Q. Consider the following statements :
1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
2. Low clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause warming effect.
Which of the statements given above is/are correct ?
a) 1 only
b) 2 only
c) Both 1 and 2
d) Neither 1 nor 2
Correct Answer: d) Neither 1 nor 2
Question from UPSC Prelims 2022 GS Paper
Explanation :
High and Low Clouds
The two statements provided address the effects of high and low clouds on Earth’s climate, specifically in terms of their interactions with solar radiation and infrared radiation. Let’s examine each statement:
High Clouds and Solar Radiation
The first statement suggests that high clouds primarily reflect solar radiation and cool the surface of the Earth. However, this is not entirely accurate. High clouds, such as cirrus clouds, are thin and often composed of ice crystals. They do reflect some incoming solar radiation, but they also allow sunlight to pass through and reach the Earth’s surface. Furthermore, high clouds are effective at trapping outgoing infrared radiation emitted by the Earth, leading to a warming effect known as the greenhouse effect. Consequently, the net effect of high clouds on Earth’s climate can be warming, rather than cooling.
Low Clouds and Infrared Radiation
The second statement claims that low clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause a warming effect. This statement is also not entirely correct. Low clouds, such as stratus clouds, are typically thicker and have a high albedo, meaning they are good at reflecting incoming solar radiation back into space, which tends to cool the Earth’s surface. While they do absorb some infrared radiation, they are more effective at reflecting it. The overall effect of low clouds is often a cooling one, as they reflect more sunlight than the amount of infrared radiation they trap.
Given the explanations above, the correct answer is “Neither 1 nor 2” because both statements contain inaccuracies regarding the effects of high and low clouds on Earth’s climate. High clouds can have a net warming effect due to their greenhouse properties, and low clouds generally have a net cooling effect because of their ability to reflect sunlight.
