There are few sights as magnificent and as readily available to the rich and poor alike in space-starved Mumbai as standing on Marine Drive at sundown and looking into the Arabian Sea. As you turn around, rows of art deco buildings with ship deck-like balconies greet you — part of a collection of structures that were accorded the Unesco World Heritage status last year.As you walk along the promenade in the southern end of the city, relishing the breezy reprieve after the onslaught of humidity through the day, it is hard to believe that this neighbourhood, home to some of the country’s priciest properties, stands on land reclaimed from the sea a century ago. It is harder still to picture it being reclaimed back by the ocean in about three decades, as a recent global study on the rise in sea levels predicted.Every new report tends to bring the imminent dangers of a warming planet closer and paints a more alarming picture than before, and this one is no different. Besides raising questions about the future of millions living on or near our coasts, climate change also places in danger economic activity such as agriculture, industry and tourism, impairing the economy. It could also deal a blow to vital infrastructure such as ports, and affect freshwater resources at a time of growing water scarcity.The projected 2050 map of Mumbai, a city of 18.4 million people, by the USbased science organisation Climate Central, shows several parts of the city submerged, including such landmarks as the headquarters of the city’s municipal corporation, the Reserve Bank of India, the Chhatrapati Shivaji Maharaj Terminus, Oval Maidan and Brabourne Stadium. Atul Kumar, a financial services professional who lives on Marine Drive, says people are genuinely concerned about what could happen. “We cannot deal with this issue in a confrontational way, like building barriers.” He adds on a lighter note that residents are calculating how old they will be by 2050 and whether they will be around to see the doomsday projection come true.Kumar also runs an organisation that is documenting art deco structures around the city.The Climate Central study, published in the journal Nature Communications, expects areas inhabited by 36 million Indians now to be at risk of chronic flooding by 2050, much higher than the five million expected previously. Globally, the figure could be as high as 300 million people, nearly four times the past estimations.By 2100, lands inhabited by 200 million people could permanently be below the high-tide line.These alarming numbers are despite the study using older population data and assuming a moderate reduction in emissions, which means the actual landfall, figuratively speaking, could be worse. “When you have a cyclone coming, every day of warning can save lives and property. But sealevel rise is slower so every decade of warning has the potential to save neighbourhoods and billions of dollars,” says Benjamin Strauss, chief executive of Climate Central and the study’s co-author.The 2015 Paris Agreement on climate change aims to limit the temperature increase by 2100 to under 2 degree Celsius above pre-industrial levels, while trying to limit it further to 1.5 degree Celsius.As part of its commitment under the agreement, India plans to cut emissions relative to its gross domestic product by a third by 2030 from 2005 levels. But the world is not on track to meet its emission-reduction targets and India’s renewable energy programme, integral to its climate goals, has lately come under strain. The United States is set to pull out of the agreement.Though Climate Central’s projections for the US and Australia are more reliable than for countries like India, where data on land elevation near the sea may not be as accurate, it is hard to ignore its warnings. Earlier this week, Antonio Guterres, secretary general of the UN, cited the report to say that the most vulnerable areas to rising sea levels are in Japan, China, Bangladesh and India. Sekar Kuriakose, member secretary, Kerala Disaster Management Authority, says the report has not examined local climate patterns. “But I wouldn’t rule it out. I see it is a cautionary note, like the warning on cigarette packs, and we are already smokers.”India’s coastline extends over 7,500 km across nine states, two Union territories and two island territories — Andaman & Nicobar and Lakshadweep.There are 171 million people — a seventh of India’s population — living in 70 coastal districts in these states and territories, and there are 14.5 million people dependent on fishing, according to government data. Four of India’s 10 most populated cities are on or near the coast.Rising sea levels certainly do not bode well for them. “Sea-level rise is long term and irreversible.Adapting to it will be the most expensive and difficult among climatic hazards,” says NH Ravindranath, a professor at the Indian Institute of Science in Bengaluru.Sea levels rise because water expands as the ocean warms and also due to the melting of glaciers and ice sheets. The oceans are said to be absorbing more than 90% of the excess atmospheric heat caused by greenhouse gas emissions. Rising seas mean storms travel further inland and more frequent flooding is caused by high tides. It exacerbates coastal