Consider the following statements:
- I.Without the atmosphere, temperature would be well below freezing point everywhere on the Earth's surface.
- II.Heat absorbed and trapped by the atmosphere maintains our planet's average temperature.
- III.Atmosphere's gases, like carbon dioxide, are particularly good at absorbing and trapping radiation.
Which of the statements given above are correct?
Answer & explanation
Answer: (c) I, II and III
All three describe the natural greenhouse effect. The Earth's surface re-radiates sunlight as infrared heat; gases such as carbon dioxide, methane and water vapour absorb much of it, which keeps the global average near 15°C. Remove that blanket and the surface would be about 33°C colder, below freezing.
- ✓ I Without the atmosphere's greenhouse effect the average surface temperature would fall by roughly 33°C, from about 15°C to around −18°C, too cold for life.
- ✓ II The heat that the atmosphere absorbs and traps is what holds the planet's average temperature at a life-supporting level.
- ✓ III Carbon dioxide, methane and water vapour absorb the infrared heat re-radiated by the surface and stop it escaping to space.
Remember · Natural greenhouse effect: CO2, CH4, water vapour trap outgoing infrared; keeps Earth ≈ 15°C instead of ≈ −18°C (a 33°C difference).
📘 Read it in NCERT: Class 9 Exploration, Ch 13 (practise this chapter)
Sources
- NCERT Class 9 · Exploration, Chapter 13 “Greenhouse gases like CO2, CH4 and water vapour absorb this re-radiated heat, preventing it from escaping into space. Without the atmosphere, the Earth would be too cold for life to survive.”
- NASA Science: What is the greenhouse effect? ↗ “If carbon dioxide were removed, the terrestrial greenhouse effect would collapse, and Earth's surface temperature would drop significantly, by approximately 33°C (59°F). … Part of what makes Earth so amenable is its natural greenhouse effect, which maintains an average temperature of 15 ° C (59 ° F) .”
Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·