Why are sea levels rising?

Rising oceans are posing a global threat, particularly to low lying islands and coastal cities. Countries like Tuvalu, Maldives, etc would be gravely affected due to sea-level rising

Background

• United Nations Report: The UN report titled “Surging Seas in a Warming World” states that “Global-mean sea level is rising and accelerating as a direct consequence of human-induced global warming. This rise in sea level is driven primarily by two factors: the melting of land ice and  the expansion of seawater as it warms.”
• UN General Assembly High-Level Meeting: United Nations General Assembly (UNGA) held a high-level plenary meeting on sea level rise in September 2024. The overall theme of the high-level meeting was “Addressing the threats posed by sea-level rise”.
• Tonga: “The ocean is overflowing,” warned United Nations secretary general Antonio Guterres at a recent visit to Tonga. The South Pacific archipelago (Tonga) is among several countries in the region facing severe and disproportionate threats from rising sea levels. While low-lying islands are especially at risk, numerous coastal communities and cities globally are already contending with increasingly destructive floods and storms, jeopardising lives, jobs, and essential infrastructure.

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Rising Sea-Levels (Data): Since records began in 1880, they have risen more than 20 cm (more than 8 inches), and this is getting faster with each decade. Brent Minchew, an MIT geophysicist who studies glaciers and oceans says the worst-case scenario is that the sea level rise by the end of the century reaches 2 metres (200 cm)

• According to the World Meteorological Organization, in 2023, global mean sea level reached a record high in the satellite record (since 1993), reflecting continued ocean warming (thermal expansion) as well as the melting of glaciers and ice sheets.
• The rate of global mean sea level rise in the past ten years (2014–2023) is more than twice the rate of sea level rise in the first decade of the satellite record (1993–2002).

Why Are Sea Levels Rising? 

• Global Warming: Sea level is driven by global warming, caused by carbon dioxide, methane and other emissions released from the burning of fossil fuels for uses including energy, industry, and transport. 
  • Future Threats: With the current situation we are on a path to 2.7 degrees Celsius rise in temperature by the end of the century. This would lead to a further rise of 56 cm.
  • If the world holds it below 1.5 degrees Celsius as set out in the Paris Agreement and hits net zero emissions by 2050, global sea levels are set to rise a further 38 cm by 2100.
• Ocean Heats Up: Global warming  is making the ocean heat up. 
  • Data: Our seas have absorbed an estimated 90% of atmospheric warming over the past 50 years, and the pace of ocean heating has doubled in the last 20 years, rising three times faster than the global average in the southwest Pacific Sea. Ocean temperatures in 2023 were the hottest on record.
  • Thermal Expansion: When water heats up, it grows in volume due to a process known as thermal expansion. 
• Melting Ice Sheets: One of the major sources of sea level rise is the melting of ice sheets and mountain glaciers due to increasing heat.
  • Data: An average of 150 billion tons of ice mass are lost yearly from Antarctica and 270 billion tons from Greenland.
• Albedo Effect: Melting of ice sheets leads to albedo effect which leads to more ice melt which increases the sea level.

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Threats Posed by Rise in Sea Level

• Impact on Populated Coastal Regions and Megacities: The rise in sea levels poses a significant threat to populated coastal regions and megacities across the globe. For every centimeter of sea level rise, an additional 6 million people are estimated to be at risk of coastal flooding. According to a 2022 study, tropical regions, particularly in Asia, are among the hardest hit, with countries like Bangladesh, India, and China facing severe risks. Megacities such as Cairo, Lagos, Los Angeles, Mumbai, Buenos Aires, and London are also expected to experience serious impacts, threatening their infrastructure, economy, and the safety of millions of residents.
• Existential Threat to Low-Lying Islands: Low-lying small islands, including Fiji, the Maldives, and Tuvalu, face some of the most critical threats from rising sea levels. Even a moderate increase in sea level could pose an existential danger to these islands, as they are particularly vulnerable to inundation. With nearly 40% of the world’s population living near the coast and approximately 900 million people in low-elevation zones, the global impact of sea level rise is profound, threatening the livelihoods, homes, and survival of millions worldwide.

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What Can be Done to Respond?: 

• Emission Reduction: The solution to preventing dramatic sea level rise lies in rapidly reducing carbon emissions. The global community has committed to achieving net-zero energy-related carbon dioxide emissions by 2050, aiming to provide a viable chance of limiting the rise in global temperature to 1.5 °C. This ambitious goal is crucial in combating the effects of climate change, including rising sea levels, which threaten coastal communities worldwide.
• Global Adaptation Strategies: Countries around the globe are implementing a variety of adaptation measures to cope with the impacts of rising sea levels. These measures range from constructing sea walls and storm surge barriers to improving drainage systems and developing flood-resistant buildings.
  • Nature-Based Solutions: Some adaptation strategies are simpler and nature-based, such as staving off coastal erosion by driving wooden stakes into the beaches of Senegal or regenerating mangrove forests in Cameroon, which act as natural buffers against storm surges. These environmentally friendly approaches not only protect coastlines but also support local ecosystems.
• Low-Lying Island States: For low-lying small island states, responses to sea level rise include relocating entire villages to higher ground in Fiji, building floating cities in the Maldives, and reclaiming land from the sea in Tuvalu. However, many developing regions require financial assistance to effectively address the consequences of sea level rise and other climate change impacts, emphasizing the need for global support and collaboration in the face of this pressing challenge.

Conclusion

Rising sea levels pose a significant threat to coastal communities worldwide, exacerbating the risks of floods and storms. Immediate and sustained efforts are crucial to mitigate these impacts and protect vulnerable populations and infrastructure.

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