UPSC Prelims 2011 · Question 91 of 100

UPSC Prelims 2011 question on Carbon Dioxide Ocean Sink

Human activities in the recent past have caused the increased concentration of carbon dioxide in the atmosphere, but a lot of it does not remain in the lower atmosphere because of

1. Its escape into the outer stratosphere.

2. The photosynthesis by phytoplankton in the oceans.

3. The trapping of air in the polar ice caps.

Which of the statements given above is/are correct?

  1. 1 and 2
  2. 2 only
  3. 2 and 3
  4. 3 only
Show answer

Answer: B. 2 only

Verdict

Correct Answer: 2 only

Only statement 2 is correct because oceanic phytoplankton reduce atmospheric carbon dioxide through photosynthesis.

Analysis

Human activities have increased carbon dioxide in the atmosphere, but its concentration is partly reduced by natural carbon sinks, especially oceans and photosynthetic organisms.

Statement by statement

1. Escape into the outer stratosphere — Incorrect

Carbon dioxide does not significantly escape into the outer stratosphere or space.

It remains mainly in the lower atmosphere and contributes to the greenhouse effect.

2. Photosynthesis by phytoplankton in the oceans — Correct

Phytoplankton absorb carbon dioxide during photosynthesis.

This helps remove carbon dioxide from the atmosphere because oceans act as major carbon sinks.

3. Trapping of air in polar ice caps — Incorrect

Ice cores contain trapped air from the past, which helps scientists study ancient climate.

But this is not a major process for reducing present-day atmospheric carbon dioxide.

Extra UPSC info

* Oceans are among the largest active carbon sinks.

* Phytoplankton are microscopic marine organisms that perform photosynthesis.

* Forests and soils are important terrestrial carbon sinks.

* Carbon dioxide absorption by oceans can lead to ocean acidification.

* The biological pump transfers carbon from surface waters to deeper ocean layers.

* Do not confuse climate records in ice cores with active carbon removal.

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