Heat Waves

What are Heat Waves?

  • Heatwaves are prolonged periods of excessively high temperatures.
  • India Meteorological Department (IMD) defined heat waves in plains as temperature exceeding 45°C for three or more days and in hilly areas as temperature exceeding 40°C for three or more days .

Heat Waves are Classified as

  • Extreme Heat Waves: High temperature with low humidity .
    • Regions Affected:
      • Deserts and semi-arid regions
      • Inland plains and plateaus
      • Areas with dry continental climates
    Examples:
    • India: Northwest India (Rajasthan, Gujarat, Punjab, Haryana, Madhya Pradesh)
    • Middle East: Saudi Arabia, UAE, Iran, Iraq
  • Oppressive Heat Waves: High temperature with high humidity (more dangerous due to heat stress).
    • Regions Affected:
      • Coastal areas
      • Tropical and subtropical regions
      • River valleys and floodplains
      • Low-lying urban areas with poor ventilation
      • Examples:
    • India: Coastal states like Tamil Nadu, Kerala, Odisha, West Bengal, and Maharashtra (Mumbai)
    • Southeast Asia: Bangladesh, Thailand, Indonesia, and the Philippines

Research Findings

  • Research was conducted by IIT-Bombay and ETH Zurich using historical climate data (1951–2013) and future projections (2035–2100) and also examined impact on human mortality .
  • They examine the situation under two scenarios of global warming — a rise in global temperatures by 2 degrees C; and by 1.5 degrees C.
    • 1.5°C global temperature rise: Five-fold increase in oppressive heat waves by 2035–2065 & 2070–2100 .
    • 2°C global temperature rise: Eightfold increase in oppressive heat waves by end of the 21st century .
  • Heat Related Mortality:
    • Strongly linked to oppressive heat waves rather than extreme heatwaves.
    • A higher risk in densely populated regions .
    • Calls for urgent adaptation measures to prevent mass casualties.

Humidity – The amount of water vapor in the air, which impacts how hot a temperature feels.

Measures

  • Mitigation: Reducing greenhouse gas emissions to limit warming.
  • Adaptation:
    • Early warning systems.
    • Heat action plans.
    • Improved urban planning (green spaces, reflective surfaces).