UPSC Prelims 2022 Q81: Geography – Atmosphere & Climatology
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
Answer: (d) Neither 1 nor 2
Explanation
How clouds affect Earth's temperature
Both statements reverse the real roles of high and low clouds.
| Cloud type | Example | Main effect | Net result |
|---|---|---|---|
| High clouds | Cirrus | Thin, so sunlight passes through; they trap outgoing infrared | Warming |
| Low clouds | Stratus, stratocumulus | Thick and bright, they reflect sunlight back to space | Cooling |
Checking the statements:
| Statement | Verdict | Why |
|---|---|---|
| 1. High clouds mainly reflect sunlight and cool the surface | Incorrect | High clouds mainly absorb and re-emit infrared, causing warming |
| 2. Low clouds absorb infrared and cause warming | Incorrect | Low clouds mainly reflect solar radiation, causing cooling |
Answer: (d) Neither 1 nor 2.
Why each option is right or wrong
- (a) Incorrect. High clouds like cirrus mainly trap heat and warm the surface.
- (b) Incorrect. Low clouds mainly reflect sunlight and cool the surface.
- (c) Incorrect. Both statements swap the roles of high and low clouds.
- (d) CORRECT. High clouds warm (trap infrared) and low clouds cool (reflect sunlight), so both statements are wrong.
Key point
High (cirrus) clouds trap outgoing infrared → warming. Low (stratus) clouds reflect sunlight → cooling.
Remember
High clouds warm, low clouds cool.
Common mistakes
- Assuming all clouds cool the Earth because they block the Sun.
- Not noticing that the two statements have swapped the roles of high and low clouds.
- Forgetting that thin cirrus clouds let sunlight in but block outgoing heat.
Exam tip
High = heat trap; Low = light reflector. Remember 'H for heat'.
Sources
- NASA Earth Observatory — Clouds and Radiation
- NCERT Class XI — Fundamentals of Physical Geography, Ch 9 (Solar Radiation, Heat Balance and Temperature)