Extreme Heat Waves and Mitigation | 18 Apr 2023

For last few years, heat wave during the summer season is increasingly affecting morbidity

and mortality in the country. Heat waves are a growing concern for disaster management in India, causing widespread health and environmental impact.

Extreme weather events have become more frequent globally, requiring communities to understand and cope with heat waves.

From the view of hazard mitigation, rising number of heat wave related deaths is expected to serve as danger signal and corroborate the need to develop innovative methods to control summer-time losses.

What is Heat Wave?

• Heat wave as a hazard causing disaster scenario, is little more than the physical phenomenon of high heat conditions and is characterized as a complex of hydro-climatic risks coupled with social, occupational and public health risks.
• Definition:
  • As such there is no universal definition for heat wave.
  • It is generally defined as a prolonged period of excessive heat.
• Indian Meteorological Department (IMD) Criteria:
  • 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.
  • If the normal maximum temperature of a station is less than or equal to 40°C, then an increase of 5°C to 6°C from the normal temperature is considered to be heat wave condition.
    • Further, an increase of 7°C or more from the normal temperature is considered a severe heat wave condition.
  • If the normal maximum temperature of a station is more than 40°C, then an increase of 4°C to 5°C from the normal temperature is considered to be heat wave condition. Further, an increase of 6°C or more is considered a severe heat wave condition.
    • Additionally, if the actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, a heat wave is declared.

To What Extent Heat Wave is the Problem?

• Heat Stress:
  • 350 million Indians exposed to strong heat stress between April and May 2022
• Temperature Trends:
  • Summer temperatures have risen by 0.5-0.9°C across districts in Punjab, Haryana, Uttar Pradesh, Bihar, and Rajasthan between 1990 and 2019.
  • 54% of India's districts have seen a similar rise in winter temperatures.
  • Maximum temperature is expected to rise by 2-3.5°C in 100 districts and by 1.5-2°C in around 455 districts between 2021 and 2050.
• Urban Heat Island Effect:
  • Rising temperatures lead to urban heat island effect with temperatures 4-12°C higher than rural area.
• Climate change exacerbates local weather patterns, leading to weather variability and losses in agriculture.

What are the Causes?

• Sparse Pre-Monsoon Season Showers:
  • Less moisture in many areas, leaving large parts of India arid and dry.
  • The sudden end of pre-monsoon rain showers, an uncommon trend in India, has contributed to the heat waves.
• El Nino Effect:
  • El Nino often increases temperatures in Asia, combined with the weather pattern to create record high temperatures.
  • Trade winds coming from South America normally blow westward towards Asia during Southwest Monsoon and warming of the Pacific Ocean results in weakening of these winds.
    • Therefore, moisture and heat content get limited and results in reduction and uneven distribution of rainfall across the Indian sub-continent.

What are the Impacts of Heat Waves?

• Health Impacts:
  • Heat rash:
    • Also known as sunburn phenomenon with pinkish skin resulting in burning of skin and pain sensation.
  • Heat syncope:
    • Giddiness, vertigo headache and sudden onset drowsiness/unconsciousness.
  • Heat Cramps:
    • Edema (swelling) and Syncope (Fainting) are generally accompanied by fevers below 39°C i.e.,102°F.
  • Heat Exhaustion:
    • Fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.
  • Heat Stroke:
    • Body temperatures of 40*C i.e., 104*F or more along with delirium, seizures or coma. This is a potentially fatal condition.
• Impact on Labor and Productivity:
  • Heat exposure leads to a loss of 162 hours per year for laborers doing heavy work, impacting productivity.
  • About 50% of India's workforce is estimated to be exposed to heat during their working hours, including marginal farmers, construction workers, and street vendors.
• Impact on Agriculture Sector: Crop yields suffer when temperatures exceed the ideal range.
  • Farmers in Haryana, Punjab and Uttar Pradesh have reported losses in their wheat crop in the past rabi season.
  • Livestock is also vulnerable to heatwaves.
• Food Insecurity:
  • The concurrence of heat and drought events are causing crop production losses and tree mortality.
  • The risks to health and food production will be made more severe from the sudden food production losses exacerbated by heat-induced labour productivity losses.
  • These interacting impacts will increase food prices, reduce household incomes, and lead to malnutrition and climate-related deaths, especially in tropical regions.
• Impact on Energy Demand:
  • Average Daily peak demand rises due to increased heat.

What Should be Mitigating Strategies?

• Urban Greening:
  • Greener and more permeable urban surfaces can help reduce urban heat.
  • Development plans for Tier 2 and Tier 3 cities can set up a mandate to increase the density and area of urban forests.
  • Natural landscapes in urban areas, such as trees, parks, and vegetation, can help in cooling.
• Infrastructure:
  • Greater usage of permeable materials in civic infrastructure and residential construction can reduce the urban heat island effect.
  • Encouraging cleaner cooking fuels such as Biogas, Compressed Natural Gas, liquified Petroleum Gas will reduce indoor air pollution and urban heat.
  • Improving public transportation and reducing personal vehicle usage can help in reducing extreme heat waves.
• Waste Management:
  • Reducing the size of landfills, waste segregation, and solid waste management at the source can reduce methane production and fires that exacerbate urban heat.
• Policies and Guidelines:
  • Policies and guidelines on weather variability and urban heat management are needed at various levels.
  • Expanding wetlands and restoring ponds and lakes may also help.
• Building Design:
  • Promoting the use of green roofs and cool roofs in buildings, increasing ventilation, and setting up green spaces.
  • Passive cooling techniques such as natural ventilation, shading, and thermal insulation can significantly reduce indoor temperatures and energy consumption.
  • High-albedo roofs and pavements in the buildings.
• Renewable Energy:
  • Promoting the use of renewable energy sources such as solar and wind energy for cooling and electricity needs.
• Public Awareness:
  • Educating the public about the risks of heatwaves, how to stay cool, and the importance of reducing carbon footprint.
• Agricultural Adaptation:
  • Supporting farmers with resilient farming practices that take into account the risks of heatwaves, droughts, and water scarcity.
  • Crop diversification, Agroforestry, mulching, crop rotation, and cover cropping, drip irrigation and sprinkler systems can be helpful.
• Disaster Management:
  • Developing emergency response plans for heatwaves, including providing cool shelters and adequate medical facilities.
  • In the short-term:
    • It is essential to establish an effective early warning system that can provide timely and accurate information to people at risk.
    • This system should be integrated with public health services and local governments and should be able to mobilize resources quickly in response to a heat wave.
  • In the long-term:
    • Structural infrastructure measures are required to help Indians adapt to extreme heat.
• Green Transport:
  • Encouraging the use of public transport and bicycles to reduce vehicle emissions and traffic congestion.
  • Bicycles, Electric Vehicles etc. can be helpful.