The plants and animals balance carbon dioxide level of the atmosphere which in twin acts as global thermostat.
It means these elements control the temperature balance within optimum limits.
The water bodies play important role in regulating global climate.
Green House Effects and Global Warming
Global warming refers to a gradual rise of atmospheric temperature and consequent changes in the radiation balance mainly due to human action leading to climatic change at different levels – local, regional and global.
This is due to green house effect.
Green House gases are carbon dioxide (CO2), methane (CH4) nitrous oxides (NOx) and chlorofluorocarbon (CFC) and hence known as green house gases.
Out of these four gases, carbon dioxide contributes about 55%, chlorofluorocarbon contributes about 24%, methane (about 15%) and nitrous oxide (about 6%) towards heating of the atmosphere.
The sources of these gases
Carbon dioxides– Burning of fossil fuels and fire woods, large fleet of automobiles and number of factories emit
Methane– Growing paddies, livestock, waste dumps and coal mining
Chlorofluorocarbons– The use of aerosols as coolants in refrigerators and air conditioning devices
Nitrous oxide– Chemical industries, Deforestation and certain agricultural practices.
Consequences of green house effect
It is estimated that if the present rate of increase in CO2 level continues, it will result in rise of atmospheric temperature by 20C to 30C by end of 21st century.
This will result in receding many glaciers; melting of icecaps in the Polar Regions and disappearance of deposits of ice on the other parts of world in large scale.
A rise in sea-level of only 50-100 cm caused by global warming would flood low lying areas of the world such as Bangladesh, West Bengal as well as densely populated coastal cities from Shanghai to San-Francisco.
Because of increased concentration of CO2 and due to much warmer tropical oceans, there may occur more cyclones and hurricanes.
Early snow melt in mountains will cause more floods during monsoon.
A slight increase in global temperature can adversely affect the world food production.
Thus the wheat production zones in the northern latitudes will be shifted to north of temperate latitudes.
The biological productivity of the ocean would also decrease due to warming of the surface layer, which in turn reduces the transport of nutrients from deeper layers to the surface by vertical circulation.
Working of a Green House —
In cold countries, a green house is meant for plants, where total heat, especially during winter season, is not sufficient to support plant growth.
The transparent walls and roof of the green house are such that these allow the visible sunlight to enter but prevent the long-wave radiations to go out.
Thus, the sunlight is absorbed by the soil and structure of the green house.
It is then re-emitted as heat which cannot pass through the glass.
The amount of energy in the green house thus increases until its temperature is high enough for the slight leakage of heat through the glass to take away as much energy as gets in as sunlight.
Subsequently walls and roof re-emit absorbed radiation into the house.
Thus, during the day time, infra-red radiations pass into the green house and warm the atmosphere and the ground on which the green house stands.
Coating of glass with a non-heat radiation film transparent to sunlight further maximizes heating effect of the radiation.
Control and Remedial Measures of Green House Effect —
The following measures may be adopted to reduce the ever increasing green house effect.
CO2 concentration can be reduced by drastic cut in the consumption of fossil fuels in the highly developed and industrialized countries like USA and Japan and developing country like China and India.
Methane may be a substitute of petroleum.
Development of hydro-electric and thermal power are better alternatives.
There should be a restriction on the emission of dangerous CO2, CFCs, and as NO2 from the factories and automobiles.
Limiting the driving days in mega cities can be another option. Cities like Singapore and Mexico are following the practice.
Biogas plants should be used which is another source of conventional energy for domestic use.
Enhancing afforestation will certainly reduce the CO2 level thereby decreasing the green house effect.