Ncert Exercises & Solutions

Green plants use carbon dioxide for photosynthesis and return oxygen to the atmosphere, even then carbon dioxide is considered to be responsible for green house effect. Explain why?

Carbon dioxide is a natural constituent of atmosphere and is vital for all forms of plant life. It forms about 0.033% by volume of atmosphere. It helps to maintain the temperature of the earth required for living organisms.

A balance of CO₂ is maintained in air because CO₂ is produced from respiration, burning of fossil fuels and decomposition of lime stone but at the same time, it is consumed in photosynthesis by plants.

However, human activities have disturbed this balance and CO₂ level in atmosphere is in increasing order. This has happened due to deforestation, burning of more fossil fuel and industrialisation. It has been estimated that CO₂ concentration has risen about 25% in the past century.

During the past nearly 120 yaers, the average temperature of the planet has increased by somewhere between

0.4 ° C

0.8 ° C

. Current estimated are that doubling the CO₂ concentration will result in a temperature increase of between

1.0 ° C

and

3.5 ° C

. In green house effect, contribution of CO₂ is 50% and of other trace gases is also about 50%.

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