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Greenhouse Gases and the Ozone Layer: asked and not asked.

UPSC has asked 13 of these 20. 8 came more than once. 7 have not come yet. Lock the repeated ones first, then read the rest.

First, the concept

Sunlight warms the Earth; the Earth gives the heat back as infrared rays. Greenhouse gases absorb part of it and keep the planet warm. More of these gases means more warming.

The ozone layer is a different story: it sits in the stratosphere (about 15–35 km up) and blocks harmful ultraviolet (UV-B) rays. CFCs break it down.

Ozone near the ground is a pollutant and a greenhouse gas. Ozone high up is a shield. UPPCS likes this contrast.

🔁 Asked again and again (8)

Tap a year to open that solved question.

The gases

Warming ideas

  • Carbon sink · Oceans are the largest; forests and soil also store carbon 8 times:202520232020201720172012
  • Albedo · How much sunlight a surface reflects; snow high, forest low 2 times:20082002

Ozone layer

✅ Asked once (5)

The gases

  • Sulphur hexafluoride · Electrical equipment; the highest global warming potential 2010

Warming ideas

  • Blue carbon · Carbon stored by mangroves, seagrass and salt marshes 2021
  • Ocean acidification · Sea water takes in CO₂ and turns more acidic; harms corals and shells 2012

Ozone layer

  • Ozone hole · Over Antarctica, in spring (September–October) 2011
  • World Ozone Day · 16 September (Montreal Protocol was signed on this day in 1987) 2001

❌ Not asked by UPSC yet (7)

Items marked 'asked in UPPCS' have already come in the UP state exam, so examiners do use them.

The gases

  • Not greenhouse gases · Nitrogen, oxygen and argon asked in UPPCS

Warming ideas

  • Global Warming Potential · Heat trapped by a gas compared with CO₂ over 100 years asked in UPPCS
  • Coral bleaching · Warm water makes corals throw out their algae and turn white asked in UPPCS
  • Permafrost thaw · Frozen ground melting and releasing methane

Ozone layer

  • Ozone-depleting substances · CFCs, halons, carbon tetrachloride, methyl bromide asked in UPPCS
  • Dobson unit · Unit for measuring the ozone layer
  • Polar stratospheric clouds · Very cold clouds on which chlorine attacks ozone

⚠️ The ozone hole is over Antarctica, not the Arctic. CFCs harm the ozone layer; HFCs do not, but they warm the planet. Argon is not a greenhouse gas.

'Asked' is checked against the solved UPSC questions on this site. 'Not asked yet' does not mean it will surely come.

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