‘Urban heat, Mumbai’s next invisible threat after air pollution’

Nov 17, 2023 07:30 AM IST

Mumbai faces urban heat threat as temperatures rise, leading to heat islands and health risks. Mitigation measures urgently needed.

Mumbai: Even as the BMC attempts to combat the destructive phenomenon of air pollution, another silent threat is shadowing the metropolis. According to the civic body’s Mumbai Climate Action Plan (MCAP), prepared by the World Resources Institute (WRI), the city will face “urban heat” if mitigation measures are not set in motion promptly.

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“We will have to not just reduce pollution but also take measures to control temperature at source,” said a senior civic official from the BMC’s environment department. “Heat reduction is a major concern and we also have to reduce greenhouse gas emissions. Our target is till 2030-50.”

According to MCAP, Mumbai has presented a warming trend over a period of 47 years (1973-2020) with an increase of 0.25 degrees Celsius per decade. Ten heat waves and two extreme heat wave events were observed in this period.

“Our analysis showed that Indian Meteorological Department data since 1973 showed a clear increase in temperature, which corresponded to global climate models and the Intergovernmental Panel on Climate Change (IPCC) report,” said architect and urban planner Lubaina Rangwala from WRI, who was involved in drafting MCAP. “The IPCC report shows an unmistakable global warming trend, in which countries like India are seeing a much higher impact.”

Rangwala said that in the second part of the analysis, the team observed surface temperature using satellite data, which clearly showed that certain areas in the city emitted more reflected heat. MCAP has calculated the heat value and earmarked these “heat islands” at various places such as Dharavi, Matunga, Hanuman Nagar in Vikhroli, Powai Hiranandani, Bhagat Singh Nagar and Jawahar Nagar in Goregaon, Girgaon and Marine Lines.

“The Mumbai airport area, for instance, is a clear heat island because there are no trees,” said Rangwala. “It is fully concrete as compared to Sanjay Gandhi National Park where you see a decline in temperature. So, these are two extremes of a spectrum.”

Extreme heat is also witnessed in slum settlements, which are densely packed and have metal roofs. “Many indoor activities also produce heat in slums due to the lack of ventilation,” said Rangwala. “So these are indubitably heat islands as compared to other better ventilated areas of the city.”

According to the National Oceanic and Atmospheric Administration and Climate Lab Projections, by 2040, 60 percent of the year will comprise high heat days (temperatures exceeding 32 degrees C) in Mumbai. This, along with high humidity days, will increase heat exhaustion and result in a sudden spike in heat-related deaths and illnesses.

The solution, said Rangwala, is “heat action plans” for areas where exposure is projected to be higher and creation of “cooling shelters”. “In Ahmedabad, the authorities have been working on a heat action plan because for the last five to seven years, their temperatures have been routinely reaching 50 degrees C,” she said. “So they had to actively look at heat as a disaster just like we in Mumbai look at flooding as a disaster.”

In March 2022, two days after the first MCAP was introduced, there was a heat wave alert for the whole of the western coast, and Mumbai for the first time saw the BMC put out a heat warning. “This year, there were some warnings, but it will get worse,” said Rangwala. “It is an invisible risk. We will not realise when our body has reached the threshold of collapse, and if at that point there is no immediate medical care, one can even die. Outdoor workers such as construction and other labourers, rickshaw drivers and traffic police will be the most impacted.”

Commenting on remedial measures, Rangwala said the authorities needed to start active tree planting and creating shade in residential areas. “In the disaster management section, there are heat action plans and in the building sections there are recommendations on thermal cooling for people who do not have private ACs,” she said. “Solar-powered thermal cooling within the building and reflective materials on building facades with ‘thermal comfort’ should become a public health right which municipal corporations should engage with. If these adaption measures are not taken seriously, heat mitigation goals will not be met.”

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