Question

4. The composition of the Earth’s atmosphere has changed in the past 200 years. What are/were the major changes in our atmospheric composition?

Answer 1

Ans) Major changes in our atmospheric composition in past 200 years are as follows :

1) Carbon dioxide gas concentration has increased about 35 % in last 200 years due to industrial revolution . The increase is primarily due to human use of fossil fuel and deforestation. Carbon dioxide is important greenhouse gas and this increase in its composition contribute in increase of greenhouse effect which result in global warming over the last 200 years

2) Methane , a strong greenhouse gas , concentration in atmosphere have increased by more than 150% in last 200 years.The primary source of increase in concentration of methane in atmosphere is rice cultivation , domestic animal grazing, coal mining and oil and gas extraction.

3) Concentration of another green house gas , Nitrous oxide is also increased in past 200 years due to land use conversion , burning of fossil fuels and soil fertilization.The average concentration of this gas is now increasing at a rate of 0.25% per year

4) Ozone - Ozone layer which exists majorly in earth stratosphere, absorb around 97% of harmful sun UV rays but since past 200 years this layer is badly affected due to human beings. The level of stratospheric ozone is decreasing due to increase in concentration of chlorofluorocarbon (CFC) in atmosphere because of human activities. In past 200 years around 3% of ozone is decreased due to which Montreal protocol is formed in 1987 which decreased emissions of ozone depleting substances by around 98% . Now, due to these efforts we see initial signs of recovery of ozone.