Contemporary Environmental Issues — UPSC Environment Notes

1. The 'Evil Quartet' of Biodiversity Loss

Jared Diamond coined this term to describe the four major anthropogenic (human-caused) drivers of extinction.

Habitat Loss and Fragmentation: This is the primary cause of extinction. Large habitats are broken into small fragments due to human activities (agriculture, urban sprawl), making them unable to support species. *Example:18% of the Amazon rainforest has been completely lost as of 2022.

Over-Exploitation: When 'need' turns to 'greed', species are harvested faster than they can recover. *Example:The Steller’s Sea Cow and Passenger Pigeon were hunted to extinction by humans.

Alien Species Invasion: Introducing non-native species (intentionally or accidentally) can decimate indigenous populations. *Example:The Nile Perch introduced into Lake Victoria led to the extinction of over 200 species of cichlid fish.

Co-extinctions: When a host species goes extinct, all obligate species (those that depend strictly on the host) also perish. *Example:If a specific host fish goes extinct, its unique parasites also vanish forever.

2. Climate Change: The Modern Extinction Driver

Beyond the original quartet, climate change is now driving mass mortality and ecosystem shifts.

Ecological Shifts: Changing temperatures alter breeding cycles and migratory patterns, leading to a mismatch between species and their food sources.

Disease & Mortality: Warming climates facilitate the spread of pathogens into new areas.

Historical Landmark: The Bramble Cay melomys (a rodent) is the first mammal officially reported to have gone extinct due to anthropogenic climate change (sea-level rise and storm surges).

1. Pollution and Species Decline

Pollution serves as a silent driver of extinction, often altering habitats in ways that are not immediately visible.

The Urban Example: The decline of the House Sparrow in India is a classic case of dual pressure:

- Invisible Pollution: Electromagnetic radiation from mobile towers affecting their biological systems.

- Habitat Loss: Modern urban building designs eliminate traditional nesting cavities.

2. Ecosystem Stability and Services

Biodiversity acts as a buffer against environmental volatility. When species are lost, the entire 'web of life' weakens.

Reduced Functioning: Ecosystems become less resilient to climate shocks, leading to failures in services like water purification, pollination, and soil fertility.

Accelerated Extinction: Human activities (anthropogenic factors) have pushed the current extinction rate to 1,000–10,000 times the natural background rate.

3. Zoonotic Spillover and Human Health

One of the most dangerous impacts of biodiversity loss is the increased proximity between humans and pathogens.

The Spillover Effect: When land is cleared for agriculture or pasture, the 'zoonotic spillover' process—where diseases jump from animals to humans—accelerates.

Pandemic Risk: Approximately 60-75% of human infectious diseases are zoonotic in origin.

Transportation Links: Encroachment into remote forests creates transit paths that allow diseases to travel from rural wilderness to densely populated cities in days.

4. Socio-Economic Impacts

Human-Wildlife Conflict: As natural habitats shrink, animals venture into human settlements, leading to crop damage, livestock loss, and physical injuries to both humans and wildlife.

Food and Medicine: Sustainable agriculture depends on diverse genetic pools. Furthermore, current loss rates threaten both traditional medicine and modern pharmaceutical drug innovation derived from rare plant/animal compounds.

1. The Greenhouse Effect

The atmosphere's ability to trap heat is essential for life, but the current anthropogenic (human-caused) surge in gas levels is disrupting the Earth's energy balance.

2. Primary Greenhouse Gases

Water Vapor: The most abundant GHG. Unlike others, it has a very short residence time (a few days) and acts as a feedback loop rather than a direct driver of long-term warming.

Carbon Dioxide (CO2): The most significant anthropogenic GHG. Human activities have increased atmospheric CO2 by 50% in less than 200 years. - *Sources:Fossil fuel combustion, deforestation, and volcanic eruptions.

Methane (CH4): The second most abundant human-caused GHG. It is significantly more potent than CO2 at trapping heat over a 100-year period. - *Sources:Agriculture (livestock), rice paddies, wetlands, and landfills.

