UPSC Prelims 2011 · GS Paper I

Question 9: Environment and Ecology

The formation of ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole ?

aPresence of prominent tropospheric turbulence; and inflow of chlorofluorocarbons

bPresence of prominent polar front and stratospheric clouds; and inflow of chlorofluorocarbons

cAbsence of polar front and stratospheric clouds; and inflow of methane and chlorofluorocarbons

dIncreased temperature at polar region due to global warming

AnswerThe answer is (b).

The Antarctic ozone hole forms in the southern spring. In winter a strong polar circulation (the polar vortex, the option's 'polar front') isolates the air over Antarctica, and it becomes extremely cold, so polar stratospheric clouds form. Ice crystals on these clouds convert chlorine from chlorofluorocarbons into reactive forms, and returning sunlight then destroys ozone quickly. So the causes are the polar circulation with stratospheric clouds, and CFCs. Remember: cold, clouds, chlorine.

Why each option is right or wrong

(a) Tropospheric turbulence plays no role; the ozone loss happens in the stratosphere.
(b) Right: polar stratospheric clouds with the polar circulation, and inflow of CFCs.
(c) The clouds and polar front are present, not absent; methane is not the cause.
(d) The polar stratosphere is extremely cold, not warm, and that cold allows the clouds to form.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.