No Respite After Dark: Why Are Our Cities Unable to Cool Down at Night?

How does extreme heat during the night impact your health? What does modern urban planning have to do with it?

This year, Northern India experienced one of the most brutal summers in recent history with temperatures soaring beyond 50^o C, and an unprecedented rise in heat-related deaths.

So much so that several government hospitals in the capital decided to open dedicated heat stroke units to deal with the influx of patients with severe heat related illnesses.

While the sun is punishing, things aren't much better at night. Delhi and other parts of north India have been recording nighttime temperatures of 35o C and higher.

"It's so hot at night that fans are completely useless. It feels like they're throwing flames. You can't even bathe because the water in the pipelines is so hot," Muhammad Shafi, a street vendor in South West Delhi said, speaking to FIT last week.

How does extreme heat during the night impact your health? Does poor urban planning have anything to do with it? FIT explains.

Why Are Nights Getting Hotter?

According to a recent study published in Geophysical Research Letters, the diurnal temperature range or the difference between daily maximum and minimum temperature has declined in recent decades. This means that night-time temperatures have been rising faster than daytime temperatures.

Speaking to FIT, Dr Anjal Prakash, Research Director and Adjunct Associate Professor, Bharti Institute of Public Policy, Indian School of Business (ISB), Hyderabad India, says that there are two major causes for this.

First, he says, there is the climate change, greenhouse gases and global warming aspect of it.

"We know that we have already breached the 1.5o C threshold last year when the global average temperatures was 1.8°C above pre-industrial levels. That has an impact on many ecosystems."

Dr Anjal Prakash

The question then arises, are we adapting to these harsh conditions that are becoming regular features year after year?

This is where the second aspect comes in, says Dr Prakash. "Urban planning in India, or the lack thereof, has significantly contributed to making them (the cities) hotter than they need to be. It may be 40 degrees but it feels like 50 degrees or higher." This phenomenon is known as urban heat islands.

According to experts, urbanised areas tend to experience higher temperatures than outlying areas because of the increase in concretisation, construction, and high-rise buildings.

Prof Raghu Murtugudde, an Earth System Scientist aggrees. He tells FIT, "In rural areas, you have a lot of space between buildings and land isn't as paved as in the cities, its mostly soil which helps the temperature in rural areas remain slightly cooler than in the cities."

"Because modern buildings in cities are tall and there's very little space between them, the heat, which should dissipate after sunset, just bounces between the buildings and gets trapped."

Prof Raghu Murtugudde

Moreover, adds Dr Prakash, the tall glass buildings preferred in the west for modern offices are not climate-friendly in India. "They absorb and trap heat easily and it takes too much energy to cool these buildings. Then we are forced to use more powerful ACs running for longer which then contributes to increasing the outside temperature even more," he explains.

"We are aping the western world without taking our wheather patterns into considerations, and without consideration for how its contributing to the climate crisis."

Dr Anjal Prakash

How Do Hot Nights Impact Your Health?

Extreme heat in itself puts a massive strain on one's body. There is the risk of dehydration, but also more severe outcomes of overheating like heatstroke.

Severe heat stress has been linked to an increased risk of both cardiovascular issues and stroke, and it's a serious concern. In India, between the months of March and June, over 100 people have died of confirmed or suspected heat stroke.

To make matters worse, studies have shown higher nighttime temperatures further heighten the health risks.

Nighttime heat makes it especially harder to fall asleep, and lack of sleep "is responsible for a lot of health issues like stress, irritability, inability to focus, cardiovascular diseases, and even diabetes," says Prof Murtugudde. The elderly, women, and residents of lower-income countries are impacted most.

According to experts, a disturbed and interrupted sleep reduces the amount of time your body spends in REM (rapid eye movement) mode – the deep stage of sleep when the body repairs itself at night.

Moreover, a study involving over 20,000 participants that was published in Sleep Medicine in 2021 found that disturbed sleep is linked to higher psychological distress.

Having said all of this, making the connection between extreme heat and a specific health condition can be tricky.

"Heat-related morbidity and mortality is a very understudied science in India at the moment," says Dr Prakash. "We dont have enough scientific evidence to establish the link yet."

"We know from anecdotal interactions that heat does impact mobility and increases risk of cardivascular diseases, but there usually isn't a direct causal link, rather a combination of factors together. This is why it's very difficult to establish even deaths to heat stroke and the heat waves."

Dr Anjal Prakash

"This requires a significant sample size, and the medical fraternity has to keep meticulous records and study this," he adds.

Can the Damage Be Undone?

Alright, we ignored the warning signs and now the dreaded global warning has caught up to us, moreover, poor urban planning is making things worse. Is there a way to undo the damage? Are there measures we can take now to bring down the temperatures of our cities gradually and ensure better cooling, particularly at night? In short, is there still hope?

According to the experts FIT spoke to, yes there is.

Some policy changes at the systemic level that can help are,

• Protecting existing forest areas and taking steps to actively improve the green cover.

• Protecting and conserve waterbodies in and around cities.

• We need heat action plans and guidelines that incentivise climate-friendly construction.

• Incorporating more open spaces in urban town and city plans.

• Providing night shelters for those who dont have the means to install cooling systems like in winters.

According to Prof Murtugudde, on a personal level one can paint their roofs with white paint or lime that reflects sunlight instead of trapping it like some other paints do.

Ultimately, it comes down to quick action. "We talk about this every year, but nothing has really been done. We also have the responsibility to keep raising the issue," says Dr Prakash.