UPSC CSE Prelims
Climate Change and Mitigation Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Climate Change and Mitigation
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Which of the following statements are correct about the deposits of ‘methane hydrate’?
- Global warming might trigger the release of methane gas from these deposits.
- Large deposits of ‘methane hydrate’ are found in Arctic Tundra and under the seafloor.
- Methane in atmosphere oxidizes to carbon dioxide after a decade or two.
Select the correct answer using the code given below:
Detailed Explanation:
Answer: Option 4 — 1, 2 and 3
All three statements about methane hydrate deposits are correct. Methane hydrates are ice-like structures that trap methane and are vulnerable to release under warming conditions, creating a potential climate feedback loop.
✅ Statement 1 – Correct: Global warming can destabilize methane hydrate deposits in permafrost and ocean sediments, triggering methane release—a potent greenhouse gas that amplifies warming.
✅ Statement 2 – Correct: Large methane hydrate reserves are found in Arctic tundra permafrost and in deep-sea sediments along continental margins.
✅ Statement 3 – Correct: Methane in the atmosphere oxidizes to carbon dioxide through hydroxyl radical reactions after approximately 12 years, though CO₂ persists much longer in the atmosphere.
📝 Short Notes: Methane Hydrates
- Structure: Ice-like crystalline solids where methane molecules are trapped within water molecule cages, stable under high pressure and low temperature.
- Major Locations: Arctic permafrost regions and seafloor sediments on continental margins (300-500m depth), particularly offshore India (Krishna-Godavari basin).
- Climate Risk: Methane is 25-30 times more potent as a greenhouse gas than CO₂ over a 100-year period; release creates positive feedback loop.
- Oxidation Process: Atmospheric methane oxidizes via hydroxyl radicals (OH) to CO₂ with an average lifetime of ~12 years.
- Potential Resource: Estimated global reserves exceed conventional natural gas; India conducted successful extraction trial in 2019.
- Destabilization Triggers: Rising ocean temperatures, pressure changes, and permafrost thawing can release stored methane.
In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulphate aerosols into the stratosphere?
Detailed Explanation:
Answer: Option 4 — Reducing global warming
Both cirrus cloud thinning and stratospheric sulphate aerosol injection are proposed geoengineering techniques aimed at mitigating climate change. Cirrus clouds trap infrared radiation similar to greenhouse gases; thinning them would reduce heat retention. Sulphate aerosols in the stratosphere reflect incoming solar radiation back into space, thereby cooling the planet.
📝 Short Notes: Geoengineering Techniques for Climate Mitigation
| Technique | Mechanism | Purpose |
|---|---|---|
| Cirrus Cloud Thinning | Thinning high-altitude cirrus clouds reduces their ability to trap outgoing infrared radiation | Reduce atmospheric heat retention and global warming |
| Stratospheric Aerosol Injection | Injecting reflective sulphate aerosol particles into the stratosphere to reflect sunlight back into space | Reduce incoming solar radiation and cool the planet |
| Marine Cloud Brightening | Spraying seawater into low-lying clouds to increase their reflectivity | Increase albedo effect and reflect more sunlight |
| Ocean Iron Fertilization | Adding iron to oceans to stimulate phytoplankton growth for CO₂ absorption | Enhance carbon sequestration |
- Solar Radiation Management (SRM): Techniques like aerosol injection and cloud modification aim to reflect sunlight and reduce heat absorption.
- Carbon Dioxide Removal (CDR): Techniques focus on removing CO₂ from the atmosphere through biological or chemical means.
- Concerns: Geoengineering techniques have potential side effects including disruption of precipitation patterns, ozone depletion, and unknown long-term consequences.
- Governance: International frameworks and ethical considerations are essential before large-scale deployment of geoengineering solutions.
Which of the following statements best describes "carbon fertilization"?
Detailed Explanation:
Answer: Option 1 — Increased plant growth due to increased concentration of carbon dioxide in the atmosphere
Carbon fertilization refers to the phenomenon where elevated atmospheric CO₂ concentrations enhance the rate of photosynthesis in plants, leading to increased plant growth and biomass production. Since CO₂ is a key substrate for photosynthesis, higher concentrations allow plants to synthesize more sugars (glucose), thereby accelerating growth rates. This effect is distinct from global warming (temperature increase), ocean acidification, or adaptive responses to climate change.
