| The heat caused by infrared radiation from the sun | | | | water vapor, nitrous oxide etc. are molecules formed |
| which escapes from the Earth's outer surface, is | | | | by two atoms which are loosely bound and are |
| absorbed by "greenhouse gases" which trap the heat | | | | thereby easily excited by solar radiation. The loose |
| forming a kind of blanket of warm air that surround | | | | atoms then pass on the heat to other gases by |
| the planet. This occurrence is called the "green house | | | | molecular interaction. Major components of the |
| effect". It is suggested that the temperature on | | | | atmosphere such as oxygen and nitrogen are formed |
| average would have been much lower compared to | | | | my tightly bound atoms which are not easily excited |
| what is now. Survival of the ecosystem would have | | | | and thus do not absorb heat. |
| been difficult in such extreme condition. | | | | EFFECTS ON GLOBAL WARMING |
| UNDERSTANDING THE GREENHOUSE EFFECT | | | | Though greenhouse effect is an essential |
| In the natural greenhouse effect, the type of the | | | | environmental phenomenon, the trouble begins when |
| type of topograph the sunlight falls plays a key role. | | | | human activities disturb or accelerate the natural |
| Different types of surfaces absorb or radiate heat | | | | process by creating more of the green house gases |
| differently. For example, white glaciers reflect | | | | necessary for the optimum warming of the earth |
| maximum sunlight resulting in minimum heating of the | | | | surface and thus raising the surface temperature |
| surface and the lower atmosphere. On the other | | | | above ideal one. |
| hand, sunlight is absorbed the maximum by dark | | | | Higher the concentration of the green house gases |
| desert soil causing more heating of the surface and | | | | more is the heat radiation towards the earth. The |
| the lower atmosphere. Clouds that cover the sky | | | | emission of green house gas such as carbon dioxide |
| reduce the amount of solar radiation penetrating onto | | | | is mainly due to burning of fossil fuels such as oil, gas, |
| the earth's surface and also reduce the amount of | | | | petrol, kerosene etc. |
| radiation emitted into space. | | | | Higher concentration of such man-made greenhouse |
| BASIC MECHANISM | | | | gas causes considerable warming of the earth and |
| About 50% of the solar radiation is absorbed by the | | | | the sea resulting in Global Warming. |
| earth's surface and the rest is emitted as infrared | | | | HUMAN CONTRIBUTIONo Level of carbon dioxide is |
| radiation by the surface of earth. Green house gases | | | | increased by burning of natural gas, coal, oil, petrol |
| absorb most of the infrared radiation and pass on to | | | | etc.o Some agricultural and land-use methods increase |
| the other atmospheric gases by molecular interaction. | | | | the level of methane and nitrous oxide in |
| The greenhouse gases too radiate some heat. Heat | | | | atmosphere.o Industrial wastes and gases contribute |
| is radiated both upwards and downwards with some | | | | substantially to the green house effect and thus |
| escaping into the space and some getting back to | | | | adding to global warming.o Deforestation is one of |
| the earth surface. The earth surface and the lower | | | | the major causes of global warming today.o |
| atmosphere is thus aiding to the survival of life on | | | | Population explosion is another prime factor |
| earth. | | | | contributing towards global warming. |
| Greenhouse gases such as carbon dioxide, methane, | | | | |