Number of warm nights in Indian cities leapfrogged 32% during last decade due to climate change: Global report

Sub: Geography

Sec: Climatology

Increase in Warm Nights in India Due to Climate Change:

Over the last decade, India has experienced a critical increase in warm nights with minimum temperatures due to rising climatic impacts.
Jalpaiguri in northern West Bengal, along with cities in Assam, is the most impacted.
A study covering around 300 Indian cities found a 32% increase in hot nights, averaging 718 nights from 2014-2023 where temperatures reached 25°C or above.
Without climate impact, this number would be significantly lower, around 543-175 nights.

What is a ‘warm night’?

A warm night is when the minimum temperature is 4.5 to 6.4°C above normal; a severe warm night exceeds this by more than 6.4°C. The day temperature must be 40°C or higher for these conditions.
Northwest India is experiencing a significant rain deficit and consistently high temperatures. Increased night temperatures are causing more heat stroke cases, as people find no respite from the heat.

Climate Change Impact:

Climate change has significantly influenced night-time temperatures above 25°C in India, especially in West Bengal and Assam.
Cities like Jalpaiguri, Guwahati, Silchar, Dibrugarh, and Siliguri experienced 80-86 additional hot nights annually due to climate change.
The urban heat island effect contributes to higher night-time temperatures due to the retention of heat by high-rise buildings and concrete.

What us Urban Heat Island effect?

Urban heat island may be defined as the local and temporary phenomenon in which certain pockets within a city are experiencing higher heat load than its surrounding area.
This rise of heat basically happens due to buildings and houses of cities made up of concrete where the heat is trapped and not able to dissipate easily.
Urban heat island is basically induced due to trapped heat between establishments made up of concrete.
The temperature variation can range between 3 to 5 degrees Celsius.

Regional and National Trends

The impact of climate change has added 50-80 hot nights annually in cities across several states including Kerala, Karnataka, Maharashtra, Tamil Nadu, Punjab, Jammu and Kashmir, Andhra Pradesh, West Bengal, and Assam.
Jalpaiguri had the highest number of unusually hot nights (868) during 2014-2023, followed by Guwahati, Silchar, Dibrugarh, and Siliguri.
Major cities like Chennai, Kolkata, Mumbai, and others experienced significant increases in hot nights.

Challenges and Observations

The increasing trend of hot nights poses challenges for sleep and health, particularly for vulnerable populations without adequate cooling mechanisms.
Scientists highlight that the trend is exacerbated by air pollution and urbanization, which trap heat and prevent cooling at night.
Recent records for night-time heat were broken in cities like Delhi and Alwar, with temperatures reaching unprecedented highs.
Experts emphasize the severe consequences for human health and the need for immediate action to mitigate these impacts.

Source: DTE