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Subject: Environment

  • Davis Strait Proto-Microcontinent

    Why in the News?

    A hidden landmass, called the Davis Strait proto-microcontinent, has been discovered beneath the icy waters between Canada’s Baffin Island and Greenland.

    About the Davis Strait Proto-Microcontinent:

    • The Davis Strait Proto-Microcontinent is a hypothesised landmass located in the Davis Strait, believed to have existed during the Paleozoic era.
    • It is composed of 19–24 km thick thinned continental crust, surrounded by two narrow bands of 15–17 km thick continental crust.
    • It is thought to have broken apart due to tectonic movements.
    • Geological evidence, including similarities in rock formations and tectonic features found in Greenland and parts of the Canadian Arctic, supports the idea of this ancient landmass.
    • While its exact nature and extent remain debated, the proto-microcontinent is crucial for understanding the tectonic processes that shaped the Atlantic Ocean and surrounding regions.

    About Davis Strait:

    • The Davis Strait is a large body of water located between southeastern Baffin Island (Canada) and southwestern Greenland, serving as part of the Northwest Passage.
    • It separates the Baffin Bay (to the north) from the Labrador Sea (to the south), and it connects the Atlantic Ocean and Arctic Ocean through the Canadian Arctic Archipelago.
    • It is an important maritime route for shipping and trade.
    • Named after John Davis, the English explorer who navigated the area in the late 16th century, the Davis Strait plays a significant role in the tectonic evolution of the Arctic region.
    [UPSC 2013] Consider the following:

    (1). Electromagnetic radiation (2). Geothermal energy (3). Gravitational force (4). Plate movements (5). Rotation of the earth (6). Revolution of the earth

    Which of the above are responsible for bringing dynamic changes on the surface of the earth?

    Options: (a) 1 only (b) 2 and 3 only (c) 1, 2 and 3 (d) None*

     

  • [19th April 2025] The Hindu Op-ed: Steering the decarbonisation of India’s logistics sector

     

    PYQ Relevance:

    [UPSC 2013] Write a note on India’s green energy corridor to alleviate the problem of conventional energy.

    Linkage: Decarbonising the logistics sector necessitates a shift away from conventional energy sources. The development of a green energy corridor, as mentioned in this PYQ, is essential for supplying the renewable energy needed to power various aspects of logistics, such as electric trucks and warehouses

     

    Mentor’s Comment:  Viksit Bharat is a commitment to a stronger, self-reliant India by 2047, focusing on inclusive development. Achieving this requires a large, efficient, and future-ready logistics sector. While infrastructure and accessibility are key, prioritizing the environment is crucial. India’s carbon-heavy logistics must transform to meet net-zero emissions by 2070, reducing transportation, warehousing, and supply chain emissions for a sustainable future.

    Today’s editorial talks about India’s logistics sector, which creates a significant amount of carbon pollution. This topic is relevant for GS Paper 3 in the mains exam.

    _

    Let’s learn!

    Why in the News?

    India’s logistics sector, which produces a lot of carbon pollution, needs to change and become more eco-friendly.

    What role does logistics play in achieving Viksit Bharat 2047?

    • Enabler of Inclusive Development: Efficient logistics ensures that goods and services reach every corner of the country, promoting equitable growth across regions. Eg: Improved last-mile connectivity in remote areas boosts rural entrepreneurship and market access for farmers.
    • Driver of Economic Competitiveness: A streamlined logistics sector reduces costs and delays, enhancing India’s global trade competitiveness. Eg: The PM Gati Shakti initiative integrates infrastructure planning to speed up cargo movement and reduce logistics costs.
    • Catalyst for Sustainability and Resilience: Greener logistics support India’s net-zero targets and build climate-resilient infrastructure. Eg: Electrification of highways and promotion of rail freight reduce emissions from the transport sector.

    Why is urgent decarbonisation needed in road freight and warehousing?