Nitrous Oxide (N2O): A potent gas where natural sources (soil/ocean bacteria) still contribute a majority (62%) of total emissions. - *Sources:Fertilizers in agriculture and industrial combustion.

Fluorinated Gases (F-Gases): These are entirely synthetic (man-made) and do not occur in nature. They include HFCs, PFCs, and SF6. - *Feature:Even in tiny concentrations, they trap heat thousands of times more effectively than CO2.

1. How the Natural Greenhouse Effect Works

The natural greenhouse effect is essential for maintaining Earth's average temperature at a life-sustaining 15°C. Without it, the planet would be a frozen -18°C.

Incoming Sunlight: The sun emits shortwave radiation (visible light) that passes through the atmosphere easily.

Surface Heating: This radiation is absorbed by the Earth’s surface (land and oceans), warming the planet.

Outgoing Heat: The warmed Earth then radiates energy back toward space as longwave radiation (infrared light).

Heat Trapping: Greenhouse gases (GHGs) in the atmosphere absorb some of this infrared light and radiate it back toward the surface, keeping the planet warm.

2. The Enhanced Greenhouse Effect

This refers to the additional radiative forcing caused by human-induced (anthropogenic) increases in GHG concentrations.

The Problem: Activities like burning fossil fuels, deforestation, and industrial farming have added a 'thick blanket' of gases to the atmosphere.

The Result: More heat is trapped than is necessary, causing the global average temperature to rise—a phenomenon known as Global Warming.

Key Drivers: The primary gases causing this enhancement are:

Carbon Dioxide (CO2): From burning coal, oil, and gas.

Methane (CH4): From livestock and landfills.

Nitrous Oxide (N2O): From fertilizers.

Synthetic Gases: Such as HFCs and HCFCs from refrigeration.

Tropospheric Ozone: Formed from pollutants in the lower atmosphere.

1. What is Global Warming?

Global warming refers to the long-term heating of Earth's climate system observed since the pre-industrial period (1850-1900).

Primary Cause: Human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere.

Difference from Climate Change: While global warming refers specifically to temperature rise, Climate Change is a broader term encompassing warming and its side effects (like melting glaciers and heavier rainstorms).

2. Global Warming Potential (GWP)

GWP allows for a direct comparison of the global warming impacts of different gases. It essentially tells us how much 'stronger' or 'weaker' a gas is compared to CO2.

The Reference Gas: CO2 is the baseline with a GWP of 1.

Calculation: It measures the energy absorbed by 1 ton of a gas over a time period (usually 100 years) relative to 1 ton of CO2.

Potency vs. Concentration: Some gases (like SF6) are present in tiny amounts but are thousands of times more effective at trapping heat than CO2.

3. Atmospheric Lifetime

This refers to the average time a gas molecule stays in the atmosphere before being removed by chemical reactions or being absorbed by 'sinks' (like the ocean or forests).

Short-lived: Methane stays for only about 12 years but is very potent during that time.

Long-lived: PFCs can stay in the atmosphere for up to 50,000 years, meaning their warming effect is essentially permanent on a human timescale.

1. Natural Factors Affecting Climate Change

Earth's climate has always been in flux due to massive natural systems operating over thousands to millions of years.

Milankovitch Cycles: These are three periodic changes in Earth's orbit and tilt that affect solar energy distribution: 1. Eccentricity: The shape of Earth's orbit around the Sun. 2. Axial Tilt (Obliquity): The angle Earth's axis is tilted relative to its orbital plane. 3. Precession: The 'wobble' of Earth's axis. Solar Radiation: Variations in the Sun's energy output directly impact atmospheric and oceanic temperatures. Volcanic Activity: While volcanoes release CO2, large eruptions can also release aerosols that temporarily cool the Earth by reflecting sunlight. Plate Tectonics & Ocean Currents: The movement of continents alters the flow of ocean currents, which are the planet's primary 'conveyor belts' for heat and moisture. ENSO (El Niño-Southern Oscillation): A periodic shift in ocean temperatures in the tropical Pacific that disrupts global weather patterns.

