A recent scientific study conducted by the Indian National Centre for Ocean Information Services (INCOIS) has projected a significant rise in the Relative Mean Sea Level (RMSL) along India's extensive coastline by the end of this century. According to the findings, the RMSL is expected to increase by approximately 0.5 to 1 metre by 2100, posing serious challenges for coastal regions across the country. This rise is identified as the primary driver behind extreme sea-level (ESL) events along India’s shores, which include storm surges, tidal fluctuations, and waves intensified by climate change.
India’s coastline, stretching over 11,000 kilometres and encompassing mainland shores as well as island territories such as the Andaman, Nicobar, and Lakshadweep Islands, is home to more than 350 million people. Many of these coastal populations live in low-lying areas within five metres of the current mean sea level, including vulnerable deltaic regions in the northern Bay of Bengal, parts of Lakshadweep, and the extensive inter-tidal zones of Gujarat. These zones face heightened risks of erosion, permanent flooding, and loss of marine biodiversity as a consequence of rising sea levels.
The study, titled ‘Projected Climate Change-Induced Extreme Sea Levels and Coastal Vulnerability along the Indian Coasts,’ was prepared under the Ministry of Earth Sciences' (MoES) Deep Ocean Mission. It highlights how climate-driven factors such as increasing storm surges and changes in tidal patterns could exacerbate the severity of ESLs at specific locations. For instance, the Gulf region of Gujarat is anticipated to experience significant changes in tidal amplitude, while Visakhapatnam on the eastern coast may see ESL variations largely influenced by climate extremes like intensified storms.
INCOIS Director T.M. Balakrishnan Nair emphasized that the study’s projections are derived from various global climate and ocean model simulations, which inherently contain uncertainties. He pointed out the need to refine these models and incorporate more region-specific data to improve accuracy in predicting future sea-level changes. Despite these uncertainties, the report serves as a crucial warning about the potential magnitude of coastal hazards that India may face if greenhouse gas emissions continue unabated.
Globally, the mean sea level has already risen by approximately 0.2 metres between 1901 and 2018, a trend primarily driven by thermal expansion of seawater and melting land ice resulting from global warming. The Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report notes that the rate of sea-level rise has accelerated from 1.8 millimetres per year over the last century to about 3.2 millimetres per year in recent decades. This warming and ice melt are directly linked to increasing greenhouse gas concentrations, especially carbon dioxide produced by human activities.
For India’s coastline, projections under different emission scenarios indicate varying degrees of sea-level rise by 2100. Under a high-emission pathway, sea levels are expected to rise between 0.62 metres at Visakhapatnam and 0.87 metres at Bhavnagar, Gujarat. Under a more moderate emission scenario, the rise is estimated between 0.40 metres and 0.63 metres for these locations respectively. Importantly, the ESL—which combines mean sea level with episodic events like tides and storm surges—is projected to increase even more sharply. For instance, by 2100, Chennai could see an ESL rise of 0.68 metres, whereas Bhavnagar could witness a rise of up to 1.12 metres under the high-emission scenario.
The study further identifies that while the overall rise in RMSL is the dominant factor in ESL increases, other contributors such as changes in tidal maxima and intensified climate extremes also play significant roles. In Gujarat’s Gulf region, tidal amplitude may increase by as much as 0.16 metres, while at Visakhapatnam, changes in climate extremes could add roughly 0.09 metres to ESL. These localized variations underscore the complexity of sea-level rise impacts, which are influenced by regional oceanographic and meteorological conditions.
Adding to the complexity is the phenomenon of Vertical Land Motion (VLM), where land subsidence or uplift alters local sea levels relative to the land, sometimes exacerbating the effects of ocean water level changes. Indian coasts are subject to varying degrees of VLM, further complicating predictions and necessitating detailed regional studies.
The consequences of rising sea levels for India are profound. Coastal