Write a short note on global warming. Name some gases which cause greenhouse effect. What are the harmful consequences of this effect?
The greenhouse effect received its name because the earth's atmosphere acts much like the glass or plastic roof and walls of a
greenhouse. Sunlight enters a greenhouse through the transparent roof and heats the plants but the heat emitted by the plants in the form of infrared radiation cannot pass through roof and walls. As a result, the temperature inside the house increases. An effect similar to the greenhouse
is responsible for keeping the earth's surface warmer. The atmosphere around the earth acts like a glass of the greenhouse chamber. This is known as
greenhouse effect.
Most of the heat radiated by the earth is absorbed by gases in the atmosphere and re-radiated back to the earth's surface. This increases the global temperature. This is known as global warming.
The gases present
in the atmosphere which are responsible for greenhouse effect and global warming are carbon dioxide, oxides
of nitrogen, methane, ozone, chlorofluorocarbons, etc.
Harmful consequences of the greenhouse effect are:
i) Rise in sea level - Higher sea level is caused when glaciers at the poles melt because of global warming. This would increase the frequency and severity of floods, damage coastal areas, i.e., low lying areas would submerge.
ii) Changing patterns of rainfall - Patterns of rainfall would change worldwide causing large shifts in agriculturally productive areas.
iii) Evaporation of water from aquatic systems: Global warming will cause more water to evaporate from aquatic systems and increase the concentration of water vapour in the atmosphere. The extra water vapour will amplify warming because water vapour itself is a greenhouse gas.