2. Anthropogenic (Man-made) Factors

Since the Industrial Revolution, human activities have become the primary driver of climate change through the Enhanced Greenhouse Effect.

Burning Fossil Fuels: Coal, oil, and gas release stored carbon (as CO2) into the atmosphere, which has been buried for millions of years. Deforestation: Forests act as 'Carbon Sinks'. Cutting them down reduces the planet's capacity to absorb CO2 and often releases stored carbon if trees are burned. Agriculture: Livestock (methane from enteric fermentation) and fertilizers (nitrous oxide) are major sources of non-CO2 greenhouse gases. Urbanization: Replacing natural vegetation with concrete and asphalt creates 'Urban Heat Islands' and alters local carbon cycles.

1. What are Atmospheric Aerosols?

Aerosols are a suspension of fine solid particles or liquid droplets in the air. They range from microscopic to large enough to be seen as smoke or dust clouds.

Sources of Aerosols:

Natural Sources: Mineral dust from deserts, sea salt from ocean spray, volcanic ash, and organic compounds released by forests.

Anthropogenic (Human) Sources: Sulfates and nitrates from industrial emissions, and carbon particles from burning fossil fuels or agricultural waste.

2. Impact on Climate: The Dual Role

Aerosols affect the Earth's energy balance in two primary ways:

Direct Effects:

Scattering: Most aerosols (like sulfates) reflect sunlight back into space, which has a cooling effect on the surface.

Absorption: Some aerosols (like Black Carbon) absorb solar energy, warming the atmosphere.

Indirect Effects (Cloud Modulation):

Cloud Nuclei: Aerosols act as seeds (Cloud Condensation Nuclei) for water droplets to form. Higher aerosol concentrations can lead to clouds with more, but smaller, droplets, making clouds brighter and longer-lasting, which usually cools the planet.

3. Black Carbon (Soot)

Black Carbon is a distinct type of aerosol produced by the incomplete combustion of fossil fuels, biofuels, and biomass.

Potency: Per unit of mass, it has a warming impact 460 to 1,500 times stronger than CO2.

Short-lived Pollutant: Unlike CO2 which stays for centuries, Black Carbon remains in the air for only days to weeks. This means reducing emissions can result in immediate climate benefits.

Impact on Ice: When Black Carbon settles on snow or glaciers, it darkens the surface, reducing albedo (reflectivity). The surface absorbs more heat, causing rapid melting of Himalayan or Arctic ice.

1. Impact on Weather Patterns

Rising global temperatures act as a catalyst for extreme weather events.

Intense Heatwaves: Rising averages cause more frequent and deadly heatwaves. In India, heatwaves are a leading cause of weather-related mortality (e.g., 2018 heatwave affecting 20 states).

Stronger Storms: Warmer air holds more moisture, providing more 'fuel' for tropical cyclones. This leads to storms that are wetter, more intense, and capable of rapid intensification.

2. Environmental Consequences

Climate change triggers a chain reaction across the planet's cryosphere and oceans.

Cryosphere Collapse: Glaciers in Greenland, Antarctica, and the Himalayas are melting at unprecedented rates.

Sea-level Rise: Melting ice and thermal expansion of water are raising sea levels. This threatens to make nations like the Maldives (80% uninhabitable by 2050) vanish.

Ocean Acidification: As oceans absorb more CO2, their pH levels drop. This process is accelerated in the Arctic due to melting ice.

Inland Shifts: Increased droughts due to heat, and increased flooding due to erratic heavy rain and snowmelt.

Ecosystem Resilience: Hotter, drier climates lead to severe wildfire seasons (e.g., Australia and California) and disrupt natural pest-control cycles.

3. Impact on Animals & Marine Life

Species that cannot adapt to rapid habitat shifts face local or total extinction.

Ice-Dependent Species: Walruses, polar bears, and penguins lose critical hunting and breeding grounds as ice sheets shrink.

