When we talk about 'a tougher world', we are not talking about Trump or Iran war and even characters like Narendra Modi, his 'melody' or Rahul Gandhi and his 'mirchi lagi song' -- meaning Gaddar rhetoric in Rae Bareily.
According to a global study released in 2024, the number of hot nights has increased by around 32 per cent on average due to climatic impacts.
The study covered around 300 Indian cities with populations of over 100,000.
A 2020 climate assessment by the Ministry of Earth Sciences found that between 1986 and 2015, daytime temperatures rose more sharply than nighttime temperatures.
The warmest day of the year increased by about 0.63 degree Celsius, while the coldest night rose by 0.4 degree Celsius.
Welcome to the post-Climate Change world.
IMD classifies 'warm night' when the minimum temperature stays 4.5 to 6.4 degrees Celsius above normal after a day when the maximum temperature crosses 40 degrees Celsius. A 'severe warm night' is when the departure exceeds 6.4 degrees Celsius.
Missive is crystal clear -- Warmer nights during summers may be more dangerous than heatwaves during Day time.
"Urban Heat Island Effect":
More and more concrete roads, felling of tress, brick buildings, and asphalt absorb heat all day and slowly radiate it back out after dark.
The lack of green cover and shrinking water bodies in cities—coupled with the heat exhaust from air conditioners—prevents nighttime temperatures from dropping.
Moreover, increased atmospheric moisture prevents human sweat from evaporating effectively, and humid air retains more heat, making nights feel significantly warmer and stickier.
Rising night temperatures in India are worsening indoor heat exposure, increasing health risks for people living in poorly ventilated low-income housing.
"While most of the conversation about extreme heat during Indian summers is centred around peak daytime temperatures and the spells of heatwaves, it is slowly becoming evident that warmer nights could pose a greater health risk to human beings, particularly those living in low and middle-income housing units," writes Amitabh Sinha in 'Indian Express'.
Delhi is in the grip of an intense heatwave with daytime temperatures soaring to 44-46°C in many parts of the NCR. But what makes this summer particularly punishing is how the heat lingers long after the Sun goes down.
Meaning, evenings and nights offer little relief, turning homes into ovens and making sleep difficult for millions.
On May 19, maximum temperatures hit 45°C across several stations, while minimums stayed elevated around 28°C or higher.
Through Tuesday night, temperatures hovered around levels usually experienced during day hours.
Of course, both day and nighttime average temperatures are on the rise in India, but recent data suggest that nighttime temperatures could be increasing at a faster rate.
Indoor thermal exposure could be a bigger threat to public health than exposure to heat outdoors during the daytime.
A cooler evening and night allow the human body to recover from the heat experienced during the daytime.
But if nighttime temperatures also remain high, the body is unable to recoup, and exposure to heat becomes prolonged and sustained, without any relief.
People are confined in small spaces for several hours at a stretch. The situation gets aggravated inside houses without natural ventilation or access to air-conditioning.
A recent study by Climate Trends, a Delhi-based climate-focused research organisation, in 50 houses in Chennai, all medium and low-income residential units, showed that the occupants were frequently sleeping in temperatures in excess of 32° Celsius.
Sometimes, night-time temperatures even exceeded 35° Celsius, very similar to peak day-time temperatures in the city.
Rising night-time temperatures
India’s average temperature has increased by about 0.7° Celsius between 1901 and 2018.
Both day and night-time temperatures have increased during this time, but at different rates.
In the 30 years between 1986 and 2015, the temperature of the warmest day of the year increased by about 0.63° Celsius.
That of the coldest night increased by 0.4° Celsius.
This would suggest that the rise in daytime temperature was more pronounced than the nighttime temperatures, and that is true for this period.
But the situation changes in future projections. The same assessment said that the temperature of the warmest day of the year could rise by 4.7° Celsius by the end of this century.
Greenhouse Gas Emissions:
Carbon dioxide and other greenhouse gases act like a thickening blanket over the earth. While they allow the sun's shortwave radiation to enter during the day, they trap the longwave heat radiating from the earth's surface at night.
While the rapid rise in night-time temperatures is happening everywhere, it is more pronounced in urban spaces, mainly because of what is called the urban heat island effect.
The lack of adequate vegetation and green spaces, loss of water bodies and dense clustering of high-rise buildings amplify this effect.
There could be a difference of 4-6° Celsius or more in the nighttime temperatures of a city centre or a dense residential area of a city, and its outskirts.
Most of urban India goes to sleep in small houses that are poorly designed and lack natural ventilation. If these houses lack air-conditioners, there is little nighttime relief for the human body.
Sleep discomfort, restlessness, exhaustion, and lack of energy are direct results.