    • High Share in Greenhouse Gas Emissions: Road freight alone contributes over 88% of transport emissions, with trucks accounting for 38% of CO₂ emissions (IEA 2023). Eg: A single heavy-duty diesel truck emits over 1,000 grams of CO₂ per km — multiplied across millions of trucks, this leads to massive environmental impact.
    • Dependence on Fossil Fuels: Road transport is highly dependent on oil combustion, making it one of the most carbon-intensive sectors. Warehouses often rely on non-renewable power sources like diesel generators for energy and refrigeration. Eg: India’s freight trucks mostly use diesel — a key factor in air pollution and rising import bills for crude oil.
    • Growing Demand Increases Future Emissions: With freight and warehousing demand expected to grow rapidly by 2030, emissions will rise unless green alternatives are adopted. Eg: Government plans to triple cargo movement on inland waterways and expand warehousing, which without clean tech would add significantly to GHG levels.
    • Missed Economic Opportunities without Green Shift: Decarbonisation can lead to cost savings, energy efficiency, and long-term competitiveness. Delay increases operational costs and reduces global trade alignment. Eg: Green warehouses with solar rooftops can reduce electricity costs by 20–30% and earn carbon credits.
    • Alignment with Net Zero and Global Climate Commitments: India has committed to Net Zero by 2070. Without decarbonising logistics, achieving this goal will be impossible. Eg: Transitioning to electric trucks and LNG-powered vessels supports global targets like the Paris Agreement and IMO’s shipping emission cuts.

    How can China and the U.S. guide India’s green freight transition?

    • Rail Freight as a Cleaner Alternative: China and the U.S. have shifted significant portions of freight transport from road to rail, which is more energy-efficient and low-carbon. Eg: China has heavily invested in rail infrastructure, making rail freight nearly 50% of its total freight, significantly reducing emissions compared to road transport.
    • Adoption of Cleaner Fuels and Technologies: Both countries have embraced electric rail systems and alternative fuels for freight, which India can adopt to decarbonise its logistics sector. Eg: The U.S. has invested in electrified rail corridors, and China has introduced LNG-powered freight trains, both of which reduce dependency on diesel and curb emissions.
    • Policy Support and Infrastructure Investment: China and the U.S. have implemented policy frameworks that incentivise green freight practices, such as tax breaks, green subsidies, and investment in sustainable infrastructure. Eg: China’s Green Freight initiative includes subsidies for green vehicles, while the U.S. offers funding for clean freight technology under programs like the Clean Diesel Program.

    Which steps has India taken to electrify freight and green maritime transport?

    • Western Dedicated Freight Corridor (WDFC): Spanning 1,506 km, the WDFC connects Delhi to Mumbai, facilitating high-speed, high-capacity freight movement. This electrified corridor supports double-stack container trains, enhancing efficiency and reducing emissions.
    • Subsidies for Electric Freight Vehicles: In 2024, India approved ₹5 billion to incentivise the adoption of electric trucks, aiming to replace polluting diesel vehicles. This initiative is part of a broader ₹109 billion scheme to promote electric vehicles across various sectors.
    • Investment in Green Maritime Infrastructure: India plans to allocate ₹25,000 crore towards developing green ports and shipping infrastructure. This includes building green hydrogen hubs and manufacturing eco-friendly vessels, supporting the transition to sustainable maritime practices.
    • Collaboration with Singapore: India is exploring the creation of a Green Digital Shipping Corridor with Singapore, aiming to link international ports and marine industries. This initiative focuses on reducing emissions and enhancing digital integration in maritime trade.
    • Harit Sagar Initiative: The ‘Harit Sagar Green Port Guidelines’ aim to integrate renewable energy into port operations, promote the use of green fuels, and modernise fleets. These guidelines are part of India’s strategy to achieve net-zero emissions in the maritime sector by 2070.

    Way forward: 

    • Enhance Green Infrastructure and Technology Adoption: India should accelerate investments in green technologies, such as electric trucks, renewable energy-powered warehouses, and cleaner maritime fuels, alongside expanding rail freight networks to further reduce carbon emissions.
    • Strengthen Policy Frameworks and International Collaborations: Strengthening government policies to incentivize sustainable logistics practices and fostering international partnerships, such as with Singapore for green shipping corridors, can help ensure the successful transition to a low-carbon logistics sector.

     

  • India to Headquarter the International Big Cat Alliance (IBCA) 

    Why in the News?

    India has signed a Headquarters Agreement with the International Big Cat Alliance (IBCA), officially establishing its headquarters in India.

