UPSC Environment and Ecology – Chapter 18: Climate Change – Science and Impacts (28 MCQs)

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UPSC Environment and Ecology – Chapter 18: Climate Change – Science and Impacts (28 MCQs) – 28 questions, subject: Environment. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  

Greenhouse gases warm the Earth mainly by absorbing:

Correct Answer: D [long-wave terrestrial radiation]

Explanation:

Greenhouse gases absorb the long-wave infrared radiation emitted by the warmed surface and re-emit part of it downward.

2.  

According to IPCC AR6, the 100-year global warming potential of nitrous oxide is about:

Correct Answer: B [273]

Explanation:

IPCC AR6 gives nitrous oxide a 100-year global warming potential of 273 relative to carbon dioxide.

3.  

According to the WMO, the global average CO₂ concentration in 2025 was about:

Correct Answer: C [427 ppm]

Explanation:

426.8 ppm.

4.  

The first calendar year in which the global average temperature exceeded 1.5 °C above pre-industrial was:

Correct Answer: D [2024]

Explanation:

The WMO found 2024 about 1.55 °C above the 1850–1900 average, the first calendar year above 1.5 °C.

5.  

According to the WMO, the global mean temperature in 2025 was about how much above 1850–1900?

Correct Answer: A [1.44 °C]

Explanation:

The WMO's consolidated analysis of 14 January 2026 put 2025 at 1.44 °C ± 0.13 °C above the 1850–1900 average.

6.  

The IPCC was set up in 1988 by:

Correct Answer: A [WMO and UNEP]

Explanation:

The World Meteorological Organization and the UN Environment Programme jointly established the IPCC in 1988.

7.  

Melting ice exposing darker surfaces that absorb more heat is an example of:

Correct Answer: C [ice–albedo feedback]

Explanation:

Melting ice exposes darker land or sea that absorbs more sunlight, amplifying warming – the ice–albedo feedback.

8.  

Ocean acidification is caused mainly by:

Correct Answer: A [dissolution of atmospheric CO₂ in sea water]

Explanation:

Sea water absorbs atmospheric CO₂, forming carbonic acid that lowers the ocean's pH.

9.  

Which of the following short-lived climate pollutants is a particle rather than a gas?

Correct Answer: C [Black carbon]

Explanation:

Black carbon is soot, a particle from incomplete combustion, whereas methane, HFCs and tropospheric ozone are gases.

10.  

According to the MoES assessment of 2020, India's average temperature rose during 1901–2018 by about:

Correct Answer: B [0.7 °C]

Explanation:

The MoES assessment of 2020 found India's average temperature rose by about 0.7 °C during 1901–2018.

11.  

Assertion (A): High wet-bulb temperatures are dangerous for human survival.

Reason (R): In very humid heat, the body cannot shed heat effectively through the evaporation of sweat.

Correct Answer: A [Both A and R are true, and R is the correct explanation of A]

Explanation:

At high wet-bulb temperatures sweat cannot evaporate well, so the body cannot cool itself; R explains why A is dangerous.

12.  

Which of the following has the longest lifetime in the atmosphere?

Correct Answer: B [Sulphur hexafluoride]

Explanation:

thousands of years.

13.  

The Paris Agreement's 1.5 °C limit refers to:

Correct Answer: D [long-term warming averaged over about 20 years]

Explanation:

The Paris 1.5 °C limit refers to long-term global warming, averaged over about 20 years, not to single months or years.

14.  

Stratospheric aerosol injection is proposed as a method to:

Correct Answer: D [reduce global warming]

Explanation:

a geo-engineering idea.

15.  

The 11 warmest years on record, according to the WMO, are:

Correct Answer: C [2015–2025]

Explanation:

The WMO confirmed on 14 January 2026 that 2015–2025 were the eleven warmest years in all eight datasets.

16.  

Continuous measurement of atmospheric CO₂ at Mauna Loa began in:

Correct Answer: B [1958]

Explanation:

Charles Keeling.

17.  

Arrange in chronological order:

1. IPCC Special Report on 1.5 °C
2. IPCC set up
3. IPCC AR6 Synthesis Report
4. First calendar year above 1.5 °C

Select the correct order:

Correct Answer: C [2-1-3-4]

Explanation:

1988, 2018, 2023, 2024.

