UPSC Prelims 2010 · General Studies
Question 149: Environment and Ecology
Consider the following which can be found in the ambient atmosphere :
- 1.Soot
- 2.Sulphur hexafluoride
- 3.Water vapour
Which of the above contribute to the warming up of the atmosphere ?
AnswerThe answer is (d).
All three warm the atmosphere. Water vapour is the most abundant greenhouse gas. Sulphur hexafluoride (SF6) is a very potent, long-lived greenhouse gas used in electrical equipment, with a global warming potential over 20,000 times that of carbon dioxide over a century, and it is covered by the Kyoto Protocol. Soot (black carbon) absorbs sunlight and warms the air, and also darkens snow, speeding its melting. Remember: black carbon is a short-lived climate pollutant.
- 1. Soot absorbs sunlight and warms the air.
- 2. SF6 is an extremely potent greenhouse gas.
- 3. Water vapour is the most abundant greenhouse gas.
How you could have got this
- If you were sure statement 1 is correct, (b) and (c) go: each of them leaves 1 out.
What you needed to know: Soot absorbs sunlight and warms the air.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Water vapour is the most abundant greenhouse gas.
Only (d) is left. You didn’t need statement 2.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Leaves out water vapour, a major greenhouse gas.
- (b) Leaves out soot and SF6, which also warm the atmosphere.
- (c) Leaves out soot, which absorbs sunlight.
- (d) Right: all three contribute to warming.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.