📝 Short Notes: Carbon Fertilization and Plant Physiology
- Carbon Fertilization: The enhancement of photosynthetic rates and plant growth due to elevated atmospheric CO₂ levels.
- Photosynthesis Basics: Plants absorb CO₂, water, and sunlight to produce glucose (C₆H₁₂O₆) and release oxygen (O₂) as a byproduct.
- Current CO₂ Levels: Atmospheric CO₂ concentration has reached approximately 420 ppm (as of recent measurements), the highest in millions of years, primarily due to fossil fuel combustion and deforestation.
- Growth Response: Many C3 plants (wheat, rice, soybeans) show significant growth enhancement with increased CO₂, though C4 plants (maize, sugarcane) show less response.
- Limitations: Carbon fertilization benefits are limited by other factors like nutrient availability (nitrogen, phosphorus), water stress, and temperature extremes.
- Ecosystem Impacts: While increased plant growth may sequester more carbon, this effect is offset by increased respiration, decomposition, and other climate change impacts.
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In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the potential sites for carbon sequestration?
- Abandoned and uneconomic coal seams
- Depleted oil and gas reservoirs
- Subterranean deep saline formations
Select the correct answer using the code given below:
Detailed Explanation:
Answer: Option 4 — 1, 2 and 3
All three options represent viable geological sites for carbon sequestration, which is the process of capturing and storing atmospheric carbon dioxide to mitigate global warming. These geological formations possess the necessary characteristics—porosity, permeability, and secure cap rocks—to safely store CO₂ underground for extended periods.
✅ Statement 1 – Correct: Abandoned and uneconomic coal seams can store CO₂ through a process called coal seam carbon sequestration, where CO₂ is adsorbed onto the coal matrix, potentially displacing methane in the process.
✅ Statement 2 – Correct: Depleted oil and gas reservoirs are proven storage sites as they have already trapped hydrocarbons for millions of years, indicating their capacity to securely contain injected CO₂ with existing infrastructure.
✅ Statement 3 – Correct: Subterranean deep saline formations (aquifers) are among the most promising and abundant carbon storage sites globally, offering vast storage capacity far below freshwater resources with minimal environmental risk.
With reference to the Agreement at the UNFCCC Meeting in Paris in 2015, which of the following statements is/are correct?
- The Agreement was signed by all the member countries of the UN and it will go into effect in 2017.
- The Agreement aims to limit greenhouse gas emissions so that the rise in average global temperature by the end of this century does not exceed 2 degrees C or even 1.5 degrees C above pre-industrial levels.
- Developed countries acknowledged their historical responsibility in global warming and committed to donate $1000 billion a year from 2020 to help developing countries to cope with climate change.
Select the correct answer using the code given below.
Detailed Explanation:
Answer: Option 2 — 2 only
❌ Statement 1 – Incorrect: The Paris Agreement was adopted in December 2015 and signed in April 2016, but it entered into force on November 4, 2016 (not 2017) after 55 countries representing at least 55% of global emissions ratified it. Moreover, it was not signed by all UN member countries.
✅ Statement 2 – Correct: The Paris Agreement's central aim is to strengthen the global response to climate change by keeping the global temperature rise this century well below 2°C above pre-industrial levels and pursuing efforts to limit the increase to 1.5°C.
❌ Statement 3 – Incorrect: While developed countries acknowledged their historical responsibility under the principle of Common But Differentiated Responsibilities and Respective Capabilities (CBDR-RC), the financial commitment was $100 billion per year by 2020, not $1000 billion.
The term ‘Intended Nationally Determined Contribution’ is sometimes seen in the news in the context of:
Detailed Explanation:
Answer: Option 2 — Plan of action outlined by the countries of the world to combat climate change.
Intended Nationally Determined Contributions (INDCs) are voluntary climate action plans submitted by countries before the Paris Agreement (2015). Each nation outlined its intended contributions to reduce greenhouse gas emissions, transition to renewable energy, and adapt to climate impacts based on its national circumstances and capabilities. Once countries ratified the Paris Agreement, these INDCs became Nationally Determined Contributions (NDCs) — the cornerstone of the global climate framework. They follow a bottom-up approach where countries independently determine their targets rather than having them imposed internationally.
