Almost 2 cm of sea level rise this century was due to melting glaciers, says study. Should you be concerned?

Coastal cities in India have also witnessed the sea level rise in recent years. Mumbai, for instance, has witnessed a rise of 4.44 cm between 1987 and 2021, the worst among Indian cities.

Hightide at the seaside Worli village in Mumbai. (Express Archive Photo by Pradeep Kocharekar)

5 min readNew DelhiFeb 23, 2025 01:03 PM IST First published on: Feb 22, 2025 at 06:54 AM IST

Melting ice from glaciers worldwide has led to the sea level rising by almost 2 cm this century alone, a newly-published study has found. Glaciers have been losing 273 billion tonnes of ice each year — equivalent to how much water Earth’s entire population would consume over a period of 30 years — for the last 25 years, the study reported.

While the 2 cm sea level rise may seem insignificant, it can have disastrous consequences for the world. Andrew Shepherd, head of the Department of Geography and Environmental Science at the UK’s Northumbria University told The Guardian: “Every centimetre of sea level rise exposes another 2 million people to annual flooding somewhere on our planet.”

The research paper titled ‘Community estimate of global glacier mass changes from 2000 to 2023’, was published in the journal Nature on February 19. It was carried out by scientists from the University of Edinburgh (Scotland) and the University of Zurich (Switzerland).

Why the sea level is rising

Sea level rise is essentially the increase in the average height of the ocean’s surface, measured from the centre of the Earth. There are two primary reasons why sea levels are currently rising.

FIRST is the global warming-driven melting of glaciers (accumulation of ice and snow that slowly flows over land) and ice sheets (glaciers which cover more than 50,000 square km of land). According to the latest study, since 2000, glaciers have lost between 2% and 39% of their ice regionally, and about 5% globally. This is roughly 18% more than the two existing ice sheets — in Greenland and the Antarctic — have lost in the same time period.

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SECOND is the thermal expansion of seawater, a process by which water expands as it warms up. With global temperatures rising, oceans are becoming warmer, and as a result, the volume of water is increasing as well. Thermal expansion of seawater is responsible for one-third to half of global sea level rise, according to the National Aeronautics and Space Administration (NASA).

The rise, in numbers

The global sea level has risen by about 21 cm since 1880, when records were first kept, according to the US agency National Oceanic and Atmospheric Administration (NOAA). However, in recent years, this rise has accelerated dramatically. It has more than doubled from 0.18 cm per year in 1993 to the current rate of 0.42 cm per year. Simply put, global sea levels have risen by more than 10 cm between 1993 and 2024, according to NASA, which says that the recent rate of increase is unprecedented over the past 2,500-plus years.

Notably, the sea level is not rising uniformly world over. For instance, the southwestern Indian Ocean region is seeing the sea level rise at a rate of 2.5 mm per year, faster than the global average, according to a 2022 World Meteorological Organization report.

The uneven rise is because “regional patterns of sea-level change are dominated by local changes in ocean heat content and salinity,” the report said.

Coastal cities in India have also witnessed the sea level rise in recent years. Mumbai, for instance, has witnessed a rise of 4.44 cm between 1987 and 2021, the worst among Indian cities, according to a 2024 report by a Bengaluru-based Center for Study of Science, Technology and Policy (CSTEP). For context, the island city has an average elevation of around 10 m above sea level, making it extremely vulnerable to future sea level rise. West Bengal’s Haldia has witnessed a sea-level rise of 2.726 cm, Andhra Pradesh’s Visakhapatnam 2.381 cm, and Kerala’s Kochi 2.213 cm, the CSTEP report said.

Why we should be concerned

An increase in sea level can severely impact both human and natural systems. It leads to more frequent and intense coastal flooding, which exacerbates coastal erosion, and ultimately displaces populations living close to the coast.

For instance, between 1990 and 2016, the West Bengal coast alone lost almost 99 sq km of land, according to a 2018 report by the National Centre for Coastal Research (NCCR). Sea level rise is a major contributor to this.

A 2024 study in the journal Scientific Reports found that 29% of the global population lived within 50 kilometers of shore in 2018, while 15% lived merely 10 km away from water.

The rise also results in more intense storm surges, allowing more water inland during tropical storms. This in turn can impact coastal ecosystems like mangroves, coral reefs and salt marshes, contaminate fresh water supplies, and thus affect people’s daily lives.

Studies have shown that the sea level will significantly rise if the world fails to curb the heat-trapping greenhouse gas emissions. In a 2024 statement, Nadya Vinogradova Shiffer, director of the NASA sea level change team and the ocean physics program in Washington, said, “Current rates of acceleration mean that we are on track to add another 20 cm of global mean sea level by 2050, doubling the amount of change in the next three decades compared to the previous 100 years and increasing the frequency and impacts of floods across the world.”