Mumbai is second on global list of coastal cities at risk

Future climate projections show that among 136 coastal cities across the world, Mumbai is second-most at risk to climate-induced sea level rise and extreme weather

Future climate projections show that among 136 coastal cities across the world, Mumbai is second-most at risk to climate-induced sea level rise and extreme weather events. Guangzhou in China tops the list and Kolkata was identified as seventh-most at risk.

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A study of the economic impact of inundation was carried out by researchers from Basque Centre for Climate Change (BC3) in Spain, and Oxford University, London School of Economics, and Liverpool Oceanographic Centre in the United Kingdom. They assessed projected damages and suggested graded solutions for worst-case scenarios in their report. Titled “Comparing urban coastal flood risk in 136 cities under two alternative sea-level projections”, the study was recently published in the international peer-reviewed journal Ocean and Coastal Management.

“We found that Guangzhou followed by Mumbai and New Orleans (in Louisiana, USA) face the highest risks in both scenarios among 136 global coastal cities,” said Elisa Sainz de Murieta, corresponding author from BC3, in an e-mail interview to Hindustan Times. She stressed the importance of identifying measures that are appropriate to the specific needs of each city. “It is essential to avoid damages to households and main infrastructures, but it is also important to understand that risk will increase with time,” said Sainz de Murieta.

Annual average damages to property and livelihood in Mumbai could exceed US $100 billion in 2050, in the absence of strong mitigation and adaptation efforts due to increasing risks. This may further rise to $328 billion by 2070 and $734 billion by 2100. These projections were made under a standard assessment scenario of RCP8.5 and 1m global sea rise, said the study. RCP, representative concentration pathway, is a measure of greenhouse gas concentration and RCP8.5 imagines a worst-case scenario in the absence of climate-change policies.

Sainz de Murieta clarified that the scenarios they’ve studied are “pessimistic”. “A scenario compatible with the Paris Agreement would translate in a global sea-level rise of 26-55 cm by 2100. RCP8.5 is a pessimistic scenario that could reach 4.3 degree Celsius temperature increase as compared to the pre-industrial era,” she said, adding that the second scenario considers a more dramatic situation based on larger contributions to global climate change. “These are not the most likely scenarios, but show how climate change could impact coastal cities if mitigation commitments are not ambitious enough to comply with targets,” said Sainz de Murieta.

The report comes at a time when Nisarga, classified as a severe cyclone, struck the Maharashtra coast as one of the strongest cyclones since 1891. Though its impact on the country’s financial capital was limited, it brought to the fore the need for Mumbai to set up measures to tackle such events in the future.

Analysis of a second scenario with increased risk predicted damages could be 2.8 times more than the current estimates for Mumbai, highlighting annual average losses of US $245 billion by 2050, US$636 billion by 2070, and US $1,355 by 2100, with larger contribution of faster-melting of ice sheets. “Our intent was to highlight that often only likely damages are considered and we ignore those risks that have a small probability. However, as the Covid-19 situation has shown, having a small probability does not mean it cannot happen. We argue that this information could be used, for example, for stress testing measures or infrastructures, but it should be taken as a warning and should not be ignored,” said Sainz de Murieta.

The paper suggests authorities analyse the impact of disaster projections and build adaptive measures that keep in mind worst-case scenarios. The other option was providing co-benefits, said Sainz de Murieta. “For example, mangroves protection, which in addition to coastal protection offer additional services like supporting livelihoods and improving biodiversity. Preventive measures, such as early warning systems and social protection policies are also cost-effective options,” she said.

City-based independent experts said increasing frequency of storms, cyclones and extreme weather events are all connected directly and indirectly to climate change, and therefore likely to increase. “All these cumulatively have severe impact on humans and land. After all, all that happens on land is a direct attribute of what happens in oceans since the latter governs most of the climate and not the land,” said marine biologist Deepak Apte.

Environmentalists said Mumbai’s coastal road, Navi Mumbai International Airport, and the underground Metro-3 project were examples of projects that were planned without considering the impact of the rising sea level. “In addition to curbing mangrove destruction, such unplanned projects make us more vulnerable to such disasters,” said environmentalist Debi Goenka.