Climate change: Mumbai at high flood risk; Heat, humidity to make India uninhabitable if emissions not cut

Mumbai is at a high risk of severe flooding and rise in sea level, the latest Intergovernmental Panel on Climate Change (IPCC) report has warned. The IPCC on Monday released the second part of its sixth assessment report, which deals with the impact of climate change, vulnerabilities and risks, and adaptation measures. The panel has also released regional assessments for the first time, focussing on mega-cities. The IPCC report notes that India is among the most vulnerable countries in terms of the population that can be affected by a sea-level rise.

Hot extremes, including heatwaves, have intensified in the cities, the IPCC report said. The cities also have aggravated air pollution events and limited functioning of key infrastructure.

The report added that the impacts observed were concentrated among the socially and economically marginalised urban residents. Extreme and slow-onset events have compromised infrastructure, such as transportation, sanitation, water, and energy systems, resulting in economic losses, service disruptions, and impacts on well- being.

If emissions are not eliminated rapidly, heat and humidity will create conditions beyond the threshold of human tolerance. The report warned that India is among the places likely to experience these conditions.

Prof Anjal Prakash, a lead author on the chapter on cities, key infrastructure, and settlements, told The Indian Express that urban India was at greater risk with its population projected at 877 million by 2050, nearly doubling from 480 million in 2020. Urbanisation in India is at 35%, which is likely to go up to 40% in 15 years. Mega-cities are growing faster, while smaller centres are rapidly growing, she said.

Prof Prakash said the population concentration in these cities made these settlements vulnerable to climate change.

The IPCC report also refers to wet-bulb temperatures, a measure combining heat and humidity. A wet-bulb temperature of 31°C is extremely dangerous for humans, while 35°C is unsurvivable for more than six hours, even for healthy and fit adults.

Wet-bulb temperatures rarely exceed 31°C in India, with most parts experiencing maximum wet-bulb temperatures in the 25-30°C range, the IPCC report said. It also noted that if emissions are cut only by the currently promised levels, several parts of coastal and northern India would reach wet-bulb temperatures of over 31°C towards the century’s end.

If emissions continue to rise, wet-bulb temperatures will exceed or approach the unsurvivable threshold over much of India, with the majority breaching the 31°C wet-bulb temperature mark.

The IPCC report has also warned that Ahmedabad would turn into a serious case of urban heat island. It sees several cities, such as Chennai, Patna, Bhubaneshwar, and Lucknow, approaching dangerous heat and humidity levels.