The Relative Mean Sea Level (RMSL) around coastal India is projected to rise by 0.5–1 metre by the end of this century and this is likely to be the main contributor to extreme sea-level rise along Indian coastlines, according to scientists at the Indian National Centre for Ocean Information Services (INCOIS).
Findings from their study suggest that climate change-induced hazards such as storm surges, waves, and tides may significantly contribute to end-of-century Extreme Sea Level (ESL) at specific locations along India’s coast. The coastal zones of the Gulf region in Gujarat are expected to be largely affected by changes in tidal amplitude, while changes in climate extremes could become a major source of ESL variation at Visakhapatnam in Andhra Pradesh.
“Our findings are based solely on various available global model simulations. They highlight multiple sources of uncertainty and the potential way forward to reduce those uncertainties,” said INCOIS Director T.M. Balakrishnan Nair in an exclusive interaction.
The rise in ESL poses a significant risk for India, given its extensive coastline of over 11,098.81 km, including the Andaman, Nicobar, and Lakshadweep Islands. Several low-lying areas lie within five metres of mean sea level, such as the deltaic regions in the northern Bay of Bengal, parts of Lakshadweep Islands, and expansive inter-tidal zones in Gujarat.
An interim report titled ‘Projected Climate Change-Induced Extreme Sea Levels and Coastal Vulnerability along the Indian Coasts’, prepared under the Ministry of Earth Sciences’ (MoES) “Deep Ocean Mission”, warns that rising sea levels could lead to beach retreat and erosion, permanent flooding of coastal areas, and loss of marine biodiversity.
The findings are significant because a large fraction of India’s population — over 350 million people — live near coastlines and depend heavily on the marine economy. A wide range of marine activities also dominate India’s maritime zone.
The study notes that the Global Mean Sea Level (GMSL) has already increased by 0.2 metres between 1901 and 2018 and is projected to rise by 0.5–1 metre by 2100. Future projections for the Indian coastline indicate a rise ranging from 0.62 metres at Visakhapatnam to 0.87 metres at Bhavnagar under a high-emission scenario, and from 0.40 metres (Visakhapatnam) to 0.63 metres (Bhavnagar) under a mid-emission scenario.
Present-day extreme sea levels along Indian coasts and islands are also projected to rise significantly — between 0.68 metres at Chennai and 1.12 metres at Bhavnagar under a high-emission scenario by 2100, and between 0.38 metres at Mumbai and 0.87 metres at Bhavnagar under a mid-emission scenario.
The relative mean sea-level rise remains the major contributor to extreme sea-level changes along Indian coasts, with additional contributions from tidal maxima (largest tidal amplitude increase of ~0.16 metres at Bhavnagar, Gujarat) and climate extremes (largest change of ~0.09 metres at Visakhapatnam). Coastal regions including the Gulf areas off Gujarat and the northern coasts of the Bay of Bengal are experiencing the largest changes in tidal and climate patterns.
The increase in greenhouse gas (GHG) concentrations, especially anthropogenic CO₂, continues to warm Earth’s climate, causing land ice (ice sheets and mountain glaciers) to melt and seawater to expand thermally. This results in an increase in ocean volume and mean sea-level rise across most global oceans.
According to the latest IPCC Sixth Assessment Report, the global mean sea level has been rising over the last century at a rate of 1.8 mm/year. Satellite observations over recent decades indicate an accelerated rise of ~3.2 mm/year in the early 21st century. Regional sea-level rise often deviates from the global mean due to ocean circulation and local Vertical Land Motion (VLM). Coastal sea levels are further influenced by tides, waves, and storm surges, making deterministic predictions of extreme coastal sea-level changes complex.
Scientists caution that global projections of extreme sea levels and their components still carry large uncertainties. Process modeling based on region-specific models, combined with sustained observations, may help reduce these uncertainty bounds. Therefore, there is an urgent need to assess projected changes in extreme sea levels along Indian coasts to enable better coastal zone management and policymaking.
In this report, scientists used currently available information on projected changes in relative mean sea level, tides, and climate extremes to assess end-of-century (year 2100) extreme sea-level changes along the Indian subcontinent and islands.
Other scientists involved in the study include Nidheesh A.G., Archit Wadalkar, Abhisek Chatterjee, Aneesh Lotliker, Mahendra R.S., Mohanty P.C., Ch Lakshmi Sravani, Padmanabham J., Francis P.A., Srinivasa Kumar T., and MoES Secretary Ravichandran M.
Published – November 24, 2025 08:06 pm IST
