Climate Change: UPSC Previous Year Questions (Environment and Ecology)
30 previous year UPSC Prelims questions on climate change appear here, from 2008 to 2025. The 2025 paper alone asked about cement emissions, COP28, Article 6, Direct Air Capture, per capita emissions and wet-bulb temperatures. UPSC also asks about carbon markets, geoengineering ideas and forest declarations. The explanations give the mechanism and the institution behind each.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 11–20 of 30 questions
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UPSC 2019Environment and Ecology · Climate Change
Q11. In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulphate aerosol into the stratosphere?
Explanation
There is a renewed interest in two dominant methods of geoengineering such as stratospheric sulphate aerosol increase and cirrus cloud thinning aims to reduce global warming effects. Geoengineering, often known as climate intervention, is the deliberate and extensive modification of the Earth’s climatic system with the intention of reducing global warming. The stratosphere can be injected with sulphate aerosol particles to block some of the sun’s rays and possibly cool the planet. Sulphur droplets are good at scattering the sun’s light back out into space and it does not heat the stratosphere as much as other aerosols.
UPSC 2019Environment and Ecology · Climate Change
Q12. Consider the following statements: 1. Agricultural soils release nitrogen oxides into the environment. 2. Cattle release ammonia into the environment. 3. Poultry industry releases reactive nitrogen compounds into the environment. Which of the statements given above is/are correct?
Explanation
As per the Indian Nitrogen Assessment report, 2017, the share of agriculture in total GHG emissions has gradually declined from 28% in 1994 to 14% in 2016. Agricultural emissions in India are primarily from the livestock sector (54.6%) and the use of nitrogenous fertilizers (19%). Rice cultivation in anaerobic conditions accounts for a major portion of agricultural emissions (17.5%).
Statement 1 is correct: Agricultural soils release nitrogen oxides into the environment Fertilizers (especially nitrogen-based like urea) lead to the emission of nitrous oxide (N₂O), a greenhouse gas. Microbial processes such as nitrification and denitrification release NO, NO, and NO.
Statement 2 is correct: Cattle release ammonia into the environment Cattle excrete urea in urine, which breaks down into ammonia (NH₃) through microbial action. Livestock farming is a major contributor to ammonia emissions.
Statement 3 is correct: Poultry industry releases reactive nitrogen compounds into the environment Poultry litter (manure, bedding material, and feed waste) contains nitrogen compounds that can convert into ammonia, nitrates, and nitrites. This contributes to air and water pollution.
UPSC 2019Environment and Ecology · Climate Change
Q13. In the context of proposals to the use of hydrogen-enriched CNG (H-CNG) as fuel for buses in public transport, consider the following statements: 1. The main advantage of the use of H-CNG is the elimination of carbon monoxide emissions. 2. H-CNG as fuel reduces carbon dioxide and hydrocarbon emissions. 3. Hydrogen up to one-fifth by volume can be blended with CNG as fuel for buses. 4. H-CNG makes the fuel less expensive than CNG. Which of the statements given above is/are correct?
Explanation
Hydrogen-enriched CNG (H-CNG) is a blended gas. It is produced by mixing hydrogen with CNG. HCNG reduces emissions of CO up to 70% and engines can be calibrated to release lower amounts of NO. enables up to 5 % savings in fuel. It can be the first step towards the future Hydrogen economy. It gives better performance due to higher Octane rating of H2.
Statement 1 is incorrect: HCNG doesn’t eliminate but reduces emissions of CO up to 70%.
Statement 2 is correct: It can be used in place of gasoline, diesel fuel and propane (C3H8) / LPG and its combustion produces fewer undesirable gases.
Statement 3 is correct: The blending of hydrogen with CNG provides a blended gas termed as HCNG. Also, the ideal Hydrogen concentration is close to 20 %. It can prove to be the ideal fuel for heavy-duty vehicles and applications with high loads.
Statement 4 is incorrect: The current cost of Hydrogen is more than the cost of Natural Gas. So, HCNG’s cost is more than CNG.
Exam tip:
When S2 says "Reduces", then, isn’t S1’s "Elimination of CO" an extreme phrase, hence S1 is more probable to be false, Also, what do you think is more practical and logical: Elimination or Reducing? Clearly Second one hence S1 false and S2 true giving option B as correct.
