Three new heatwave hotspots in India put large population at immediate health risk

Three new heatwave hotspots in India put large population at immediate health risk

Subject: Environment

Context:  A team of researchers led by Prof. R.K. Mall and including Saumya Singh and Nidhi Singh from the Department of Science & Technology, Govt. of India-Mahamana Centre of Excellence in Climate Change Research (MCECCR) at Banaras Hindu University studied the change in spatial and temporal trends in Heatwaves (HW) and Severe heatwaves (SHW) over the past seven decades in different meteorological subdivisions of India.

Highlights of the study

• New hotspots of intense heatwave events over the past half-century have emerged
• There is an increase in deadly Indian heat waves in recent years.
• These hotspots are in the North-Western, Central, and further to south-central region of India.
• The study also highlights the need for developing effective heat action plans in the three heatwave hotspot regions with a focus on different vulnerabilities among the inhabitants.
• The study showed a shift in the Spatio-temporal trend of HW events from the eastern region of Gangetic West Bengal and Bihar to North-Western, Central and further to south-central region of India.
• The research also observed an alarming southward expansion and a spatial surge in SHW events in the last few decades that may put a greater population at additional risk of heat stress in a region already characterized by low Diurnal temperature range (DTR), or the difference between the maximum and minimum temperatures within one day and high humidity.
• Importantly, the HW/SHW events were found to be positively correlated with mortality in Odisha and Andhra Pradesh, highlighting that human health is highly susceptible to severe heatwave disasters.

Concept:

About heat wave

• A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India.
• Heat Waves typically occur between March and June, and in some rare cases even extend till July.
• Urban heat island effects, deforestation, global warming leading to higher daily peak temperature etc. are major causes of heat waves.
• The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, dehydration, heat cramps, heat exhaustion and/or heat stroke and sometimes resulting in death.
• Children, the elderly and those with pre-existing morbidities are particularly vulnerable.

IMD defines Heat Waves as:

1. Heat Wave need not be considered till maximum temperature of a station reaches at least 40°C for Plains and at least 30°C for Hilly regions
2. When normal maximum temperature of a station is less than or equal to 40°C Heat Wave Departure from normal is 5°C to 6°C Severe Heat Wave Departure from normal is 7°C or more
3. When normal maximum temperature of a station is more than 40°C Heat Wave Departure from normal is 4°C to 5°C Severe Heat Wave Departure from normal is 6°C or more
4. When actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heat waves should be declared.