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The Alarming Rise of Global Sea Levels
Context:
The study titled “Community estimate of global glacier mass changes from 2000 to 2023“, published in Nature on February 19, found that glaciers have lost between 2% and 39% of their ice regionally, with a global loss of about 5%.
Glacial Ice Loss and Sea Level Rise
- Glaciers worldwide have been losing 273 billion tonnes of ice annually for the last 25 years, which is equivalent to the amount of water the entire global population would consume over 30 years.
- This melting has caused global sea levels to rise by nearly 2 cm this century. Although 2 cm might seem small, the consequences are significant.
- Andrew Shepherd, a leading expert from Northumbria University, explained that each centimetre of sea level rise exposes 2 million people to annual flooding.
Why Sea Levels Are Rising?
- Glacier Melting: The loss of ice from glaciers and ice sheets, particularly in regions like Greenland and Antarctica, contributes significantly to rising sea levels.
- Thermal Expansion: As global temperatures rise, the oceans warm up, causing seawater to expand. This process contributes to one-third to half of global sea level rise, according to NASA.
Current Sea Level Trends
- Global Sea Level Rise: Since 1880, global sea levels have risen by approximately 21 cm (NOAA). However, the rate of increase has accelerated dramatically.
- 1993: Sea level was rising at 0.18 cm per year.
- 2024: The rate has more than doubled to 0.42 cm per year, which has led to more than 10 cm of rise since 1993.
- This acceleration is unprecedented over the past 2,500 years.
Regional Variations
- Southwestern Indian Ocean: This region is rising at a rate of 2.5 mm per year, faster than the global average.
- Coastal Cities in India: Cities like Mumbai, Haldia, Visakhapatnam, and Kochi have witnessed significant sea-level rises. For example:
- Mumbai has seen 4.44 cm of rise from 1987 to 2021.
- Haldia: 2.726 cm
- Visakhapatnam: 2.381 cm
- Kochi: 2.213 cm
Impact of Rising Sea Levels
- Flooding and Coastal Erosion: Increased sea levels result in more frequent and severe coastal flooding and erosion, displacing populations living near the coast. For instance, between 1990 and 2016, West Bengal lost nearly 99 sq km of land due to sea-level rise.
- Coastal Ecosystems: The rise impacts ecosystems like mangroves, coral reefs, and salt marshes, as well as freshwater supplies.
- Storm Surges: Rising sea levels lead to stronger storm surges, increasing the inland spread of water during tropical storms.
Future Projections
- A 2024 study in Scientific Reports found that:
- 29% of the global population lived within 50 km of the shore (2018).
- 15% lived just 10 km away.
- NASA’s Nadya Vinogradova Shiffer warns: At current acceleration rates, another 20 cm rise by 2050 is expected. This would double the sea level rise in just 30 years compared to the previous century.
- More frequent and intense floods worldwide.
