Social Environment: Issues And Challenges | Social Problems
The characteristic pattern of weather elements in an area over a period is called climate. The weather elements include temperature, rainfall, humidity, solar insolation, wind, etc. large-scale deforestation has badly affected the weather, facing almost each year of break than the normal year. World climate is not fixed. During the first half of the 20th century, the atmospheric circulation in the northern hemisphere was predominantly zonal, west to east, which resulted in a relatively stable weather pattern. Since then, the circulation has developed a more pronounced wave-like pattern with greater north-south and south-north flows resulting in more perturbations in weather. Overall, the main trend seems to be toward more frequent extreme weather conditions such as floods, droughts, cold & warm spells in widely separated areas. Monsoon rains in south Sahara became favorable from 1920-1960’s but this trend reversed in recent times. On the contrary, in Rajasthan desert, rainfall has increased very much in the last ten years, resulting into floods in certain areas where rainfall was scanty.
The increase in concentration of greenhouse gases, for example- CO2, CH4 (methane), NO (Nitrous oxide), CFCs and Hydroflouro-carbons retain more and more the infrared radiations, resulting in enhanced greenhouse effect. The consequent increase in the global warming. It is estimated that CO2 contributes about 60% of the total global warming.
Some important facts of global warming are:
Effects on weather and climate:
Rise in temperature would cause widespread changes in precipitation patterns. Winter precipitation may decrease at lower latitudes. Besides, the frequency of extreme events (e.g. droughts, flood, etc.) is expected to increase substantially. The climate change will increase threats to human health due to change in ranges of disease vectors, water borne pathogens, etc.
Sea Level Change:
Sea level rise is projected to have negative impact on human settlements, tourism, freshwater, supplies, fisheries, exposed infrastructure, agriculture and drylands, wetlands. A rise of even half a meter sea level would affect human population, 1/3rd of which lives within 60km of coastline.
Effects on range of species distribution:
The global warming is likely to shift the temperature ranges and therefore, would affect attitudinal and longitudinal distribution pattern of organism. Many species will not tolerate the rise in temperature and will disappear.
Global warming will decrease food production due to increased rate of respiration, eruption of plant diseases, pests, etc. in Southeast Asia, the rice yield will reduce by 5% for each 1o C rise in temperature.
Reducing the green house emission by limiting the use of fossil fuels, increasing the vegetation cover, minimizing the use of nitrogen fertilizers, developing substitutes for CFCs are some of the important methods to check global warming.
Ozone layer Depletion
UV radiation causes photo dissociation of ozone into O2 and O in the stratosphere. But O2 and O quickly recombine to form O3. This ozone dynamics dissipates the energy of UV as heat. An equilibrium is established between generation and distraction of O3, leading to a steady state concentration of ozone layer in the stratosphere between 20 to 26 km above the sea level. This ozone layer acts as ozone shield protecting the earth biota from harmful effects of strong UV radiation.
CFCs, CH4, and N2O escape into the stratosphere and cause destruction of O3 there. This is known as Ozone Layer Depletion. Most damaging is the effect of CFCs, which produce “active chlorine” in the presence of UV radiation. These radicals catalytically destroy ozone, converting it into oxygen.
Effect of Ozone Depletion
The thinning of the ozone layer results in an increase in the UV-B radiation reaching the earth surface. It results in the following processes:
- The incidence of skin cancer and cataract increases.
- Diminishes the immune system
- Elevated levels of UV-B radiation affect photosynthesis in most phytoplanktons as it penetrates through the clear open ocean water. So, the whole food chain of organisms that depend of phytoplanktons is affected.
In a broad sense, acid rain refers to several ways in which acids from the atmosphere are deposited on the earth. Acid deposition includes wet and dry deposition.
Wet deposition refers to acidic water received through rain, fog and snow. Dry deposition related to the winds blown acidic gases and particles in the atmosphere, which settle down on the ground. Nitrogen oxides, SO2 are highly reactive in air. They rapidly oxidize into acids (Sulphuric or nitric acid), which quickly dissolve in water and washed to the ground as acid rain.
Nuclear Accidents and Holocausts
Atom bombs was dropped on Hiroshima (6th August, 1945, 8:15am, atomic bomb named “Little Boy”). When the atom bomb was dropped over Hiroshima, the sun went out, a white blinding light obscured the sun. The sky was covered with a sudden mist formed of very small particles of brick and stone, of vegetation and human tissues. There was no sound or thud. The after effects of the atom bomb were even more horrible. 1,40,000 lives were lost, 80% of buildings were wiped out. All the survivors suffered from one disease or other. Many became victims of radiations. Many other became incapable of reproduction. Falling of hair, high fever and low blood count were other harmful effects of the atom bomb. Pregnant women aborted and long term genetic problems were developed.
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