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Almost 40°C in March? Why sizzling heatwave caught Mumbai by surprise last week

This year's March maximum as yet slightly lower than for last year — 40.9 degrees Celsius — recorded on 28 March 2021. City's highest-ever March maximum recorded in 1956.

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Mumbai: The mercury soared in Mumbai last week. With two weeks left for March to end, the Maharashtra capital, and cities neighbouring it, saw maximum temperatures touching nearly 40 degrees Celsius — 39.6 degrees Celsius — around 15 March, resulting in severe heatwave conditions.

According to the India Meteorological Department (IMD), a severe heatwave is declared in a coastal station like Mumbai when the daytime maximum temperature is above 37 degrees Celsius, or when it is more than 6.5 degrees above normal temperatures for that time.

On average, a maximum day-time temperature of 33 degrees Celsius is considered normal for this time of the year. While that has been breached, according to IMD data, this year’s maximum is as yet slightly lower than the highest maximum temperature for March last year — 40.9 degrees Celsius — recorded on 28 March 2021. The highest-ever maximum temperature recorded in Mumbai in March so far has been 41.7 degrees, recorded on the same date in 1956.

This week, the maximum temperature has climbed down a bit — it was 37 degrees Celsius Thursday — but with the city showing a general trend of getting warmer in the past five decades, another heatwave may not be that distant.

Last week, the Brihanmumbai Municipal Corporation (BMC) came out with a climate action plan, which also listed a climate and air pollution risk and vulnerability assessment report for the city. The study was conducted by research organisation World Resources Institute India, in collaboration with the BMC.

According to the report, Mumbai has shown a warming trend over the past nearly five decades. Between 1973 and 2020, the average maximum temperature in Mumbai has increased by 0.25 degrees Celsius per decade, the report says.

An increase in frequency of warmer years has also been observed, with three out of the past five years recording higher-than-average temperatures. Since the mid-1990s, a transition from caution to extreme caution events has been observed, with over 200 days annually classified as extreme caution events.

If the maximum temperature rises over 35 degrees Celsius for a coastal city, it is considered a caution situation, whereas anything near 40 degrees Celsius is extreme caution.

During this period, a total of 10 heatwaves and two extreme heatwave events have occurred, the report says. While heatwaves were reported in 1977, 1981, 1985, 1989, 1995, 2005, 2009, 2013, 2014 and 2018, extreme heatwaves were observed in 2004 and 2011.

The report also analyses land surface temperature (LST) data, to identify heat islands in the city — areas where increased heat exposure is caused by land-use patterns, such as industrial and commercial, or because of poor vegetation cover, high exposure to heat-conductive or reflective building materials (such as metal roofs, glass and steel structures). In informal settlements with high habitation density and low vegetation cover, temperatures were observed to be 6-8 degrees higher than in neighbouring residential areas.

According to the report, by 2040, 60 per cent of the days in Mumbai annually will comprise high-heat days, when temperatures could exceed 32°C. This, along with high-humidity days, would increase heat exhaustion and result in a sudden spike in heat-related deaths and illnesses.

Also read: In last 20 years, death rate due to heatwaves increased by 62% in India, IMD study says

An urban crisis

Last week’s unexpected heatwave, so early in the year, left residents reeling.

The BMC issued a notification asking citizens to be hydrated at all times and also “avoid tea, coffee, soft drinks, high-protein and stale food”. It also suggested that people use a hat or an umbrella and a damp cloth on head, neck, face and limbs while working outdoors.

“If a person faints or falls ill, he/she should see a doctor immediately,” it stated. The BMC also suggested that if a person suffers from sun stroke, he or she should lie in a cool place under a shade.

For 56-year-old Shashikala Khadtare, the sudden heatwave meant dehydration and a rush to buy an air-conditioner. A healthcare worker with the Maharashtra government for the past 27 years, Khadtare’s work requires her to make door-to-door visits, to impart health education and knowledge to residents of the city’s Ghatkopar area. Work starts at 9 am and continues till 2 pm.

But last week, Khadtare was forced to take small breaks between work, as she felt unusually dehydrated.

“I used to feel the heat in April-May but this time it is only March and the heat has increased so much,” Khadtare told ThePrint. “My head spins in the heat so I have to sit in the shade, but then I sweat profusely. Even my blood pressure went down because of the dehydration.”

The unexpected heat also forced Khadtare, who lives in a one-room flat in Mumbai’s Mankhurd area, to make an early investment in an air-conditioner. “I was planning to buy one in May, but I was forced to get an AC this month on EMI as it is getting hotter everyday and we were finding it very difficult to sleep otherwise,” she said.

Areas more vulnerable than others

The vulnerability and risk assessment conducted for the BMC’s Mumbai Climate Action Plan (MCAP) also revealed the areas of Govandi and Mankhurd in M-East ward of BMC to be most susceptible to problems of urban heat.

According to the report, 40 per cent of the area’s nearly 10 lakh population is over-exposed to urban heat and a surface temperature of over 35 degrees Celsius.

“Because of industrialisation in that area and heightened construction activity, Mankhurd, Chembur, Govandi are seeing a spike in urban heat,” explained environmentalist Debi Goenka. The problem is heightened, he said, because the area has less vegetation owing to construction, leaving more land exposed to heating.

Nasimunissa Sheikh, who runs a food stall in Mankhurd, has been already feeling the impact of the early onset of summer this year. While the months of April and May were always difficult for the 45-year-old, who spends hours everyday in front of the tandoor and stove, “March was hardly unbearable before”.

“But last week was very hot. Every two hours, I had to take shower to cool down. Summer doesn’t come this early normally,” she said. Nasimunissa also complained of the lack of tree cover in the area which she said made the heat here worse than in many other parts of the city.

The hours spent in front of the fire cooking, amid last week’s intense heat, also resulted in her developing skin rashes on her hands and legs, for which she is currently undergoing treatment.

Mumbai climate action plan

Meanwhile, earlier this month, Mumbai announced detailed plans to zero out carbon emissions by 2050, a target that puts it two decades ahead of India’s national goal of zero emissions by 2070. The 2050 target makes Mumbai the first city in South Asia to set such a timeline.

The plan proposes exhaustive changes to the way the city manages energy, water, air, waste, green spaces and transport for citizens.

“We don’t have the luxury of time,” Maharashtra Environment Minister Aaditya Thackeray had said while unveiling the plan. “Across India, there is a certain sense of urgency everyone feels. The policies are actually opening the doors for such investments to come in,” he said.

According to the report, in 2019, Mumbai’s carbon emissions stood at 23.42 million tonnes.

The plan also proposes to increase the city’s vegetation cover and permeable surface (from where steam could evaporate) to cover 30-40 per cent of the city’s surface by 2030, to tackle flood- and heat-related disaster risks.

(Edited by Poulomi Banerjee)

Also read: South Pole warmer by 40°C, North Pole by 30°C. Simultaneous highs alarm scientists


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