    About International Big Cat Alliance (IBCA):

    • IBCA is a multi-country, multi-agency group of 96 big cat range and non-range countries focused on conserving 7 big cats and their habitats.
    • It was proposed by PM Modi in 2019, officially launched in April 2023 for Project Tiger’s 50th anniversary.
    • It aims to protect and conserve Tiger, Lion, Leopard, Snow Leopard, Cheetah, Jaguar, and Puma; restore habitats and reduce human-wildlife conflict.
    • Key activities include- Advocacy, knowledge sharing, eco-tourism promotion, and resource mobilization for big cat conservation.
    • Currently, India, Nicaragua, Eswatini, and Somalia are members. Though membership is open to 96 range countries with big cat habitats.
    • Governance: Includes a General Assembly, elected Council, and Secretariat with a Secretary-General.
    • India’s Role:
      • India is home to 5 (tiger, lion, leopard, snow leopard, and cheetah) of the 7 big cats and 70% of the world’s tiger population, playing a leading role in global wildlife protection.
      • ₹150 crore from the Indian government (2023-2028) with additional contributions from global partners.
    [UPSC 2024] Consider the following statements:

    1. Lions do not have a particular breeding season.

    2. Unlike most other big cats, cheetahs do not roar.

    3. Unlike male lions, male leopards do not proclaim their territory by scent marking.

    Which of the statements given above are correct?

    (a) 1 and 2 only * (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 2

     

  • Particulate Matter Emission Trading Scheme in Gujarat

    Why in the News?

    A new study highlights the success of Surat’s Particulate Matter Emission Trading Scheme (PM-ETS), the world’s first market-based system for trading particulate emissions.

    The scheme has reduced pollution by 20-30%, providing insights into its potential to improve air quality in industrial areas.

    About Particulate Matter Emission Trading Scheme in Gujarat:

    • This PM ETS was launched in Surat, Gujarat in 2019.
    • It is the world’s first pilot project targeting particulate pollution using a market-based emissions trading system.
    • It is India’s first emissions trading initiative for any pollutant.
    • The scheme aims to reduce emissions from industries using solid (coal, lignite) and liquid fuels (diesel) by controlling fine particulate matter (PM).
    • How It Works?
      • Cap-and-Trade: Regulators set a cap on total emissions, and industries are issued permits (1 kg of particulate matter per permit).
      • Permit Allocation: 80% of permits are given for free; 20% are sold via auctions.
      • Market Trading: Permits can be bought or sold to meet emission targets. A ceiling price (Rs 100/kg) and floor price (Rs 5/kg) are set.
      • Compliance: Non-compliant industries face fines double the ceiling price for each excess emission.

    Successes of PM-ETS:

    • Reduction in Emissions: Participating plants cut emissions by 20-30% compared to traditional methods.
    • Improved Compliance: 99% compliance in participating plants.
    • Cost-Effective: The system allowed industries to choose the most cost-effective methods for compliance.

    Limitations of PM-ETS:

    • Over-reliance on Free Permits: Smaller plants may struggle as the number of free permits decreases.
    • Supply Chain Limitations: Tightened caps could increase costs for industries not reducing emissions.
    • Market Manipulation: Concerns over unfair permit trading.
    • Geographical Constraints: Limited to Surat, restricting broader impact.
    [UPSC 2011] Regarding “carbon credits’’, which one of the following statements is not correct?

    (a) The carbon credit system was ratified in conjunction with the Kyoto protocol.

    (b) Carbon credits are awarded to countries or groups that have reduced greenhouse gases below their emission quota.

    (c) The goal of the carbon credit system is to limit the increase of carbon dioxide emission.

    (d) Carbon credits are traded at a price fixed from time to time by the United Nations environment programs. *

     

  • What is Flue Gas Desulphurisation (FGD)?

    Why in the News?

    The Union Environment Ministry’s 2015 policy mandating the installation of Flue Gas Desulphurisation (FGD) equipment in all of India’s 537 coal-fired plants has been scrutinised by a recent study commissioned by the Office of the Principal Scientific Adviser.