Coral Bleaching: Rising sea temperatures cause corals to expel their symbiotic algae, leading to 'bleaching' and the collapse of entire marine biodiversity hubs.

Inundation: Sea-level rise destroys coastal nesting grounds for birds and marine invertebrates.

The First Casualty: The Bramble Cay melomys (a rodent) is the first mammal officially recorded to have gone extinct due to anthropogenic climate change.

1. Impact on Human Health

Climate change acts as a direct and indirect threat to physiological and psychological well-being.

Air Quality & Respiratory Health: Increased temperatures lead to higher concentrations of ground-level ozone (smog) and wildfire smoke, worsening asthma and heart disease.

Vector-Borne Diseases: Warmer climates expand the geographical range of insects, spreading diseases like Malaria, Zika, and Dengue to new regions.

Mortality Projections: WHO estimates that between 2030 and 2050, climate change will cause 250,000 extra deaths per year from heat stress, diarrhea, and malnutrition.

Mental Health: Eco-anxiety is rising; nearly 45% of youth globally report that climate concerns interfere with their daily functioning.

2. Impact on Economy

The economic backbone, particularly in developing nations, is highly vulnerable to climatic shifts.

Agricultural Disruption:

Soil Quality: Extreme heat and erratic rain leach nutrients and cause soil erosion.

Pest Outbreaks: Warmer winters allow pests and invasive species to survive and devastate crops.

Livestock Stress: High temperatures reduce milk yield and increase mortality in cattle.

Food Security: Supply chain shocks from hurricanes and droughts lead to global food shortages and price inflation, hitting the poor the hardest.

Sectoral Collapse: Industries like fishing (due to warming oceans) and tourism (due to lost biodiversity/beaches) face potential collapse.

3. Impact on Society

Climate change is not an 'equalizer'; it widens the gap between the haves and the have-nots.

Increased Inequality: Developing nations, despite contributing least to emissions, suffer the most as they lack the financial 'buffer' or infrastructure to adapt.

Environmental Refugees: In 2021 alone, 23.7 million people were displaced by floods and cyclones. Sea-level rise and water scarcity are creating a new class of 'climate migrants'.

Resource Conflicts: Scarcity of water and fertile land increases the likelihood of civil unrest and cross-border tensions.

1. What is Ozone (O3)?

Ozone is an inorganic molecule composed of three oxygen atoms. Its name is derived from the Greek word *ozein*, meaning 'to smell', due to its distinctively pungent odor.

2. The Ozone-Oxygen Cycle (Photolysis)

Ozone is constantly created and destroyed through a natural process powered by sunlight:

Formation: High-energy UV-C rays strike an oxygen molecule (O2) and split it into two free oxygen atoms (atomic oxygen). These free atoms then combine with other O2 molecules to form Ozone (O3) .

Natural Destruction: Ozone is also naturally broken down by sunlight and reactions with trace amounts of nitrogen, hydrogen, and chlorine, maintaining a steady-state balance in an unpolluted atmosphere.

Significance of the Cycle:

Radiation Shield: The continuous absorption of high-energy UV radiation prevents harmful rays from reaching the Earth's surface.

Stratospheric Heating: The chemical reactions involved in this cycle release heat, which is responsible for the temperature increase with altitude in the stratosphere.

3. The Ozonosphere

The ozone layer is a region of high ozone concentration situated between 15–30 km above the Earth's surface.

Altitude: While it spans the stratosphere, the concentration is highest between 19 and 23 km .

Global Movement: Most ozone is created over the Equator (where solar intensity is highest) but is transported by stratospheric winds toward the poles.

Distribution: Consequently, under normal conditions, the highest ozone levels are found over the Arctic and Siberia , while the lowest are found near the Equator.

1. Good Ozone: The Stratospheric Shield

Approximately 90% of the Earth's ozone is located in the stratosphere (15–30 km above the surface).

Role: It functions as Earth's sunscreen, absorbing the majority of the sun's high-energy ultraviolet (UV) radiation.

