Key Points at a Glance

These key points give a compact, exam-ready map of the major environmental issues that RAS answers most often need: climate change, ozone depletion, biodiversity loss, desertification, plastic pollution, deforestation, ocean change, air pollution, and international environmental law. According to the World Meteorological Organization's State of the Global Climate 2024, 2024 was the warmest year in the 175-year observational record, with global mean near-surface temperature 1.55 ± 0.13°C above the 1850-1900 average.

1. Climate change: Global average temperature has risen sharply above pre-industrial levels; the WMO placed the 2024 annual anomaly at 1.55 ± 0.13°C above the 1850-1900 average, while long-term warming averaged over decades remains below 1.5°C. CO₂ concentration reached 423.9 ppm in 2024 in WMO greenhouse-gas monitoring, against about 280 ppm pre-industrial. 2023 was the warmest year then recorded, but 2024 superseded it as the warmest year in the 175-year observational record. The Paris Agreement (2015) set targets of limiting warming to 1.5°C (aspirational) and 2°C (maximum) above pre-industrial levels.

2. Ozone layer depletion — PYQ 2023 (10 marks): The ozone layer (stratosphere, 15–35 km altitude) absorbs 97–99% of the Sun's harmful UV-B and UV-C radiation. Ozone-depleting substances (ODS): CFCs (chlorofluorocarbons), HCFCs, halons, carbon tetrachloride — mainly from refrigerants, aerosols, fire extinguishers. The Antarctic Ozone Hole was discovered in 1985 (British Antarctic Survey). The Montreal Protocol (1987) — called the most successful international environmental agreement — has reduced ODS by 99%.

3. Biodiversity loss: Earth is experiencing its 6th mass extinction — current extinction rate is 100–1,000× the natural background rate. The current IUCN Red List has assessed 169,420 species; 47,187 are threatened (about 28%). Three major causes: habitat destruction (most significant — 80% of threatened species impacted), overexploitation (hunting, fishing), invasive species.

4. Desertification is the degradation of drylands due to human overuse and climate change. Affects 40% of Earth's land (dryland areas). Around 3.2 billion people are affected. Annual cost: ~$490 billion in lost productivity. UNCCD (UN Convention to Combat Desertification, 1994) is the global framework. Rajasthan relevance: Western Rajasthan faces severe desertification — dunes advancing 0.5–1.5 km/year before check dams and agroforestry.

5. Plastic pollution: Over 400 million tonnes of plastic produced annually (2023). Only 9% of all plastic ever produced has been recycled; 22% mismanaged. Microplastics (< 5 mm) found in deepest ocean (Mariana Trench), Arctic snow, human blood, and placenta. The Global Plastics Treaty (2024) — UN member states negotiating a binding treaty to end plastic pollution. India's single-use plastic ban (2022).

6. Deforestation: The world loses approximately 4.7 million hectares of forest annually (net, after reforestation). The Amazon Rainforest (Brazil) has lost 18–20% of its original cover since 1970 — concern about reaching a tipping point (~25%) beyond which the forest collapses into savanna (dieback). REDD+ (Reducing Emissions from Deforestation and Forest Degradation) is the UN mechanism for forest conservation.

7. Ocean acidification: Oceans absorb ~30% of all CO₂ emissions. This forms carbonic acid (H₂CO₃) → ocean pH has dropped from 8.2 to 8.1 (0.1 unit = 26% more acidic since pre-industrial times, due to logarithmic scale). Dissolves coral skeletons (CaCO₃) → coral bleaching and reef death. Threatens 25% of all marine species that depend on coral reefs.

8. Sea level rise: Global mean sea level has risen ~20 cm since 1900; recent satellite-era rise has accelerated, with WMO reporting 4.7 mm/year during 2015–2024. Two causes: thermal expansion (60–70%) of ocean water as it warms; ice melt from glaciers, Greenland, and Antarctica (30–40%). Pacific Island nations (Tuvalu, Kiribati, Maldives) face existential threat. India: Mumbai, Kolkata, Chennai, Kochi vulnerable.

9. Glacial retreat: Global glaciers losing ~31 billion tonnes of ice annually (2000–2019 data). Himalayan glaciers (India's "Water Tower") are retreating at accelerating rates; key example: Gangotri Glacier retreating ~22 m/year. UN 2025: International Year of Glaciers' Preservation.

10. Transboundary air pollution: PM2.5 (fine particulate matter <2.5 µm) is the most lethal air pollutant — causes cardiovascular and respiratory disease; ~7 million deaths/year globally (WHO). India's National Clean Air Programme (NCAP) targets 40% reduction in PM10 levels or achievement of the national standard by 2025–26 against the 2017–18 baseline. Delhi's AQI regularly breaches 400+ in winter (hazardous threshold: 300+).

11. Key international environmental agreements:

• Stockholm Conference (1972): First UN environment conference; led to UNEP creation
• Montreal Protocol (1987): Phase-out of ODS; most successful — ozone layer recovering
• Kyoto Protocol (1997): First binding GHG reduction targets; Annex I countries
• Paris Agreement (2015): 1.5–2°C warming limit; NDCs; all 195+ countries
• CBD (Convention on Biological Diversity, 1992): Biodiversity conservation; Nagoya Protocol (2010) on Access and Benefit Sharing
• Kunming-Montreal Agreement (2022): "30×30" — protect 30% of land and ocean by 2030

12. India's environmental commitments: NDC under Paris Agreement targets: Net Zero by 2070; 50% electric power installed capacity from non-fossil fuel-based energy resources by 2030; 45% reduction in emissions intensity by 2030 (vs 2005). National Action Plan on Climate Change (NAPCC, 2008) — 8 missions including National Solar Mission, National Water Mission, Green India Mission.

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