    Flue Gas Desulphurisation (FGD)

    About Flue Gas Desulphurisation (FGD) in Power Plants

    • FGD is used to remove sulfur dioxide (SO₂) from flue gases in coal-fired power plants.
    • The process involves passing exhaust gases through a scrubbing system using absorbents like ammonia, sodium sulfite, or limestone.
    • Methods:
      • Wet Limestone Scrubbing: Gases pass through a scrubber tower with a slurry of water and limestone.
      • Dry Sorbent Injection: Uses a dry alkaline agent to neutralize SO₂.
      • Sea Water-Based Systems: Utilizes seawater’s natural alkalinity to absorb SO₂.
    • FGD can remove up to 95% of sulfur dioxide, reducing SO₂ emissions significantly.
    • Reduces sulfur emissions, major contributors to acid rain and air pollution.
    • FGD Gypsum, a byproduct, can be used in industries like cement manufacturing.

    Recent Study on FGD in Power Plants

    • A study by NIAS critiques India’s FGD policy, recommending limited FGD installations for plants using imported or high-sulfur coal.
    • 92% of coal in Indian plants has low sulfur content (0.3%-0.5%), meaning FGD may not significantly improve local air quality.
    • Widespread FGD installation could increase power and water consumption, and result in 69 million tonnes of additional CO₂ emissions by 2030.
    • Removing SO₂ (cooling agent) while increasing CO₂ emissions may accelerate climate change.
    • Recommendations: Installing electrostatic precipitators (₹25 lakh per MW) can reduce 99% of particulate matter (PM), offering a more cost-effective and impactful solution.
    [UPSC 2024] According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions?

    (a) Locomotives using fossil fuels

    (b) Ships using fossil fuels

    (c) Extraction of metals from ores

    (d) Power plants using fossil fuels*

     

  • New frog species ‘Leptobrachium aryatium’ discovered in Assam

    Why in the News?

    A 21-year-long study has resulted in the discovery of a new frog species, Leptobrachium aryatium, named after Arya Vidyapeeth College in Assam.

    About the frog ‘Leptobrachium aryatium’

    • Leptobrachium aryatium, a newly discovered species of frog, was found in the Garbhanga Reserve Forest, located on the southwestern edge of Guwahati, Assam, near the Meghalaya border.
    • The species was identified through a re-analysis of past research and new studies on the Leptobrachium genus.
    • Key Features:
      • Distinctive Eyes: The frog has fiery orange-and-black eyes, setting it apart from other species in the genus.
      • Reticulated Throat Pattern: A unique reticulated pattern on its throat adds to its distinct appearance.
      • Smooth, Rhythmic Call: Emits a smooth, rhythmic call at dusk, a feature unique to this species in the genus.
      • Molecular and Morphological Distinctiveness: DNA analysis and physical studies confirmed it as a new species, distinguished by its unique call and appearance.
    [UPSC 2016] Recently, our scientists have discovered a new and distinct species of banana plant which attains a height of about 11 metres and has orange-coloured fruit pulp. In which part of India has it been discovered?

    (a) Andaman Islands* (b) Anaimalai Forests (c) Maikala Hills (d) Tropical rain forests of northeast

     

  • Delamination of the Indian Plate

    Why in the News?

    Recent studies reveal that the Indian Plate is splitting into two, with the lower part detaching and sinking into the Earth’s mantle, a process called delamination, as published by the American Geophysical Union.

    About Delamination:

    • Delamination in tectonic plates refers to the process where the lower part of a continental plate, including the lower crust and/or lithospheric mantle, splits and sinks into the Asthenosphere.
    • This process is driven by density differences and can lead to rapid uplift, changes in stress regimes, and altered magmatism.
    • It can occur in various tectonic settings, including compressional zones, subduction zones, and intraplate regions. 
    • The denser lower part of the plate, including the lower crust and/or lithospheric mantle, is less buoyant than the less dense asthenosphere, leading to sinking.
    • High temperatures can also weaken the lithosphere and facilitate delamination.

    Delamination of the Indian Plate

    Indian Plate and Its Splitting:

    • The Indian Plate has been colliding with the Eurasian Plate for about 60 million years, causing the formation of the Himalayas and influencing regional seismic activity.
    • It is shifting northward at a rate of approximately 5 cm per year..
    • The lower, denser part of the Indian Plate is detaching and sinking into the Earth’s mantle.
    • This may lead to increased seismic activity due to shifts in tectonic stress.
    • In regions like the Himalayan collision zone, delamination results in fractures that increase stress in the Earth’s crust, raising the likelihood of seismic events.
    [UPSC 2004] Consider the following geological phenomena:

    1. Development of a fault 2. Movement along a fault 3. Impact produced by a volcanic eruption 4. Folding of rocks Which of the above cause earthquakes?

