Complete study notes for BEVAE-181 Block 3 Unit 11. Covers the three major global environmental issues in full detail. Global Warming and Climate Change: the greenhouse effect mechanism, greenhouse gases (CO₂, CH₄, CFCs, water vapour), IPCC findings, temperature rise (0.3–0.6°C since 1860; projected +1.4–5.8°C by 2100), UNFCCC (1992), Kyoto Protocol (1997), Paris Agreement/COP21 (2015), India's NAPCC (2008) and eight National Missions. Ozone Layer Depletion: atmospheric zones, UV-A/B/C types, CFC mechanism, ozone hole discovery (1985), Montreal Protocol (1987), India's phase-outs, and recent healing report (2018). Acid Rain: pH scale, H₂SO₄ and HNO₃ formation, wet and dry deposition, effects on Taj Mahal, crops, water bodies, and buildings. Includes nine diagrams and model answers. Free PDF download.
Unit 11 · Index
Global issues are so named because their impacts damage not only the countries that caused the problems — they go beyond national boundaries and extend to global scale. Solutions require international-level efforts. This unit covers three critical global issues: Global Warming & Climate Change, Ozone Layer Depletion, and Acid Rain — with their causes, effects, and the international conventions and treaties created to address them.
With wide exposure to environment in previous units, we now focus on global issues — topics of hot discussion at various forums in the last few decades. Their causes and effects transcend national boundaries, requiring coordinated international action.
Normal Greenhouse Effect: GHGs absorb infrared radiation emitted by Earth and re-radiate it downward, keeping Earth warm enough for life. Without this, Earth would be -18°C. Enhanced Greenhouse Effect: Human activities increase GHG concentrations → more heat trapped → global warming.
Thermal expansion of ocean water + melting of glaciers and polar ice sheets. Sea level may rise by 0.5 to 1 metre. Threatens coastal populations (India's coastline densely populated).
More vigorous hydrological cycle → more severe floods, rainfall, and droughts. Some areas flood while others become drought-stricken.
Changes in rainfall and soil moisture → food production affected → malnutrition + escalating food prices. India's agriculture = climate-sensitive; NAPCC's National Mission for Sustainable Agriculture.
Warmer climate → increased infections — malaria, dengue, yellow fever, viral encephalitis spreading to new regions.
🇮🇳 India's NAPCC (2008): National Action Plan on Climate Change — 8 National Missions: National Solar Mission · Enhanced Energy Efficiency · Sustainable Habitat · National Water Mission · Sustaining the Himalayan Ecosystem · Green India · Sustainable Agriculture · Strategic Knowledge for Climate Change. All States also directed to prepare State-level Action Plans.
IPCC (Intergovernmental Panel on Climate Change) — established 1988 by WMO and UNEP. Its assessment reports provide scientific basis for climate policy. 1st assessment: 1990. 5th assessment: November 2014.
UNFCCC definition: Climate change = change attributable directly or indirectly to human activity altering the composition of the global atmosphere, in addition to natural climate variability observed over comparable time periods.
IPCC definition: Climate change = change in the state of climate identifiable by changes in mean/variability of properties, persisting for typically decades or longer (can be natural OR anthropogenic).
Gases present in the atmosphere that absorb the infrared radiation (heat) emitted by Earth and do not allow it to fully escape into space are called greenhouse gases. They warm the atmosphere — this is the natural greenhouse effect. Examples: Carbon dioxide (CO₂), Methane (CH₄), Ozone (O₃), Chlorofluorocarbons (CFCs), and Water vapour (H₂O). Water vapour contributes about 2/3 of the greenhouse effect; CO₂ contributes about 1/4.
United Nations Framework Convention on Climate Change. Adopted May 1992. Came into force March 1994. 194 countries + EU have become party. Goal: Stabilise greenhouse gas concentrations at a level preventing dangerous anthropogenic interference with the climate system, within a timeframe allowing ecosystems to adapt, food production to continue, and economic development to proceed sustainably.
Global warming → climate change → altered rainfall patterns and soil moisture. India's agriculture (climate-sensitive) would be seriously affected → crop yield changes → malnutrition and food price escalation. Sea level rise (0.5–1 m) threatens coastal populations — India's densely populated coastline at risk. More intense storms, prolonged droughts, and floods. Spread of diseases like malaria and dengue to new regions. If rate of change too fast → ecosystems and organisms cannot adapt → mass extinctions.
