UPSC Prelims 2014 · Question 93 of 100

UPSC Prelims 2014 question on Global Warming Two Degree Limit

The scientific view is that the increase in global temperature should not exceed 2°C above pre-industrial level. If the global temperature increases beyond 3°C above the pre-industrial level, what can be its possible impact/impacts on the world?

1. Terrestrial biosphere tends toward a net carbon source.
2. Widespread coral mortality will occur.
3. All the global wetlands will permanently disappear.
4. Cultivation of cereals will not be possible anywhere in the world.

Select the correct answer using the code given below.

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

Answer: B. 1 and 2 only

Verdict

The answer is 1 and 2 only. Beyond three degrees of warming the terrestrial biosphere may turn into a net carbon source and widespread coral mortality is expected, but the wetland and cereal statements are far too extreme.

Analysis

Statement 1 is CORRECT. Warming increases respiration and disturbance losses and can push forests and soils from absorbing more carbon than they release to releasing more than they absorb. Statement 2 is CORRECT. Corals bleach and die at sustained elevated sea temperatures, and widespread mortality is a standard projection at this level of warming. Statement 3 is INCORRECT because of the word all and the word permanently. Statement 4 is INCORRECT because it claims cereal cultivation would be impossible anywhere in the world, whereas higher latitudes may even gain.

Source

Assessment literature on the effects of global warming.

How to crack it

This is applied reasoning, not recall. Scientific projections are stated in terms of risk, degree and region, so any statement written in absolutes, all, permanently, anywhere, nowhere, is almost certainly a distractor. Grade each statement for the strength of its claim before checking the science, and the two extreme statements fall immediately, leaving the two moderate ones. The same calibration test works across the entire climate change question set.

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