Why in news?

The Tamil Nadu government recently declared a heatwave as a State-specific disaster, enabling relief measures for those affected and compensation for families of heat-related casualties.

Interim actions to manage the heat will also be implemented, with funds allocated from the State Disaster Response Fund.

What’s in today’s article?

• Rising Frequency of Heatwaves in India
• Heatwaves
• Wet Bulb Temperature and Heat Stress
• Recommended Government Actions

Rising Frequency of Heatwaves in India

• The World Meteorological Organization declared 2023 as the hottest year on record, with rising heatwave frequency attributed to anthropogenic climate change, as noted in the IPCC’s Sixth Assessment Report.
• In India, heatwaves have intensified, with significant health impacts documented. A study in Environment International highlighted frequent and severe heatwaves in recent decades, such as:
  • 1998: Severe two-week heatwave, the worst in 50 years.
  • 1999: Unprecedented April heat, with temperatures over 40°C for more than 14 days.
  • 2003: Heatwave causing over 3,000 deaths in Andhra Pradesh.
  • 2010: Ahmedabad heatwave led to around 1,300 deaths.
  • 2016, 2018, 2019, and 2023: Extreme heatwaves across India.
• In May 2024, a severe heatwave struck, with Churu, Rajasthan, reaching 50.5°C, the highest in eight years.
• The heatwave resulted in 219 deaths and over 25,000 cases of heatstroke, impacting people across the plains and hills.

Heat waves

• A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature.
  • In India, Heat waves typically occur from March to June, and in some rare cases, even extend till July.
  • On an average, five-six heat wave events occur every year over the northern parts of the country.
  • Heat wave is considered if maximum temperature of a station reaches at least 40°C or more for Plains and at least 30°C or more for Hilly regions.
    • Based on Departure from Normal: Heat Wave if Departure from normal is 4.50°C to 6.40°C; Severe Heat Wave: Departure from normal is >6.40°C
    • Based on Actual Maximum Temperature: Heat Wave if actual maximum temperature ≥ 45°C; Severe Heat Wave: When actual maximum temperature ≥47°C
• Health Impacts of Extreme Heat
  • Rapid rises in heat gain compromises the body’s ability to regulate temperature.
  • It can result in a cascade of illnesses, including heat cramps, heat exhaustion, heatstroke, and hyperthermia.
  • Prolonged exposure to extreme heat can lead to conditions from heat exhaustion to heat stroke and exacerbates issues like renal, cardiovascular, and pulmonary diseases.
  • Vulnerable populations—such as children, seniors, pregnant women, and outdoor workers—face higher risks. Extreme heat also impacts early childhood development, affecting learning, sleep, and mental health.

Wet Bulb Temperature and Heat Stress

• Wet bulb temperature is the lowest temperature achievable by evaporative cooling, such as sweating, and it measures the combined effects of heat and humidity.
• Beyond this threshold, the body can no longer cool itself, leading to heat stroke or death.
• This is particularly concerning for humid regions like India, with its extensive coastlines.
• Research indicates that a wet bulb temperature exceeding 35°C for prolonged periods poses a universal heat stress limit, making heat dissipation impossible and inducing hyperthermia.

Recommended Government Actions

• Equip health centers and hospitals with essential resources like ORS and medications.
• Offer water and shelters for those working outdoors.
• Adjust work hours to minimize outdoor exposure during peak heat times.
• Long-term goals include addressing climate change causes and improving infrastructure to reduce vulnerability, especially in low-income communities.