Sea Level Rise — Revision Notes
⚡ 30-Second Revision
- Global average SLR: ~3.7 mm/year (2006-2018).
- Primary causes: Thermal expansion (~50%), melting land ice (glaciers, ice sheets).
- Key impacts: Coastal flooding, saltwater intrusion, erosion, displacement.
- India's vulnerable regions: Sundarbans, Mumbai, Chennai, Kochi.
- International frameworks: UNFCCC, Paris Agreement (Article 7, L&D Fund).
- Indian policies: CRZ Notifications, NAPCC.
- IPCC: Primary scientific authority for projections.
- Mnemonic: RISE Framework (Rate, Ice, Surge, Expansion).
2-Minute Revision
Sea level rise (SLR) is a critical climate change impact, driven primarily by the thermal expansion of ocean water and the melting of land-based glaciers and ice sheets. The global mean sea level has been accelerating, reaching approximately 3.
7 mm per year in recent decades, with IPCC projections indicating significant future increases. This phenomenon leads to severe consequences: increased coastal flooding and storm surge amplification, saltwater intrusion into freshwater aquifers and agricultural lands, and accelerated coastal erosion.
India, with its extensive coastline, is highly vulnerable, particularly regions like the Sundarbans, and major cities such as Mumbai, Chennai, and Kochi, which face threats of inundation and livelihood disruption.
International efforts under the UNFCCC and Paris Agreement aim to mitigate SLR through emission reductions and support adaptation, notably through the new Loss and Damage Fund. Nationally, India relies on policies like the Coastal Regulation Zone (CRZ) notifications and the National Action Plan on Climate Change (NAPCC) to manage coastal development and build resilience.
Understanding these mechanisms, impacts, and policy responses is crucial for UPSC, emphasizing both mitigation and adaptation strategies.
5-Minute Revision
Sea level rise (SLR) is a direct, accelerating consequence of global warming, primarily caused by two mechanisms: thermal expansion of ocean water and the melting of land-based glaciers and ice sheets.
As oceans absorb excess heat, water expands, contributing about 50% to observed SLR. The melting of vast ice sheets in Greenland and Antarctica, along with mountain glaciers, adds significant freshwater volume to the oceans.
The global mean sea level rise rate has accelerated from 1.3 mm/year (early 20th century) to approximately 3.7 mm/year (2006-2018), with recent data showing even higher rates. IPCC projections indicate a rise of several decimeters to over a meter by 2100, depending on emission scenarios.
The impacts of SLR are multi-dimensional: increased frequency and intensity of coastal flooding, amplified storm surges during extreme weather events, saltwater intrusion contaminating freshwater aquifers and agricultural lands, and accelerated coastal erosion.
These lead to displacement of populations, loss of livelihoods (fisheries, agriculture), damage to critical infrastructure, and degradation of vital coastal ecosystems like mangroves and coral reefs. India, with its 7,500 km coastline, is exceptionally vulnerable.
The Sundarbans faces existential threats, while metropolitan hubs like Mumbai, Chennai, and Kochi are at high risk of inundation and economic disruption. This creates 'Cascading Vulnerability Chains' where initial environmental impacts trigger a series of interconnected socio-economic and ecological crises.
International responses include the UNFCCC and the Paris Agreement, which aim to limit global warming and support adaptation efforts (e.g., Article 7). The operationalization of the Loss and Damage Fund at COP28 is a significant step towards climate justice for nations facing irreversible impacts.
India's national policies, such as the Coastal Regulation Zone (CRZ) notifications (e.g., CRZ 2018) regulate coastal development, while the National Action Plan on Climate Change (NAPCC) guides broader climate action, including coastal resilience.
Adaptation strategies range from hard engineering solutions (sea walls) to nature-based solutions (mangrove restoration) and managed retreat. For UPSC, a holistic understanding of the scientific basis, diverse impacts (especially India-specific), policy frameworks, and the challenges of implementation is vital, emphasizing integrated and adaptive governance.
Prelims Revision Notes
- Definition & Causes: — Sea level rise (SLR) is the increase in average ocean height. Primary causes: Thermal expansion (ocean warming, water expands) and melting of land-based ice (glaciers, Greenland/Antarctic ice sheets). Melting sea ice (e.g., Arctic) does NOT significantly contribute.