    Options:

    (a) 1, 2 and 3 (b) 2 and 4 (c) 1, 3 and 4 (d) 1, 2, 3 and 4

     

  • How govern-mentality exacerbates the problem of farmers’ stubble burning

    Why in the News?

    A new study by researchers Sujit Raghunathrao Jagadale and Javed M. Shaikh from IIM Amritsar looks at the issue of stubble burning by examining how government policies and market systems are failing to manage the problem effectively.

    Why do farmers continue stubble burning despite its harm to air quality?

    • Cost-Effective Method: Stubble burning is the cheapest way for farmers to clear their fields after harvesting. Eg: Farmers burn stubble to quickly prepare their land for the next crop, especially for wheat, without incurring high labor or machinery costs.
    • Lack of Affordable Alternatives: There are limited affordable and efficient alternatives to stubble burning. Eg: Farmers often do not have access to technology or subsidies for machines that can manage stubble, such as Happy Seeder or bio-decomposers.
    • Government’s Focus on High-Yield Crops: The Minimum Support Price (MSP) policy incentivizes the cultivation of wheat and rice, leading to monocropping. Eg: Farmers are encouraged to grow rice continuously, which results in an abundance of stubble that needs to be disposed of quickly.
    • Debt and Economic Pressure: Many farmers face financial pressures, including debt and low returns on their crops, which makes burning stubble a way to save time and money. Eg: Farmers often sell their crops to middlemen at low prices, leaving them with insufficient income to invest in sustainable farming practices.
    • Lack of Strong Enforcement or Support: Although stubble burning is penalized, enforcement of laws is weak, and farmers often feel the state does not provide adequate support for eco-friendly methods. Eg: Despite penalties, farmers feel little pressure to change practices when there is insufficient governmental support or infrastructure for alternatives.

    How does India’s MSP policy influence stubble burning?

    • Encourages Monocropping: The MSP policy promotes the cultivation of high-yield crops like rice and wheat, leading to monocropping, which results in a large amount of stubble that must be cleared. Eg: Farmers in Punjab often grow rice followed by wheat, creating a cycle where large quantities of rice stubble need to be burned to prepare the soil for the next crop.
    • Limits Crop Diversification: The MSP system prioritizes wheat and rice over other crops, making it economically unfeasible for farmers to switch to more sustainable practices or crops that would reduce stubble burning. Eg: Despite the potential for growing other crops, farmers focus on rice and wheat to benefit from MSP, leaving them with stubble that they have no economically viable option to manage.
    • Financial Constraints: The MSP rates for crops like rice and wheat have remained stagnant, making it harder for farmers to invest in alternatives to stubble burning, such as machinery or composting. Eg: With wheat MSP seeing only minimal increases, farmers struggle to cover costs for labor and inputs, leading them to resort to stubble burning as the most cost-effective option to clear fields.

    What has the government done in this situation?

    • Implemented Subsidies for Machinery: The government has provided subsidies for the purchase of machinery like the Happy Seeder to help farmers manage stubble without burning. Eg: The Punjab government has distributed equipment like straw management machines under the Sub-Mission on Agricultural Mechanization to reduce stubble burning.
    • Awareness Campaigns: The government has conducted awareness programs to educate farmers about the harmful effects of stubble burning and encourage them to adopt alternative practices. Eg: The Ministry of Agriculture and local bodies in states like Punjab and Haryana have launched campaigns to raise awareness about the environmental and health risks of stubble burning.
    • Legal Measures and Penalties: Various state governments, including Punjab, have imposed fines and penalties on farmers found burning stubble, aiming to deter the practice. Eg: The Punjab government introduced a fine for stubble burning, with penalties reaching up to Rs 2,500 for each violation, although enforcement remains challenging.

    Way forward: 

    • Promote Crop Diversification: Encourage farmers to shift from paddy to less water-intensive and non-stubble-generating crops through assured procurement and better MSP for alternative crops. Eg: Incentivize crops like millets and pulses to reduce stubble generation.
    • Strengthen Support and Infrastructure: Scale up access to sustainable stubble management technologies and ensure timely financial and logistic support to small and marginal farmers. Eg: Expand reach of Happy Seeder and bio-decomposer solutions through local cooperatives and custom hiring centers.

