Climate Change — Ecology & Environment

Q.1

WBCS Prelims 2009

Greenhouse effect is caused by addition of too much of this compound in atmosphere.

A. Carbon di-oxide

B. Ammonia

C. Water vapour

D. Dust particles

Explanation

Why Correct: Carbon dioxide (CO2) is the primary anthropogenic greenhouse gas driving enhanced greenhouse effect through fossil fuel combustion and deforestation, trapping infrared radiation.
Distractor Analysis: Ammonia (NH3) is a reactive nitrogen compound from agriculture that contributes to air pollution and eutrophication, not significant greenhouse warming. Water vapor is a natural greenhouse gas whose concentration depends on temperature feedbacks, not directly added by human activities. Dust particles (aerosols) can reflect sunlight and have cooling effects, though black carbon soot contributes to warming.
Takeaway: Methane (CH4) is the second most important anthropogenic greenhouse gas, with 28 times the warming potential of CO2 over 100 years.

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Q.2

WBCS Prelims 2008

The Greenhouse effect gases trap only the heat of following radiations:

A. Ultraviolet

B. Infrared

C. Solar

D. Both (A) and (B)

Explanation

Why Correct: Greenhouse gases like CO2, methane, and water vapor absorb and re-emit outgoing longwave infrared radiation, trapping heat in the atmosphere.
Distractor Analysis: Ultraviolet radiation is mostly absorbed by the ozone layer and does not directly contribute to greenhouse heating. Solar radiation includes the full spectrum of incoming shortwave radiation, but greenhouse gases specifically trap the infrared portion after Earth's surface re-radiates it.
Takeaway: The natural greenhouse effect maintains Earth's average temperature at about 15°C; without it, the temperature would be around -18°C.

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Q.3

WBCS Prelims 2007

Which one of the four following substances contribute most of the causation of greenhouse effect in nature?

A. Carbon di-oxide

B. Hydrogen fluoride

C. Carbon monoxide

D. Sulphur di-oxide

Explanation

Why Correct: Carbon dioxide (CO2) accounts for approximately 76% of the total anthropogenic greenhouse effect, making it the dominant contributor among human-caused greenhouse gases.
Distractor Analysis: Hydrogen fluoride is a toxic industrial gas with minimal atmospheric presence and negligible greenhouse impact. Carbon monoxide is primarily an air pollutant that indirectly affects climate by influencing atmospheric chemistry but has weak direct radiative forcing. Sulphur dioxide contributes to aerosol formation and cooling effects rather than greenhouse warming.
Takeaway: Methane (CH4) is the second most significant greenhouse gas at about 16% of total forcing, followed by nitrous oxide (N2O) at 6% and fluorinated gases at 2%.

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