과학/건강

Sea level rise is not just a number; it's a physical process that connects mountains, rivers, and cities in a single line. As ice in the Himalayas and Andes melts and flows into the sea, sea levels rise, and the ocean, in turn, pushes into deltas and coastal cities. In this process, land is submerged, groundwater becomes saline, and people lose their homes. This is why mountain floods in Nepal are not unrelated to seawalls in Korea.

Submerged land, shrinking territory

The most direct consequence of sea level rise is submerged land. Geographies with low elevations or those composed of deltas and coral islands, such as Bangladesh, the Maldives, Indonesia, Florida in the United States, and the Netherlands, will experience significant reductions in area even with a slight increase in water levels. In Bangladesh, it is estimated that if sea levels rise by 1 meter, a significant portion of the country, approximately 11-18% according to some studies, could be permanently or repeatedly inundated. This country is already vulnerable to monsoon floods. As sea levels rise, drainage at river mouths is blocked, and inland flooding persists longer. For island nations like the Maldives, where most of the land is only a few meters above sea level, there are repeated warnings that an 80% loss of land could occur with just a 1-meter rise. The Marshall Islands, Tuvalu, and Kiribati face similar structural risks.

Major cities are no exception. The IPCC's Sixth Assessment Report estimates that global average sea levels are likely to rise by approximately 0.3-0.6 meters under a low-emission pathway and 0.6-1.0 meters under a high-emission pathway by 2100, based on the period 1995-2014. Including processes with low certainty, such as ice sheet instability, the upper end of the high-emission scenario could exceed 1 meter. At this level, major coastal cities like New York, New Orleans, Shanghai, Mumbai, and Jakarta would be exposed to constant flood risk. Venice already experiences 'acqua alta' as a daily occurrence, and a significant portion of the Netherlands is below sea level, relying on dikes and pumping systems. Jakarta is experiencing a combination of land subsidence and sea level rise, which is destabilizing the city's functions.

Saltwater encroaching on deltas, cracks in the food basket

The Mekong Delta in Vietnam is where this problem extends to the food system. This delta accounts for about half of Vietnam's rice production and about 90% of its exports. According to scenarios from Vietnam's Ministry of Natural Resources and Environment, sea levels in the Mekong estuary could rise by about 23 cm by 2050 and 55 cm by 2100 under RCP 4.5, and by about 28 cm by 2050 and 77 cm by 2100 under RCP 8.5. As seawater pushes upstream and into aquifers, salinity easily exceeds the limits that crops can withstand. Some reports indicate that salinity has soared to 4 grams per liter, four times the permissible level. Rice is vulnerable to salinity. If yields plummet or cultivation becomes impossible, the damage will spread beyond Vietnam's domestic prices to the international rice market.

Saltwater intrusion is not just a problem for the Mekong. Large deltas like the Ganges-Brahmaputra, Nile, and Irrawaddy have high population densities and agricultural dependence. When arable land shrinks and water sources are contaminated, livelihoods collapse. Water purification costs rise, and the poor must drink salty water or fetch water from further away. This burden is often shifted to the labor of children and women. The structure where low-income countries and classes, who emit less greenhouse gases, are hit first is precisely the core of climate justice.

Uninhabitable land and cross-border migration

As uninhabitable land increases, populations move. In Pacific island nations, national-level migration is already being discussed. Tuvalu and Kiribati are exploring migration agreements with Australia and New Zealand, or even considering ways to preserve their nationality and sovereignty through the concept of a digital nation. In continental countries like Bangladesh, coastal and delta residents are pushed into inland metropolises like Dhaka. If housing, jobs, and infrastructure burdens are compounded in already overcrowded cities, social tensions can escalate into political instability. The problem is the law. The current Refugee Convention is based on war and persecution. People who lose their homes due to climate change are left in a blind spot of protection.

The rock and glacier collapse near Langtang Lirung on the Nepal-Tibet border in August 2026 and the floods in the Bhotekoshi basin brought this issue to the forefront. Even by official counts, the death toll exceeded 1,400, with thousands more missing. The Nepalese government classified this as a climate disaster, holding countries with large historical and current emissions, such as the United States, China, and India, accountable and demanding compensation from the UN Loss and Damage Fund. The saying, “Mountain dwellers pay the price for fossil fuels burned far away,” is not just rhetoric. Who will accept climate refugees and by what criteria, and how border controls and immigration policies will be reorganized, are variables that will shape international politics for decades to come.

Questions posed by the coastline of the peninsular nation of Korea

Korea is not exempt from this chain of events. For a peninsular nation surrounded by sea on three sides, rising sea levels are not an abstract global problem but a design standard issue for ports, industrial complexes, power plants, and reclaimed land. The Korea Meteorological Administration's recent high-resolution ocean scenarios suggest that under a high-carbon pathway, sea levels around the Korean Peninsula could rise by generally 50-60 cm by the end of the 21st century. Previous CMIP5-based projections for RCP 8.5 estimated an average of about 65 cm, with the upper uncertainty limit exceeding 90 cm. The west coast has large tidal ranges and gentle slopes. Areas like Incheon/Songdo, Pyeongtaek/Dangjin, Gunsan, and Saemangeum, which rely on seawalls and drainage pumps, experience rapidly escalating damage when high tides and typhoons coincide. This is why we must re-evaluate whether current design flood levels and pump capacities can withstand end-of-century conditions.

Food and energy are also tied to the coast. While Korea has a high self-sufficiency rate for rice, it heavily relies on imports for wheat, soybeans, and feed grains. If breadbaskets like the Mekong and Nile are shaken by salinization and flooding, international grain price fluctuations will translate into domestic price increases. Coastal thermal and nuclear power plants and LNG terminals are exposed to storm surges and changes in intake water levels. Rising sea levels are not just a task for disaster prevention departments but an issue that simultaneously reconfigures industrial location, energy security, and food strategy.

Why the collapse that began in the mountains is completed at sea

The Peruvian Andes are also flashing the same warning signs. A recent study by Peru's National Institute for Research on Glaciers and Mountain Ecosystems (INAIGEM) found that approximately 59% of glacier area has disappeared in the last 60 years, and there are 528 glacial lakes at risk of overflowing. If these lakes burst, the damage will be concentrated in mountain villages and downstream agricultural lands. A significant amount of greenhouse gases comes from developed and emerging major countries, but the sites of disaster first appear on mountaintops, deltas, and coral islands. The 'climate stratification,' where high ground inside dikes is protected and low ground outside dikes suffers repeated flooding, is a urban version of the same logic.

Although the Loss and Damage Fund has been launched, criticisms of its insufficient scale and accessibility are repeated. The rapid assistance requested by Nepal is only a tiny fraction of the estimated damage. Nevertheless, this request is important because it is an attempt to shift climate disasters from a matter of charity to one of responsibility.

Glaciers are not just scenery; they are Earth's infrastructure that has sustained water, energy, and food. The process of mountain ice flowing into the sea and the sea engulfing cities has already begun. The choice is simple: rapidly reduce emissions to slow the rate of increase, and simultaneously create systems for defense, migration, and compensation for the risks that are already submerged. The collapse in Nepal, the lakes in Peru, the salinity in the Mekong, and the seawalls on the west coast are not different places but a single chain. Where to break that chain is a matter of the time we still have left.