The thinning or depletion of the ozone layer — referred to as "ozone hole." Observed first in Antarctica (1985 — British Antarctic Survey). Data: ~300 DU (1970) → ~200 DU (1984) → ~88 DU (1994). Depletion also confirmed over Arctic and mid-latitude regions (USA, Europe).
| Area Affected | Effect of Increased UV-B |
|---|---|
| Human Health | Cataracts and skin cancer; immune system suppression → increased risk of infectious diseases |
| Terrestrial Plants | Impaired photosynthesis → decreased size, productivity, quality; mutations; loss of biodiversity |
| Aquatic Ecosystems | Phytoplankton (base of food chain) reduced → decreased fish productivity; damage to early development stages of aquatic animals |
| Materials | Increased degradation of polymers; damage to plastics, paints, and synthetic materials |
UN 2018 Report: Ozone layer is healing due to steps taken (decreased CFC use). Northern Hemisphere ozone should be completely healed by 2030s. Southern Hemisphere by 2050s. Since 2000, ozone layer has increased by 1–3% every decade.
SAQ 4: Ozone is present in the Stratosphere (15–50 km altitude), with peak concentration at about 25 km near the equator and about 15 km in polar regions. Peak concentration ~300 ppb.
SAQ 5: CFCs (Chlorofluorocarbons) are compounds containing chlorine, fluorine, and carbon atoms. Used as propellants in spray cans (shaving cream, hair spray, deodorants, paints, insecticides), in refrigeration, air conditioning, and blowing of foams. Harmful because: they are very stable in the troposphere (lasting 75–140 years), rise to the stratosphere, where UV radiation breaks them to release highly reactive chlorine atoms, which attack ozone (O₃) through chain reactions, depleting the ozone layer → more UV-B reaches Earth → skin cancer, cataracts, immune suppression, and crop damage.
SAQ 6: 16th September — International Day for the Preservation of the Ozone Layer, commemorating the signing of the Montreal Protocol on 16 September 1987. Declared by UN General Assembly in January 1995.
| Area | Effect |
|---|---|
| Crops and Plants | Dissolves minerals and nutrients from soil; kills soil bacteria and fungi → reduced soil fertility → stunted plant growth; can cause mutations in plants |
| Water Bodies | Lowers pH of lakes, rivers, and ponds; destroys aquatic life (plants, fish) — different species have different pH tolerances |
| Human Health | Acid gases cause lung and respiratory problems — asthma, bronchitis; dry deposition from air can cause heart and lung problems |
| Materials and Buildings | Corrodes metals, paints, plastics; damages limestone/marble buildings (CaCO₃ + H₂SO₄ → CaSO₄ + CO₂ + H₂O). Taj Mahal colour affected! Bridges, monuments, historical buildings at risk. |
Even in unpolluted environments, rain is slightly acidic — pH ~5.7. This is because atmospheric CO₂ dissolves in rainwater forming carbonic acid (H₂CO₃, a weak acid). Acid deposition = any precipitation with pH < 5.7. Acid rain has pH ~4. Long-range transport means acid precursors from one country can fall as acid rain in another → global issue. Taj Mahal in Agra is a prime example of acid rain damage in India.
SAQ 7: pH of normal (unpolluted) rain = ~5.7. This is because atmospheric CO₂ dissolves in rainwater forming weak carbonic acid (H₂CO₃). Acid deposition = pH < 5.7.
SAQ 8: Sulphuric acid (H₂SO₄) and Nitric acid (HNO₃). Formed by: SO₂ + O₂ + H₂O → H₂SO₄ ; NOₓ + H₂O → HNO₃. Both are strong acids.
SAQ 9: Marble buildings are made of calcium carbonate (CaCO₃). Acid rain (H₂SO₄) reacts with it: CaCO₃ + H₂SO₄ → CaSO₄ + CO₂ + H₂O. The calcium sulphate (CaSO₄) formed is soluble/crumbly and washes away, leaving the surface discoloured and eroded. The Taj Mahal's marble is visibly affected by this reaction.
Exam-style questions from the IGNOU textbook.