    Mains PYQ:

     [UPSC 2015] Mumbai, Delhi and Kolkata are the three Mega cities of the country but the air pollution is much more serious probelm in Delhi as compared to the other two. Why is this so?

    Linkage: Delhi’s severe air pollution, especially at certain times of the year, is caused by a combination of its location in the Indo-Gangetic Plain, nearby states burning crop stubble, and weather conditions that trap pollutants.

  • Study finds a Shift in Peak Time of Maximum Rainfall

    Why in the News?

    A recent study published in Geophysical Research Letters revealed changes in the amount and timing of rainfall using GSMaP Data between 2001-2010 and 2011-2020.

    About Global Satellite Mapping of Precipitation (GSMaP)

    • GSMaP is a specialized precipitation product developed through collaboration between ISRO (Indian Space Research Organisation) and JAXA (Japan Aerospace Exploration Agency).
    • It provides high-resolution precipitation data with a 0.1° x 0.1° grid and one-hour temporal resolution, focusing on the Indian subcontinent since March 2000.
    • The data supports rainfall trend analysis, climate modelling, and water resource management.

    Study finds a Shift in Peak Time of Maximum Rainfall

    Key Findings of the Study:

    • Rainfall Trends:
      • West-Central India: Increased daily rainfall (2 mm/day) from 2011-2020 compared to 2001-2010.
      • Eastern India: A decrease of ~1 mm/day in rainfall during the same period.
      • Regional Shifts: Northeastern and eastern India saw decreased rainfall, while the Indo-Gangetic Plain and southern India experienced increases.
    • Vegetation & Soil Moisture:
      • West-Central India saw an increase in vegetation (NDVI from 0.2 to 0.4) and soil moisture linked to increased rainfall.
      • Eastern India had decreased soil moisture during the same period.
    • Shifts in Peak Rainfall Timing:
      • Indo-Gangetic Plain: Peak rainfall advanced by 2-4 hours.
      • West-Central India: Peak rainfall delayed by 1-2 hours.
    • Factors responsible for this Shift:
      • Higher soil moisture supports rainfall, while reduced moisture, particularly in eastern India, decreases rainfall.
      • Higher aerosol concentrations in polluted areas like the Indo-Gangetic Plain lead to earlier rainfall peaks.
      • Changes in atmospheric circulation, topography, and coastal influences also affect rainfall distribution and timing.
    [UPSC 2012] Consider the following statements:

    1. The duration of the monsoon decreases from southern India to northern India.

    2. The amount of annual rainfall in the northern plains of India decreases from east to west.

    Which of the statements given above is / are correct?

    (a) 1 Only (b) 2 Only (c) Both 1 and 2 (d) Neither 1 nor 2

     

  • What is Atmospheric River?

    Why in the News?

    Earlier this month, severe weather in the United States, including heavy rainfall, strong winds, and thunderstorms, was caused by an Atmospheric River.

    What is an Atmospheric River?

    • An atmospheric river is a narrow, fast-moving band of moisture and wind that transports large amounts of water vapor across vast distances.
    • They form when large-scale weather patterns align, creating channels of moisture transport from tropical oceans, guided by low-level jet streams toward the coast.
    • They typically span 402-606 km in width and can extend over 1600 km in length.
    • The most powerful atmospheric rivers transport moisture equivalent to the Mississippi River’s flow.
    • Example: The Pineapple Express, a well-known atmospheric river, transports moisture from Hawaii to the West Coasts of the U.S. and Canada.
    • The intense rainfall from atmospheric rivers leads to flooding, mudslides, and infrastructure damage, with wind speeds comparable to hurricanes.

    Impact and Climate Change:

    • Rising global temperatures cause more water to evaporate, and warmer air can hold more moisture.
    • For every 1°C increase, the atmosphere can hold 7% more moisture, leading to stronger storms.
    • Research indicates such events will likely grow longer and more intense.
    [UPSC 2023] With reference to the Earth’s atmosphere, which one of the following statements is correct?

    (a) The total amount of insolation received at the equator is roughly about 10 times of that received at the poles.

    (b) Infrared waves are largely absorbed by carbon dioxide that is concentrated in the upper atmosphere.

    (c) Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.  

    (d) Ultraviolet rays are absorbed by the ozone layer lying in the ionosphere.