The causes of global warming & Green-house Effect

Air contains 0.03 percent of carbon dioxide. However the atmosphere content of carbon dioxide is increasing day by day due to indiscriminate use of fossil fuels. This releases carbon dioxide gas in the atmosphere. The solar energy which reaches the earth a part of it is radiated, however carbon dioxide acts as a sheet and prevents, escape radiated heat energy which now remains in the atmosphere and it gets heated. This way temperature of the earth is increasing slowly day by day. This is to referred to as ‘Global Warming’. There are some causes for increasing global warming which are given below-

5 important causes of global warming:

1.   The temperature of the earth increase due to increases use of, composition of fossil fuel which releases carbon dioxide in the atmosphere.

2.   The amount of carbon dioxide is increasing due to the use of wood as fuel.

3.   Methane’s produced in paddy field and Murphy land by rotting and decomposition of plants by bacteria and from cow dung rotten organic derbies etc. increases temperature of the earth.

4.   CFC is used in cold storage, refrigerator, motor vehicles etc. This in turn mixes in the air. It increases the temperature at high rate.

5.   The amount of nitrous oxides increases due to deforestation and use of nitrogenous fertilizer. As a result of temperature of the air has been increasing.

Means of combing be global warming:

At a global conference in 1992, 153 nations discussed on climate changes and concluded to work towards reducing the emission of green house gases mainly carbon dioxide. The measures to be taken are as follows:-

1.   Consumption of fossil fuels to be reduced the production of carbon dioxide will decreases with the reduction of use of fossil fuels.

2.   The non-conventional sources of energy such as solar energy, wing prowess etc. should be used in place of fossil fuels.

3.   Natural gas can be used in place of coal because its carbon content is half than that of coal and contains no sulphur .

4.   Fuel efficient vehicle should be designed.

5.   The production and uses of chloro-fluro carbon should be lowered as far as possible.

6.   A forestation is another step to decrease the concentration of carbon dioxide. Because plants use carbon dioxide for manufacture of food in the process of photosynthesis and release oxygen.

7.   People should be made aware about bad effects of global warming.

Green-house effect

Carbon dioxide gas present in atmosphere performs an important function in the atmosphere and produces the green-house effect, leading to the heating up of earth and its atmosphere. Let us discuss it in detail. There is a protective layer of ozone gas, high up in the atmosphere and then a blanket of carbon dioxide gas in the lower atmosphere. Now, when sun-light consisting of ultra-violet rays, visible light and infra-red rays, falls on the top of the atmosphere, then first of all the harmful ultra-violet radiation is absorbed by the ozone layer. The visible light and infra-red rays then pass through the carbon dioxide layer and fall on the surface of earth.

The infra-red rays which come down from the sun are of short wavelength and pass through the carbon dioxide layer easily. Since the infra-red radiation has heating effect, so it heats the earth and the various objects on the earth. Now, since the earth and its objects become hot, so they also start emitting heat rays or infra-red rays. But since the earth's surface and the objects on it are less hot so the infra-red rays emitted by them are of long wavelength. In other words, the infra-red rays which fall on the earth from sun are of short wavelength but the infra-red rays reflected from the earth and its objects are of long wave­length.

Now, this long wavelength infra-red radiation reflected from the earth and its objects cannot escape out from the carbon dioxide layer in the atmosphere. Since the carbon dioxide molecules have the ability to absorb the long wavelength infra-red radiation reflected from the earth, so a blanket of carbon dioxide gas in the atmosphere traps all the infra-red rays or heat rays in the atmosphere. And these trapped infra-red rays or heat rays heat the earth's atmosphere. The heating up of earth's atmosphere due to the trapping of infra-red rays (reflected from the earth's surface) by the carbon dioxide layer in the atmosphere is called green-house effect.

The green-house effect in the atmosphere occurs due to the presence of a blanket of carbon dioxide gas in the atmosphere. This blanket of carbon dioxide gas in the atmosphere allows the sunlight to come in freely but does not allow the infra-red radiation reflected by the earth's surface to go out. It is just because the sun-light can come in freely but the infra-red rays cannot go out freely that the temperature of earth's atmosphere is raised. It should be noted that the rise in temperature produced by green-house effect in earth's atmosphere depends on the amount (proportion) of carbon dioxide gas in the atmosphere.

In other words, the proportion of carbon dioxide in atmosphere affects the temperature of atmosphere. So, if the proportion of carbon dioxide gas in the atmosphere increases, then the temperature of earth's atmosphere will also rise further. The name 'green-house effect' comes from the fact that this effect is used in horticulture for the upbringing of green plants in small houses made of glass walls and glass roof. The glass walls and roof of a green-house allow the sun-light (including short wavelength infra-red rays) to come in freely but it does not allow the long wavelength infra-red radiations reflected by the soil, plants and other contents of green-house to go out. These trapped infra-red rays show their heating effect due to which the temperature is raised inside the green-house.

Thus, even without an external supply of heat, the temperature inside a green-house is found to be higher than it is outside. Thus, green-house acts as a heat trap. Due to the presence of carbon dioxide, our atmosphere acts like the glass roof of an ordinary horticultural green-house.