Normally, the temperature decreases with the increase in height from the Earth’s surface, because:

Answer: (c) 1 and 3 only

The atmosphere is warmed mainly from below, by long-wave heat radiated from the Earth's surface. Air higher up is thinner, so it holds and absorbs less of that heat and is cooler. The upper atmosphere has less moisture, not more.

• ✓ 1. Incoming solar radiation passes through the air without heating it much. The ground absorbs it and radiates long-wave heat upwards. So the air near the surface is warmest, and temperature falls as you go up.
• ✗ 2. Water vapour is concentrated near the surface and decreases with altitude. The upper atmosphere is therefore drier, and moisture cannot explain the fall in temperature.
• ✓ 3. Gravity packs air close to the surface, so the lower air is denser. Higher up the air is thin and has fewer molecules to absorb the Earth's outgoing heat, so it stays cooler.

Remember · The atmosphere is heated from below by terrestrial (long-wave) radiation. In the troposphere temperature falls about 6.5 °C per km. Water vapour and air density both decrease with height.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 8 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 7 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 9 (practise this chapter)

Question: UPSC Civil Services (Preliminary) 2012, General Studies Paper I. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). · Report an error