Impact: Without this protective layer, increased UV radiation would lead to higher rates of skin cancer, cataracts, and damage to terrestrial and aquatic ecosystems.

2. Bad Ozone: The Tropospheric Pollutant

The remaining 10% of ozone is found in the troposphere, the layer of the atmosphere closest to the ground.

Nature: It is a secondary pollutant, meaning it is not emitted directly from tailpipes or chimneys but forms through chemical reactions in the presence of sunlight.

Formation (Photochemical Smog): It is created when Oxides of Nitrogen (NOx) and Volatile Organic Compounds (VOCs) react in the air.

Impact: It is a primary component of smog. Breathing ground-level ozone can trigger chest pain, coughing, throat irritation, and worsen bronchitis, emphysema, and asthma.

3. Comparison of Chemical Dynamics

While the chemical formula (O3) remains the same, the context of its existence changes its environmental value:

Stratosphere: Naturally occurring and protective.

Troposphere: Human-induced (mostly) and hazardous.

1. The Science of Depletion

Ozone depletion is the thinning of the ozone layer caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities.

Historical Timeline:

1974: Scientists Rowland and Molina warned that human-generated CFCs were attacking the ozone layer.

1985: The British Antarctic Survey discovered the recurring springtime 'Ozone Hole' over Antarctica, proving the theory true.

1994: The Nobel Prize in Chemistry was awarded to Rowland, Molina, and Paul Crutzen for their work on ozone chemistry.

2. Ozone Depleting Substances (ODS)

These are synthetic gases, often called halocarbons, which are stable in the lower atmosphere but break down in the stratosphere, releasing atoms that destroy ozone molecules.

CFCs (Chlorofluorocarbons): The primary culprit; used in refrigeration, ACs, and as solvents.

HCFCs: Transitional substitutes for CFCs, but they still possess ozone-depleting potential.

Halons: Exceptionally potent; containing bromine, these are used primarily in fire extinguishers.

Carbon Tetrachloride: Used in industrial degreasing and as a precursor to CFCs.

Methyl Bromide: A powerful fumigant used in agriculture to control pests in soil and crops.

Methyl Chloroform: Widely used as an industrial solvent and cleaner.

1. Mechanism of Ozone Destruction

The destruction of ozone is a catalytic process, meaning a single chlorine or bromine atom can destroy thousands of ozone molecules without being consumed.

1. Transport: Ozone-depleting substances (ODS) reach the stratosphere.

2. Breakdown: High-energy solar UV radiation breaks these chemicals apart.

3. Release: Highly reactive Chlorine and Bromine atoms are released.

4. Catalytic Reaction: These atoms react with ozone ($O_3$), breaking it into oxygen ($O_2$) and starting a chain reaction.

2. The Antarctic Ozone Hole

The 'hole' is not a physical void but a region of extreme depletion (< 220 Dobson Units) occurring annually between August and October.

Why Antarctica?

Meteorological Conditions: Extreme cold, stable high-pressure systems, and high wind speeds create a unique environment.

Polar Stratospheric Clouds (PSCs): In the extreme cold, PSCs form; these clouds provide a surface for chemical reactions that convert 'reservoir' chlorine into 'active' ozone-destroying chlorine.

3. Impacts of UV-B Radiation

Thinning of the ozone layer acts as a gatekeeper, letting in harmful UV-B rays.

Human Health: Causes DNA damage leading to skin cancers (melanoma), cataracts (eye damage), premature skin aging, and a weakened immune system.

Agriculture & Forestry: UV-B hinders photosynthesis and development in sensitive crops like rice, wheat, and soybean. Commercially important timber trees also suffer growth stunting.

Marine Life: Threatens Phytoplankton, which form the base of the marine food web. It also damages the larval stages of fish, shrimp, and crabs.

Materials: Accelerates the degradation of synthetic polymers, plastics, and wood used in outdoor construction.

4. The Ozone Depleting Gas Index (ODGI)

Origin: Developed by NOAA in the 1990s.

