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?
Show answer
Answer: C. Statement I is correct: without the greenhouse effect of the atmosphere, Earth's average surface temperature would be about -18 C instead of about +15 C. Statement II is correct: heat absorbed and re-radiated by the atmosphere keeps the planet warm. Statement III is correct: gases like carbon dioxide and water vapour absorb outgoing long-wave (infrared) radiation. So all three are correct.
Watch for: The word 'everywhere' in Statement I may push students to reject it, but UPSC treats it as the standard greenhouse-effect fact.
Why the other options are wrong
- A. Wrong: Statement II is also correct.
- B. Wrong: Statement III is also correct.
- D. Wrong: Statement I is also correct.
Source to check: NCERT Class XI, Fundamentals of Physical Geography, chapter 'Solar Radiation, Heat Balance and Temperature'; NASA Earth Observatory pages on the greenhouse effect.
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.