public awareness on ozone layer security and green house gases.
Incidences of global environmental insecurity are becoming increasingly diverse and more frequent due to the ozone layer depletion. Third world countries who are at the lowest rungs of the development ladder will be the greatest guiltless sufferers. Normally, environmental crisis is the consequence of affluence and poverty and the poorer countries have lesser ability to fight crises.
The 7.5 billion people inhabiting the earth may be living in different geographic and political units but they are the global community under a global environmental umbrella. Evert body including the common mass, environmentalists, engineers, chemists, biologists, researchers and political organizations will have to come forward and take necessary steps to bring back symmetry in nature and coalesce economy and environment to prevent ozone layer depletion and ensure environmental security.
The writer is an environment analyst and associate member of Bangladesh Economic Association.