erosion, contaminates the soil, affects groundwater resources and inundates wetlands, which act as protective barriers against storms and floods.The annual global mean sea level rise between 2006 and 2015 was 3.6 mm, which was two and a half times the figure between 1901 and 1990, according to an Intergovernmental Panel on Climate Change report in September 2019. It is set to increase further — 4-15 mm annually — by 2100, depending on the rate of decline in carbon emissions. Extreme sea-level events that are historically rare could occur once a year at many places by 2050 in all emission-reduction scenarios, especially in tropical regions like India.Sea-level trends vary across India. For instance, the sea level at Diamond Harbour near Kolkata has risen at a rate of more than 4 mm a year between 1948 and 2013, compared with just over 1 mm annually during a similar period in Vishakapatnam, according to the US National Oceanic and Atmospheric Administration.The east coast has historically been more vulnerable to cyclones than the west coast. According to the Indian Meteorological Department, the Bay of Bengal has had 520 cyclones between 1891 and 2018, compared with 126 in the Arabian Sea.Rising sea levels threaten coastal destinations which are already popular among tourists, such as Goa and Kerala, and the ones which are aspiring to be, like Odisha and Andhra Pradesh.In 2017, Goa attracted eight times the number of foreign tourists as Odisha, despite being a much smaller state, according to the tourism ministry. Data on tourist visits to beaches across India is not available.The Centre is spending Rs 2,000 crore to develop 17 coastal tourist hubs, including in Kakinada in Andhra and Gopalpur in Odisha. But these plans cannot afford to ignore the impact of climate change and have to promote sustainable tourism. In the temple-town of Puri in Odisha, which was ravaged by Cyclone Fani earlier this year, several hotels and other structures found to be encroaching on the beach were demolished five years ago.Raj Kishore Patra, who owns a hotel opposite the Puri beach, says the water comes in further during high tide than about a decade ago and hopes that there isn’t another cyclone like Fani in the near future. “What will happen in the future is in nobody’s hands.” He suffered damages worth Rs 2.5 crore to his hotel. It is hard to attribute any one event to climate change, but evidence is growing on the links between climate change and the intensity and frequency of cyclones, flooding and rainfall.Following the unprecedented floods of 2018 in Kerala, resorts in the state are now being built on stilts, and residents are following suit, says Kuriakose. Kerala has also sought to relocate 18,000 households which fall within 50 metres of the sea by offering them Rs 10 lakh each. But so far, only 2,000 have agreed as many find the compensation inadequate.There are nearly 7 lakh dwellings within 100 metres of the sea.The other casualty of climate change-induced changes on the coast is infrastructure, primarily ports. India has more than 200 ports and 95% of the country’s trade by volume and 70% by value are done through them. “Sea level rise, storm surges and waves are likely to induce major impacts on coastal transport hubs and networks, including transient or permanent flooding of seaports and connecting coastal roads and rail lines,” says a report by the United Nations Conference on Trade and Development.Aside from the damage to tourism and industry, rising sea levels could mean increased salinity in freshwater resources and challenges in farming as low-lying coastal lands are inundated by salt water. Around 2 lakh farmers in Bangladesh are expected to move inland because of this and many are switching to aquaculture because of the flooding from the sea, according to a study by Ohio State University In India, climate change could result in a 10% drop in yields of irrigated paddy in the majority of coastal districts by 2030, and a 15-50% decline in yields of irrigated maize, according to a 2011 study by the Indian Agricultural Research Institute and the CGIAR Research Program on Climate Change, Agriculture and Food Security. There are salt-tolerant varieties of paddy and maize being developed in response to this.It is clear that local administrations in coastal cities and towns will have to prepare themselves for the effects of climate change. Putting up barriers to fight rising sea levels is expensive, says Ravindranath.“The only option is to grow mangroves all along the east and west coasts.” India has had a National Action Plan on Climate Change since 2009 and states have since released their own plans.“But these plans do not have legal backing unlike disaster management plans,” says Anil Gupta, associate professor at the National Institute of Disaster Management.It is becoming increasingly hard to turn a blind eye to the adverse effects of climate change as they are no longer something only the next generation will have to contend with.While India has to leave no stone unturned in meeting its target on carbon emissions, governments — at the Centre, state and local levels — have to make sure the most vulnerable parts on the coast are resilient enough to withstand the consequences of climate change.