- Rates & Projections: — Global mean SLR: ~3.7 mm/year (2006-2018). IPCC AR6 projects 0.28-0.55m (low emissions) to 0.63-1.01m (high emissions) by 2100. Regional variations exist due to currents, gravity, land subsidence.
- Key Impacts: — Coastal flooding (nuisance flooding, storm surge amplification), saltwater intrusion (freshwater aquifers, agriculture), coastal erosion, permanent inundation, ecosystem degradation (mangroves, coral reefs), displacement.
- India-Specific Vulnerability: — Long coastline, dense population. Highly vulnerable: Sundarbans (erosion, salinity, mangrove loss), Mumbai (low-lying, dense infrastructure), Chennai (storm surge, saltwater intrusion), Kochi (backwater ecosystems). Other states: Gujarat, Odisha, West Bengal.
- International Frameworks: — UNFCCC (overall climate action), Paris Agreement (Article 7 on adaptation, NDCs), IPCC (scientific assessments), Loss and Damage Fund (COP28).
- Indian Policies: — Coastal Regulation Zone (CRZ) Notifications (1991, 2011, 2018) – regulate coastal development. National Action Plan on Climate Change (NAPCC) – strategic missions for climate resilience. MISHTI scheme (mangrove restoration).
- Adaptation Strategies: — Hard engineering (sea walls), nature-based solutions (mangroves), managed retreat, early warning systems.
- Key Concepts: — Thermal expansion, ice sheet dynamics, saltwater intrusion, CRZ, SSPs, storm surge amplification, MISI.
Mains Revision Notes
- Conceptual Framework: — Understand SLR as a 'Cascading Vulnerability Chain' – initial physical impacts (flooding, erosion) trigger socio-economic (displacement, livelihood loss, food/water insecurity) and ecological (ecosystem degradation, biodiversity loss) crises, creating feedback loops.
- Multi-Dimensional Impacts (India Focus):
* Environmental: Coastal erosion, permanent inundation, saltwater intrusion (agriculture, drinking water), ecosystem loss (mangroves, coral reefs). * Socio-economic: Mass displacement, climate refugees, loss of traditional livelihoods (fishing, farming), infrastructure damage (ports, cities like Mumbai/Chennai), economic costs of adaptation/reconstruction.
* Disaster Management: Amplification of extreme weather events (cyclones, storm surges) due to higher baseline sea levels, straining disaster response.
- Policy Analysis (International & National):
* International: UNFCCC & Paris Agreement (mitigation targets, adaptation goals, NDCs). IPCC (scientific basis). COP28 & Loss and Damage Fund (climate justice, financial support for irreversible impacts).
Limitations: insufficient finance, enforcement gaps, equity issues. * National (India): CRZ Notifications (evolution, effectiveness, challenges in enforcement, need for climate-integrated planning).
NAPCC (missions like NMSHE, NMSH). Nature-based solutions (MISHTI). Disaster preparedness frameworks.
- Adaptation & Mitigation Strategies:
* Mitigation: Global emission reductions (India's LT-LEDS). * Adaptation: Hard engineering (sea walls), nature-based solutions (mangrove restoration, coral protection), managed retreat (strategic relocation), early warning systems, climate-resilient infrastructure, community-based adaptation.
- Critical Examination: — Discuss challenges like funding, technology transfer, inter-agency coordination, socio-economic barriers to adaptation, and the ethical dimensions of climate justice. Emphasize the need for integrated coastal zone management (ICZM) that incorporates climate change projections and community participation.
- Current Relevance: — Integrate recent events (IPCC AR6, COP28, specific cyclones in India, updated SLR rates) to demonstrate contemporary understanding.
Vyyuha Quick Recall
The RISE Framework for Sea Level Rise:
Rate: Remember the accelerating global average rate, approximately 3.7 mm/year in recent decades. Ice: Focus on the melting of land-based Ice (glaciers and ice sheets) as a major contributor. Surge: Understand how higher sea levels amplify Storm Surges during extreme weather events. Expansion: Recall Thermal Expansion of ocean water as it warms, increasing its volume.