Function: It tracks the concentration of chlorine and bromine in the stratosphere relative to its peak in the 1990s.

Current Trend: The 2022 ODGI shows a significant reduction in ODS, proving the success of global phase-out efforts.

1. Vienna Convention (1985)

The Vienna Convention for the Protection of the Ozone Layer served as the framework for international efforts to protect the ozone layer.

Nature: It is a non-binding framework convention. It does not require countries to take specific actions to control ozone-depleting substances (ODS).

Focus: It emphasizes international cooperation in research, monitoring, and information exchange.

Significance: It paved the way for the legally binding Montreal Protocol.

2. Montreal Protocol (1987)

The Montreal Protocol is a landmark agreement that regulates the production and consumption of nearly 100 man-made ODS.

Binding Commitments: Unlike the Vienna Convention, it sets legally binding goals and time-targeted schedules for phasing out ODS.

Common But Differentiated Responsibilities (CBDR): While all 198 parties have commitments, developed and developing countries have different phase-out timetables based on their capacities.

Financial Support: The Multilateral Fund (MLF) helps developing countries cover the 'incremental costs' of switching to ozone-friendly technologies.

3. Key Amendments to the Protocol

The Protocol is a 'living treaty' that has been strengthened over time:

London (1990): Created the Multilateral Fund and added Methyl Chloroform to the control list.

Copenhagen (1992): Accelerated phase-outs and included HCFCs (for developed countries).

Kigali (2016): A major shift—it targets HFCs (Hydrofluorocarbons). While HFCs do not deplete ozone, they are potent greenhouse gases. This links ozone protection with climate change mitigation.

1. The Problem

Scale: CPCB estimated India's plastic waste generation at about 3.4 million tonnes in 2019-20; a large share is packaging used once.

Why it persists: Conventional plastics are petroleum-based polymers that do not biodegrade; they fragment into microplastics (less than 5 mm) that enter soil, rivers, oceans and the food chain.

Collection gap: Much plastic is collected by the informal sector (waste pickers); low-value multilayered packaging (chips packets, sachets) is rarely recycled and is often burnt or dumped.

Impacts: Clogged drains worsen urban floods, open burning releases dioxins and furans, ingestion harms cattle and marine life.

2. Legal Framework

Parent law: PWM Rules are notified under the Environment (Protection) Act, 1986.

PWM Rules, 2016: Responsibilities for local bodies, gram panchayats, waste generators, producers, importers and brand owners; introduced EPR.

2021 amendment: Banned identified single-use plastic (SUP) items with low utility and high littering potential from 1 July 2022 (e.g. earbuds with plastic sticks, plastic flags, cutlery, straws, stirrers, thin wrapping films); carry-bag thickness raised to 75 micron (Sept 2021) and 120 micron (Dec 2022).

EPR Guidelines, 2022: Mandatory targets for collection and recycling of plastic packaging, minimum recycled content and an online centralised EPR portal run by CPCB with tradable EPR certificates.

2024 amendment: Tightened definitions and labelling for biodegradable and compostable plastics and strengthened producer reporting.

3. Institutions

CPCB / SPCBs: Monitor compliance, register producers and recyclers.

Urban Local Bodies: Segregation at source and collection under the Solid Waste Management Rules, 2016 and Swachh Bharat Mission (Urban) 2.0.

4. Global Action

UNEA-5.2 (Nairobi, March 2022): Resolution to negotiate a legally binding instrument on plastic pollution covering its full life cycle.

Negotiations: Rounds at Busan (2024) and Geneva (2025) ended without final agreement; disagreement centres on capping primary plastic production versus focusing on waste management.

India's position: Supports action on waste and circularity, cautious about production caps and trade restrictions.

5. Way Forward

Circular economy: Design for recyclability, deposit-return schemes, uniform labelling.

Integrate waste pickers into formal collection with ID cards and social security.

Alternatives: Promote reusable systems and genuinely compostable materials with testing standards.

1. Major Pollutants

Particulate matter: PM10 and PM2.5 (diameter ≤2.5 micrometre) penetrate deep into lungs and the bloodstream; PM2.5 is the most harmful for health.