The greenhouse effect is a phenomenon where certain atmospheric gases trap heat, keeping Earth's surface warmer than it would otherwise be. About 1/3 of incoming solar radiation is reflected back into space, 20% is absorbed by atmospheric gases, and the remaining ~47% reaches Earth's surface and is absorbed. The absorbed energy is re-emitted as infrared (heat) radiation. Greenhouse gases (CO₂, CH₄, O₃, CFCs, water vapour) absorb this infrared radiation and do not allow all of it to escape into space — much like the glass walls of a greenhouse that trap heat inside.
The natural greenhouse effect raises Earth's average temperature from -18°C (without any GHGs) to +15°C — essential for life. The enhanced greenhouse effect occurs when human activities (burning fossil fuels, deforestation) increase GHG concentrations → more heat is trapped → global warming.
Climate change affects rainfall patterns and soil moisture. India's agriculture — largely dependent on the monsoon — would be seriously affected by changes in rainfall patterns. Crop yields would change → malnutrition and food price escalation. India also has a densely populated coastline: sea level rise threatens coastal communities with flooding and displacement. Natural disasters (cyclones, floods, droughts) would increase in frequency and intensity, causing loss of human lives and property.
India's economy depends on climate-sensitive sectors (agriculture, forestry). Warmer temperatures would expand the geographical range of vector-borne diseases like malaria and dengue. Himalayan glaciers, which feed major river systems (Ganga, Brahmaputra), are retreating — threatening water security for hundreds of millions.
India's response: NAPCC (2008) with 8 National Missions including National Solar Mission, National Water Mission, Mission for Sustaining the Himalayan Ecosystem, and Mission for Sustainable Agriculture. All States directed to prepare State-level Climate Action Plans.
Wet deposition = acids deposited in rain, snow, fog, mist, or dew. When sulphuric acid and nitric acid dissolve in rainwater, they lower its pH below 5.7 — forming acid rain. This washes directly into soil and water bodies.
Dry deposition = deposition of acidic particles and gases in the absence of moisture. These deposits settle on tree leaves, buildings, surfaces, and soil. When rain eventually washes them off, the acidity reaches soil and water bodies. Dry deposition is often underestimated but can be significant in areas far from emission sources (long-range transport).
Both types cause the same damage to ecosystems, human health, and materials — they are together termed "acid deposition."
Harmful effects of UV-B on human health: (1) Cataracts — opacity of the eye lens leading to blindness; (2) Skin cancer — UV-B damages DNA in skin cells → melanoma and other skin cancers; (3) Immune system suppression — UV-B reduces immune system effectiveness → increased susceptibility to infectious diseases (herpes, tuberculosis, other infections that immune system normally fights).
Ozone Hole: The depletion or thinning of the ozone layer is called the ozone hole. It was first pointed out in 1985 by the British Antarctic Survey which observed significant ozone depletion over Antarctica during spring. Data: ozone concentration dropped from ~300 DU in 1970 to ~200 DU in 1984, and as low as ~88 DU in 1994. This thinning allows more UV-B radiation to reach Earth's surface. Ozone depletion also confirmed over the Arctic and mid-latitude regions (USA, Europe). The Montreal Protocol (1987) was created to phase out ozone-depleting substances. Good news: the ozone layer is healing — Northern Hemisphere expected to recover by the 2030s, Southern Hemisphere by the 2050s.
Effects on Crops and Plants: Acid rain dissolves important minerals and nutrients from soil, killing bacteria and fungi needed for nutrient cycling and nitrogen fixation → reduced soil fertility → stunted plant growth. May cause plant mutations and reduced productivity.
Effects on Water Bodies: Accumulation of acid rain in lakes and rivers lowers pH over time → acidified water kills aquatic plants, insects, fish, and amphibians. Different species have different pH tolerance; as pH drops, species are progressively eliminated.
Effects on Human Health: Acid gases (SO₂, NOₓ) cause respiratory problems (asthma, bronchitis). Long-term exposure can cause heart and lung disease. Acid water dissolves heavy metals from soil → enters drinking water → health risks.
Effects on Materials: Acid rain corrodes metals (bridges, railings), degrades paints and plastics, and chemically attacks limestone and marble buildings (CaCO₃ + H₂SO₄ → CaSO₄ + CO₂ + H₂O). India's Taj Mahal in Agra is already visibly affected.
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