Warm, sleepless nights in a concrete jungle

As Delhiites await some respite from the intense heatwave, when the mercury surpassed 35 degrees Celsius even at night, discussions on the growing number of urban heat islands in the Capital have once again come to the fore.

“The combination of high day and night-time temperatures is dangerous as it seriously impacts the blood circulation and other bodily functions of people, especially the elderly,” said Dileep Mavalankar, Director, Indian Institute of Public Health, Gandhinagar.

Dr. Mavalankar, who helped implement Ahmedabad’s heat action plan, said unlike what is usually perceived, heatwave deaths are not common in labourers or women working in scorching heat but in the elderly age group due to non-exertional heatstrokes.

Explaining the condition, he said, “As the house becomes hot and is unable to cool down by midnight, it starts acting as a heat trap. In such a situation, the body gets heated overall and the heart starts pumping more blood to fight dehydration if adequate water intake is not maintained. If one’s heart is already weak, it may fail and the person may die due to cardiac failure induced due to heatwaves.”

Heat-related deaths

Data on ‘Accidental Deaths & Suicides in India’ released by the National Crime Records Bureau show over the years heatstrokes have become the second leading cause of death from a natural force in India, with 11,555 people being killed from 2011 to 2020 due to the condition.

In 2020, Ahmedabad and Hyderabad, which have heatwave action plans that track every heat-related death, reported heatstroke to be the reason for the maximum – 50% – deaths due to natural forces. Delhi reported no such death, according to the data. The Delhi government did not provide a comment on whether it tracks heat-related deaths.

Most cases go unreported as the ambiguity of symptoms makes it difficult to accurately capture mortality rates, say experts, therefore making it difficult to correlate the effect of heat islands with people’s health.

Taking insights from South Asia and India’s first heat action plan that came up in Ahmedabad in 2013, the Centre is currently working with 23 heatwave-prone States and over 130 cities, including Delhi, to implement a similar action plan.

“There was a draft heat action plan, which was prepared three-four years ago, but it never went beyond that,” a Delhi government official said.

Growing heat island effect

An image captured by NASA on May 5 showed how night-time temperatures in Delhi and adjoining villages were above 35 degrees Celsius, peaking at about 39 degrees Celsius, while the rural fields nearby had cooled to around 15 degrees Celsius by then.

The World Weather Attribution network, which analysed the heat patterns in India from March-April, found that the probability of long-duration heatwaves had increased by 30 times due to human-induced climate changes.

“One way of looking at the cause of urban heat islands is global warming but the other side of the coin is that these heat islands are linked to micro-climatic changes, which occur when we start disrupting our landscapes,” said Abinash Mohanty, Programme Lead, Risks and Adaptation, Council on Energy, Environment and Water.

“Over 60% of Delhi’s landscapes are disrupted, signalling alteration or encroachment of tree cover, forest cover, wetlands and natural ecosystems,” Mr. Mohanty said.

Mitigative approach

One way of countering the growing impact of urban heat islands is ‘green infrastructure’ that includes cool roofs or painting house roofs in a light colour to reflect heat and using sustainable cooling mechanisms. Promoting urban forestry and green transport can also help cut down heat emissions.

“Climate-proofing of infrastructure applies not only to posh localities but also low-cost housing areas. We already have government modules, which lay out how affordable housing can be climate-proofed,” Mr. Mohanty added.

Experts point out that the action plans on extreme weather events need to assess hazard risks and vulnerability at a hyperlocal level, the absence of which has made us experience floods in one part of the country and heatwaves in another.

Launched in 2019, the Centre’s ‘Cooling Action Plan’ aims to minimise energy consumption for cooling appliances in residential and commercial areas, speaking about which, Mr. Mohanty said, “The action plan has granular information to address extreme heat conditions, but a gap exists in implementation as the stated actions aren’t hyperlocal.”

Heat traps 

From Bhalswa landfill to Mundka industrial area, Delhi has witnessed massive fire incidents over the last three months. Industrial areas in the Capital like Najafgarh and Mungeshpur have been acting as heat traps, with the mercury soaring to over 49 degrees Celsius at these places in May.

According to Mr. Mohanty, industries need to improvise their emission pathways and minimize heat emission through thermal innovations. As for Delhi’s huge landfills, nature-friendly alternatives could halt temperature rise to a large extent.

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Printable version | Jul 16, 2022 6:25:17 am |