UPSC 2017Environment and Ecology · Climate Change
Q14. 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:
Explanation
Carbon Sequestration is a process to capture and store CO₂ to curb global warming. It is captured from the air, industries or power stations and stored permanently underground. Terrestrial Carbon Sequestration is the process through which CO₂ from the atmosphere is absorbed by trees and plants through photosynthesis and stored as carbon in soils and biomass (tree trunks, branches, foliage, and roots). In Geologic Carbon Sequestration CO₂ can be stored in oil reservoirs, gas reservoirs, unmineable coal seams, saline formations and shale formations with high organic content.
Statement 1 is correct: Uneconomic coal seams can be used to store CO₂ because the CO₂ molecules attach to the surface of coal.
Statement 2 is correct: CO₂ is sometimes injected into declining oil fields to increase oil recovery.
Statement 3 is correct: Other potential sites are gas reservoirs, saline formations and shale formations with high organic content.
UPSC 2016Environment and Ecology · Climate Change
Q15. The term ‘Intended Nationally Determined Contributions’ is sometimes seen in the news in the context of
Explanation
Intended Nationally Determined Contributions (IN-DCs) are planned reductions in greenhouse gas emissions outlined by countries under the United Nations Framework Convention on Climate Change (UNFCCC). NDCs are at the heart of the Paris Agreement and embody efforts by each country to reduce national emissions and adapt to the impacts of climate change. The UNFCCC, in its Nationally Determined Contributions (NDC) Synthesis Report, has called for more ambitious climate action plans by the countries in order to achieve the Paris Agreement target of containing global temperature rise to 2°C by the end of the century (ideally it is 1.5°C).
UPSC 2016Environment and Ecology · Climate Change
Q16. What is ‘Greenhouse Gas Protocol’?
Explanation
GHG Protocol is developing standards, tools and online training that helps countries to measure and manage greenhouse gas (GHG) emissions from private and public sector operations, value chains and mitigation actions. The GHG Protocol arose when the World Resources Institute (WRI) and World Business Council for Sustainable Development (WBCSD) recognized the need for an international standard for corporate GHG accounting and reporting in the late 1990s.
UPSC 2014Environment and Ecology · Climate Change
Q17. The scientific view is that the increase in global temperature should not exceed 2°C above the 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. The 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:
Explanation
Statement 1 is correct: If the global temperature increases beyond 3 “C above the pre-industrial level, the terrestrial biosphere will tend towards being a net carbon source. Taiga and temperate forests act as an important carbon sink that would turn into a carbon source.
Statement 2 is correct: As temperatures rise, mass coral bleaching events occur. If the temperature keeps on rising, widespread coral mortality will occur.
Statement 3 and 4 are incorrect: The temperate regions can still survive if the temperature increases. The temperate zones are where the widest seasonal changes occur. The vegetation can survive there. The weather should be warm and moist during the early stage of the growth of cereals. Therefore, the cultivation of cereals would still be possible if the temperature rises.
UPSC 2013Environment and Ecology · Climate Change
Q18. With reference to the usefulness of the byproducts of the sugar industry, which of the following statements is/are correct? 1. Bagasse can be used as biomass fuel for the generation of energy. 2. Molasses can be used as one of the feedstocks for the production of synthetic chemical fertilizers. 3. Molasses can be used for the production of ethanol. Select the correct answer using the codes given below:
Explanation
Bagasse and Molasses:
Introduction Uses Bagasse is the remnant left after extracting the juice of the sugarcane or sorghum is known as bagasse. It is a dry pulpy fibrous material. It is used for the generation of heat energy and electricity. Ethanol produced from it is also used as a popular fuel in some countries. It substitutes wood to produce pulp, paper, and board. As a cattle feed when mixed with molasses and enzymes and then fermenting. Molasses is the thick syrup that results from the refining of sugarcane or sugar beets into sugar. It contains a good amount of Vitamin B6 and minerals like calcium, manganese, iron and magnesium. Sweetening and flavouring foods. In the production of fine commercial brown sugar. In baking and cooking. Producing ethanol and is the prime ingredient in the distillation of few alcoholic beverages. As a cattle feed. Statements 1 and 3 are correct: Bagasse can be used for the generation of heat energy and electricity. Molasses can be used for the production of ethanol and it is also used as the ingredient in the distillation of a few alcoholic beverages.
Statement 2 is incorrect: Molasses is not used for the production of chemical fertilizers. Synthetic fertilizers are typically made from chemical compounds like ammonia, urea, and phosphates, which are derived from petrochemicals or mineral sources. Molasses is rich in sugars and organic matter which make it unsuitable for the production of synthetic fertilizers.
