Authentic Classroom Explanation by IAS Monk

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📌 Question

Consider the following statements:

Statement I:
Without the atmosphere, temperature would be well below freezing point everywhere on the Earth’s surface.

Statement II:
Heat absorbed and trapped by the atmosphere maintains our planet’s average temperature.

Statement III:
Atmosphere’s gases, like carbon dioxide, are particularly good at absorbing and trapping radiation.

Which of the statements given above are correct?
(a) I and III only
(b) I and II only
(c) I, II and III
(d) II and III only

✅ Correct Answer: (c)

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🎯 Theme of the Question

Climatology | Atmosphere | Greenhouse Effect | Earth’s Energy Balance | Physical Geography

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🧠 Classroom Explanation

This question directly tests your conceptual clarity on the natural greenhouse effect, a high-frequency UPSC theme that bridges Geography + Environment + Climate Change.

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🔹 Statement I Analysis

Without the atmosphere, temperature would be well below freezing everywhere on Earth.

✔️ Correct.

• Without atmosphere:
  • No greenhouse effect
  • Heat radiated from Earth would escape directly into space
• Earth’s average temperature would drop to around –18°C
• Comparable example: Moon, which has:
  • No atmosphere
  • Extreme temperature variations

👉 Atmosphere acts as a thermal blanket.

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🔹 Statement II Analysis

Heat absorbed and trapped by the atmosphere maintains Earth’s average temperature.

✔️ Correct.

• Incoming solar radiation:
  • Short-wave radiation enters easily
• Outgoing terrestrial radiation:
  • Long-wave (infrared) radiation is partially trapped
• This process keeps Earth’s average temperature at around:
  • 15°C (59°F)

👉 This is the natural greenhouse effect, essential for life.

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🔹 Statement III Analysis

Atmospheric gases like CO₂ are particularly good at absorbing and trapping radiation.

✔️ Correct.

• Greenhouse gases include:
  • Carbon dioxide (CO₂)
  • Methane (CH₄)
  • Water vapour (H₂O)
  • Nitrous oxide (N₂O)
• These gases:
  • Absorb outgoing infrared radiation
  • Re-radiate it back toward Earth

👉 Without these gases, Earth would be a frozen planet.

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✅ Final Verdict

All three statements are scientifically correct and together explain how Earth maintains a life-supporting temperature.

👉 Correct Answer: (c) I, II and III

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🧠 Concept Lock Table

Concept	Role
Atmosphere	Heat regulator
Greenhouse gases	Trap infrared radiation
Without atmosphere	Earth ≈ –18°C
With atmosphere	Earth ≈ +15°C

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🧠 Memory Hook

“No air, no warmth — Earth turns Moon-like.”

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🔍 Curiosity Corner

Why is Venus hotter than Mercury, even though Mercury is closer to the Sun?

Because:

• Venus has a dense CO₂-rich atmosphere
• Runaway greenhouse effect traps enormous heat

👉 Atmosphere matters more than distance.

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📘 Enrichment Note

UPSC Trick Zone:

• Natural greenhouse effect = essential
• Enhanced greenhouse effect = problematic
• UPSC often tests whether aspirants:
  • Confuse greenhouse effect with ozone layer
  • Treat greenhouse effect as always harmful

⚠️ Remember: Life exists because of the greenhouse effect.

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🎯 Prelims Strategy Insight

When a question links:

• Atmosphere
• Radiation
• Temperature

👉 Expect all statements to be correct, unless a subtle distortion is inserted.

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🧩 One-Line Ready Recall

Atmosphere traps heat → Greenhouse gases absorb IR → Earth stays habitable

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🧭 IAS Monk Whisper
The sky is not empty — it is Earth’s quiet guardian.