Which of the following best describes the aim of ‘Green India Mission’ of the Government of India?
- Incorporating environment benefits and costs into the Union and State Budgets thereby implementing the ‘green accounting’.
- Launching the second green revolution to enhance agriculture output so as to ensure food security to one and all in the future.
- Restoring and enhancing forest cover and responding to climate change by a combination of adaptation and mitigation measures.
Select the correct answer using the code given below
Detailed Explanation:
Answer: Option 3 — 3 only
❌ Statement 1 – Incorrect: Green accounting refers to incorporating environmental costs and benefits into national budgets, which is a separate economic initiative. The Green India Mission does not aim at implementing green accounting in Union and State budgets.
❌ Statement 2 – Incorrect: The Second Green Revolution focuses on enhancing agricultural productivity and food security. The Green India Mission, part of the National Action Plan on Climate Change (NAPCC), specifically targets forestry and forest cover, not agricultural output.
✅ Statement 3 – Correct: The National Mission for a Green India (GIM) aims to protect, restore, and enhance India's forest cover while responding to climate change through adaptation and mitigation measures. It targets increasing forest cover on 5 million hectares and improving quality on another 5 million hectares, thereby enhancing ecosystem services including carbon sequestration and biodiversity conservation.
What is ‘Greenhouse Gas Protocol’?
Detailed Explanation:
Answer: Option 1 — It is an international accounting tool for government and business leaders to understand, quantify and manage greenhouse gas emissions
The Greenhouse Gas Protocol is the most widely used global framework for measuring and managing greenhouse gas emissions. Developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD), it provides standardized methods for organizations and governments to account for their carbon footprint. It is not a UN financial initiative, not a legally binding intergovernmental agreement, and not related to REDD+ initiatives hosted by the World Bank.
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?
- Terrestrial biosphere tends toward a net carbon source
- Widespread coral mortality will occur.
- All the global wetlands will permanently disappear.
- Cultivation of cereals will not be possible anywhere in the world.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Beyond 3°C warming, ecosystem tipping points like forest dieback and permafrost thaw cause the terrestrial biosphere to shift from carbon sink to carbon source, releasing more CO₂ than absorbed.
✅ Statement 2 – Correct: Coral reefs face 99% loss at 2°C warming; at 3°C, widespread coral mortality becomes catastrophic and irreversible globally.
❌ Statement 3 – Incorrect: The term "all wetlands" and "permanently disappear" is extreme; many wetlands would be severely degraded or lost, but complete global disappearance is scientifically implausible.
❌ Statement 4 – Incorrect: The term "anywhere in the world" is an overstatement; while cereal cultivation would face severe disruption and crop failures, high-latitude regions might still support limited production.
If the National Water Mission is properly and completely implemented, how will it impact the country?
- Part of the water needs of urban areas will be met through recycling of wastewater.
- The water requirements of coastal cities with inadequate alternative sources of water will be met by adopting appropriate technologies that allow for the use of ocean water.
- All the rivers of Himalayan origin will be linked to the rivers of peninsular India.
- The expenses incurred by farmers for digging bore-wells and for installing motors and pump sets to draw groundwater will be completely reimbursed by the Government.
Select the correct answer using the codes given below:
Detailed Explanation:
✅ Statement 1 – Correct: The National Water Mission (NWM) explicitly includes urban water recycling and reuse as a key strategy to meet part of the water needs of urban areas and reduce dependency on freshwater sources.
✅ Statement 2 – Correct: The NWM promotes adoption of desalination technologies for coastal cities facing water scarcity, particularly where alternative freshwater sources are inadequate.
❌ Statement 3 – Incorrect: The interlinking of rivers is a separate project under the National Perspective Plan, not part of the NWM's mandate, which focuses on water conservation and efficient use.
❌ Statement 4 – Incorrect: The NWM emphasizes sustainable groundwater management and promotes efficiency, but does not include financial reimbursement schemes for farmers' bore-well and pump-set expenses.
The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere because it absorbs -
Detailed Explanation:
Carbon dioxide (CO₂) and other greenhouse gases absorb infrared radiation (heat) emitted by Earth's surface after it absorbs solar energy.
This trapped infrared radiation causes the greenhouse effect, gradually raising atmospheric temperature—not UV or all solar radiation, but specifically the long-wave infrared re-radiated from Earth.
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