UPSC 2012Environment and Ecology · Climate Change
Q19. Consider the following statements: Chlorofluorocarbons, known as ozone-depleting substances, are used: 1. In the production of plastic foams. 2. In the production of tubeless tyres. 3. In cleaning certain electronic components. 4. As pressurizing agents in aerosol cAns: Which of the statements given above is/are correct?
Explanation
Chlorofluorocarbons, Hydrochlorofluorocarbons, Carbon tetrachloride, Methyl chloroform, Methyl chloroform, Ha-lons, Methyl bromide, etc. are Ozone Depleting Substances. Chlorofluorocarbons (CFCs) also referred to as ozone depleting materials, are used to make plastic foams, cleaning electronic components, and pressurising aerosol cAns: They are non-toxic, nonflammable chemicals containing atoms of carbon, chlorine and fluorine. Statements 1, 3 and 4 are correct: Chlorofluorocarbons, known as ozone-depleting substances, are used in the production of plastic foams, in cleaning electronic components, and as pressurising agents in aerosol.
Statement 2 is incorrect: Chlorofluorocarbons are not used in the production of tubeless tyres. Tubeless tyre is basically a clincher tyre inflated onto a rim with no inner tube. Instead of an inner tube holding the air pressure, an airtight chamber is created with a tubeless-specific tyre, developed with a special (commonly carbon) bead, and a compatible rim.
UPSC 2012Environment and Ecology · Climate Change
Q20. The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs
Explanation
Greenhouse Effect is a naturally occurring phenomenon that warms and covers the lower atmosphere of the planet, keeping it at a temperature where life may survive. The earth’s cooling and warming are balanced by them. Without this, the current 15 degrees Celsius average temperature of the earth’s surface would be -19 degrees Celsius. Human-induced greenhouse gas emissions upset the natural balance & lead to increased warmth.
Option (d) is correct: Carbon dioxide absorbs the infrared (IR) radiation emitted by the Earth’s surface. When sunlight reaches the Earth it warms the surface, which then re-emits this energy as infrared radiation. CO₂ molecules absorb this IR radiation, trapping heat in the atmosphere and causing the temperature to rise.The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere because it absorbs the infrared part of the solar radiation. It absorbs energy with a wavelength of 15 m (micrometres).
Answer key for these questions
Q
UPSC year
Correct answer
11
2019
(d) Reducing the global warming
12
2019
(d) 1, 2 and 3
13
2019
(b) 2 and 3 only
14
2017
(d) 1, 2 and 3
15
2016
(b) plan of action outlined by the countries of the world to combat climate change
16
2016
(a) It is an international accounting tool for government and business leaders to understand, quantify and manage greenhouse gas emissions.
17
2014
(b) 1 and 2 only
18
2013
(c) 1 and 3 only
19
2012
(c) 1, 3 and 4 only
20
2012
(d) The infrared part of the solar radiation.
What UPSC has tested in Climate Change
Article 6 of the Paris Agreement deals with carbon markets and cooperative approaches between countries.
Direct Air Capture extracts carbon dioxide directly from the atmosphere and can be used for carbon sequestration.
Cirrus cloud thinning is suggested by some scientists as a way of reducing the global warming.
Climate Action Tracker is a database created by climate research organisations that monitors countries’ emission pledges.
The World Bank has warned that India could become one of the first places where wet-bulb temperatures exceed human tolerance.
Frequently asked questions
How many previous year UPSC questions are there on Climate Change?
This page covers 30 previous year UPSC Prelims GS Paper-I questions on Climate Change (Environment and Ecology), asked from 2008 to 2025. Each has the correct answer and an explanation.
What does Article 6 of the Paris Agreement cover?
Voluntary cooperation between countries to meet their climate targets, including carbon markets in which emission reductions can be traded and used toward national contributions, along with non-market approaches.
What is Direct Air Capture?
A technology that removes carbon dioxide directly from the ambient air using chemical solvents or solid sorbents. The captured carbon can be stored underground or used in fuels and products, so it can help cut atmospheric carbon.
What is a wet-bulb temperature?
A measure that combines heat and humidity. When the wet-bulb temperature approaches 35 °C, the human body can no longer cool itself by sweating, so even healthy people can die within hours without relief.