Gases: Sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ground-level ozone (O3, a secondary pollutant formed from NOx and VOCs in sunlight), ammonia (NH3).

2. Sources

Transport: Vehicle exhaust and road dust, especially in cities.

Industry and power: Coal-based thermal plants, brick kilns, small units using dirty fuels.

Construction and demolition dust.

Biomass burning: Crop-residue (stubble) burning in Punjab-Haryana after the kharif harvest; household solid fuels in rural kitchens.

Meteorology: In north India's winter, low wind speed and temperature inversion trap pollutants near the ground; the Indo-Gangetic plain acts like a closed basin.

3. Legal and Institutional Framework

Air Act, 1981: Enacted after the 1972 Stockholm Conference; CPCB and SPCBs enforce it.

NAAQS (2009): Standards for 12 pollutants; PM2.5 annual limit 40 µg/m³, much laxer than the WHO 2021 guideline of 5 µg/m³.

National AQI (2014): Single number and colour band from 8 pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, Pb) with six categories from Good to Severe.

NCAP (January 2019): First national time-bound programme; covers about 130 non-attainment cities; target revised to up to 40% reduction in PM10 by 2025-26 over 2017-18 levels; funds are linked to performance and tracked on the PRANA portal.

CAQM Act, 2021: Statutory commission for Delhi-NCR and adjoining areas, replacing EPCA; enforces GRAP, a stage-wise set of curbs as AQI worsens.

Other measures: BS-VI fuel norms nationwide from April 2020 (skipping BS-V), PM Ujjwala Yojana for LPG, FGD norms for thermal plants, in-situ residue management machines.

4. Way Forward

Airshed approach: Pollution crosses city and state boundaries, so regional planning is needed.

Sector targets: Electric mobility and public transport, cleaner industrial fuels, dust control, viable markets for crop residue.

Health framing: Treat air quality as a public-health emergency with monitoring in smaller towns and rural areas.

1. IMD Criteria for a Heatwave

Basic condition: Maximum temperature of at least 40°C in the plains, 37°C in coastal areas and 30°C in hilly regions.

Departure from normal: Heatwave when the maximum is 4.5°C to 6.4°C above normal; severe heatwave when it is more than 6.4°C above normal.

Actual temperature: Heatwave when the maximum reaches 45°C; severe heatwave at 47°C or more.

2. Causes and Trends

Season: Mainly March–June over north-west, central and east India and parts of Andhra Pradesh–Telangana.

Drivers: Clear skies, dry hot winds (loo), delayed monsoon onset, and El Niño years.

Climate change is increasing the frequency, intensity and duration of heatwaves and warm nights.

Urban Heat Island: Concrete, asphalt, fewer trees and waste heat from vehicles and ACs make cities hotter than surrounding areas, especially at night.

Humid heat: High humidity stops sweat from evaporating; a wet-bulb temperature of about 35°C is regarded as the upper limit of human survival for prolonged exposure.

3. Impacts

Health: Heat exhaustion, heatstroke, worsening of heart and kidney disease.

Economy: Lost working hours in construction and agriculture, lower labour productivity, power demand peaks.

Agriculture: Terminal heat shrivels wheat grains (e.g. March 2022), stresses livestock.

4. Governance Response

Ahmedabad Heat Action Plan (2013): First in South Asia, after the 2010 heatwave; early warnings, cool shelters, drinking water, hospital preparedness, changed work hours.

NDMA guidelines for preparing heat action plans; many states and cities now have plans.

Not a notified disaster: Heatwave is not in the national list of notified disasters for SDRF/NDRF relief; states may use part of SDRF for local disasters they notify.

Cool roofs: Reflective roof coatings (e.g. Telangana Cool Roof Policy) reduce indoor temperatures.

5. Way Forward

Heat-health early warning integrated with hospitals, labour rules for rest breaks and shaded workplaces, urban greening and blue infrastructure, and better mortality reporting.