18.  

India's largest source of CO₂ emissions is:

Correct Answer: D [electricity and heat production]

Explanation:

Coal-based electricity and heat production is the largest source of India's CO₂ emissions.

19.  

The Gulf of Mannar is vulnerable to climate change mainly through:

Correct Answer: B [coral bleaching during marine heatwaves]

Explanation:

The Gulf of Mannar's coral reefs bleach when marine heatwaves keep sea temperatures too high for too long.

20.  

Consider the following about methane:

1. It is more powerful than CO₂ per tonne over 100 years.
2. It stays in the atmosphere for about a decade.
3. It is not produced by livestock.

Which of the statements given above are correct?

Correct Answer: B [1 and 2 only]

Explanation:

Methane has a 100-year GWP of about 27–30 and lasts about a decade; livestock is a major source, so 3 is false.

21.  
UPSC Prelims 2025

Consider the following statements:

I. Carbon dioxide (CO2) emissions in India are less than 0.5 t CO2/capita.

II. In terms of CO2 emissions from fuel combustion, India ranks second in the Asia-Pacific region.

III. Electricity and heat producers are the largest sources of CO2 emissions in India.

Which of the statements given above is/are correct?

Correct Answer: C [II and III only]

Explanation:

India emits about 2 t CO₂ per person; it ranks second in the Asia–Pacific, and power and heat producers lead its emissions.

22.  
UPSC Prelims 2024

Consider the following statements:

Statement-I: The atmosphere is heated more by incoming solar radiation than by terrestrial radiation.

Statement-II: Carbon dioxide and other greenhouse gasses in the atmosphere are good absorbers of long wave radiation.

Which one of the following is correct in respect of the above statements ?

Correct Answer: D [Statement-I is incorrect, but Statement-II is correct]

Explanation:

Greenhouse gases absorb long-wave terrestrial radiation, so the atmosphere is heated more by the Earth than by incoming sunlight.

23.  
UPSC Prelims 2022

Among the following crops, which one is the most important anthropogenic source of both methane and nitrous oxide ?

Correct Answer: B [Rice]

Explanation:

Flooded paddies emit methane, and fertilised rice soils, especially under alternate wetting and drying, emit nitrous oxide.

24.  
UPSC Prelims 2022

Consider the following statements:

1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
2. Low clouds have a high absorption of infrared radiation emanating from the Earth's surface and thus cause a warming effect.

Which of the statements given above is/are correct?

Correct Answer: D [Neither 1 nor 2]

Explanation:

High thin clouds mainly warm by trapping infrared and low thick clouds mainly cool by reflecting sunlight, so both statements are reversed.

25.  
UPSC Prelims 2019

Which of the following statements are correct about the deposits of 'methane hydrate'?

1. Global warming might trigger the release of methane gas from these deposits.
2. Large deposits of 'methane hydrate' are found in Arctic Tundra and under the seafloor.
3. Methane in the atmosphere oxidised to carbon dioxide after a decade or two.

Select the correct answer using the code given below.

Correct Answer: D [1, 2 and 3]

Explanation:

Hydrates in the tundra and sea floor could release methane with warming, and atmospheric methane oxidises to CO₂ in a decade or two.

26.  
UPSC Prelims 2018

Which of the following statements best describes "carbon fertilisation"?

Correct Answer: A [Increased plant growth due to increased concentration of carbon dioxide in the atmosphere]

Explanation:

Carbon fertilisation is the increase in plant growth caused by a higher concentration of CO₂ in the atmosphere.

27.  
UPSC Prelims 2017

In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be potential sites for carbon sequestration?

1. Abandoned and uneconomic coal seams
2. Depleted oil and gas reservoirs
3. Subterranean deep saline formations

Select the correct answer using the code given below:

Correct Answer: D [1, 2 and 3]

Explanation:

Uneconomic coal seams, depleted oil and gas reservoirs and deep saline formations can all store injected CO₂ underground.

28.  
UPSC Prelims 2014

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:

Correct Answer: B [1 and 2 only]

Explanation:

Beyond 3 °C the terrestrial biosphere tends to become a net carbon source and widespread coral mortality occurs; 3 and 4 are exaggerations.

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