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RAS question

Which of the following is a Greenhouse Gas? 1. Water vapor 2. Carbon dioxide 3. Nitrogen 4. Ozone

Correct answer: (B) 1, 2 and 4.

Water vapour, carbon dioxide and ozone are greenhouse gases, while nitrogen is not.

  1. (A)

    1, 2, 3 and 4

  2. (B)

    1, 2 and 4

  3. (C)

    1 and 2 only

  4. (D)

    2 and 3 only

Explanation

The answer is 1, 2 and 4: water vapour, carbon dioxide and ozone. The IPCC describes greenhouse gases as atmospheric gases that absorb and emit radiation at specific wavelengths in radiation emitted by Earth's surface, the atmosphere and clouds, causing the greenhouse effect. In the same FAQ, it lists water vapour, carbon dioxide and ozone among the primary greenhouse gases in Earth's atmosphere. Nitrogen is different: although it makes up 78% of the atmosphere, nitrogen is not a greenhouse gas because it does not absorb infrared radiation significantly. That is why the set including nitrogen is rejected, and the set containing water vapour, carbon dioxide and ozone is accepted.

Why the other options are wrong

  • (A) Option A wrongly includes nitrogen, which is not a greenhouse gas because it does not absorb infrared radiation significantly.
  • (C) Option C leaves out ozone, although the IPCC FAQ lists ozone among the primary greenhouse gases in Earth's atmosphere.
  • (D) Option D wrongly includes nitrogen and also omits water vapour, the most abundant greenhouse gas.

Concept

This tests the Environment and Ecology concept of greenhouse gases and the physical basis of the greenhouse effect. It recurs in RAS because climate change questions often require separating common atmospheric gases from gases that actually absorb and emit infrared radiation.

Source

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