Authentic Classroom Explanation by IAS Monk

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📍 The Question

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

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✅ Correct Answer: (d) Neither 1 nor 2

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🎯 Theme of the Question

Physical Geography | Climatology | Clouds | Earth’s Radiation Budget

This question tests conceptual clarity on cloud type vs radiation effect, a subtle but highly testable NCERT concept.

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🧠 Classroom Explanation

Understanding this question requires knowing how different cloud types interact with solar (shortwave) and terrestrial (longwave) radiation.

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🔹 Statement 1: High clouds primarily reflect solar radiation and cool the Earth ❌

This statement is incorrect.

• High clouds (cirrus-type):
  • Are thin and wispy
  • Allow most incoming solar radiation to pass through
  • But trap outgoing longwave (infrared) radiation
• Net effect:
  • Warming of the Earth’s surface

✔️ High clouds act more like a blanket, not a mirror.

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🔹 Statement 2: Low clouds absorb infrared radiation and cause warming ❌

This statement is also incorrect.

• Low clouds (stratus, cumulus):
  • Are thick and dense
  • Strongly reflect incoming solar radiation
• Net effect:
  • Cooling of the Earth’s surface

✔️ Low clouds have a cooling (albedo) effect, not warming.

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🔄 Correct Conceptual Mapping (Very Important)

Cloud Type	Dominant Effect	Net Impact
Low clouds	Reflect solar radiation	Cooling ❄️
High clouds	Trap infrared radiation	Warming 🔥

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📊 Final Assessment

Statement	Status
1. High clouds cool Earth	❌
2. Low clouds cause warming	❌

👉 Answer: (d) Neither 1 nor 2

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🧩 Memory Hook

“Low clouds reflect, high clouds trap.”

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🧠 Prelims Strategy Insight

UPSC often:

• Reverses cloud effects deliberately
• Tests whether aspirants confuse:
  • Reflection vs absorption
  • Shortwave vs longwave radiation

Always remember:

• Cooling = reflection of solar radiation
• Warming = trapping of terrestrial radiation

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🧭 IAS Monk Whisper

Not all clouds cool,
and not all warmth comes from the Sun.