Question

Greenhouse effect means
A) Increase in the temperature of the earth due to high concentrations of $NO_2$
B) Increase in the temperature of the earth due to high concentrations of $SO_2$
C) Increase in the temperature of the earth due to high concentrations of $CO$
D) Increase in the temperature of the earth due to high concentrations of $CO_2$

Answer 1

The greenhouse effect is an absolutely natural phenomenon. It is caused by the presence of certain gases in the earth’s atmosphere that prevents some of the heat brought by the sun’s rays from being radiated and lost back to space.

Complete answer:
Though this is a natural effect that helps regulate the surface temperature of the earth thereby making our planet liveable, human activities over the last century or so have affected this balance. Increased industrialisation, air pollution, drastic decreases in forest cover, and intensive livestock farming have increased the concentration of carbon dioxide, methane, ozone, and water vapour.

Nitrogen dioxide is not one of the greenhouse gases, option A is incorrect.

While levels of sulphur dioxide have risen due to industrial activity, it is not a greenhouse gas. Option B is incorrect.

$CO$ is produced due to burning fuels and from car exhausts. However, while extremely toxic to us, it is not a greenhouse gas. Option C is incorrect.

$CO_2$ is one of the gases involved in deflecting heat back towards the surface of the earth and causing the temperatures to increase. As forests are lost and ocean pollution increases, there is much less photosynthetic activity and lower and lower amounts of carbon dioxide are fixed.

Hence the correct answer is option D.

Note: While greenhouses are regulated environments for the growing of crops, they have disadvantages like pest problems as the natural control for pests is not available in this artificial situation.