HEAT ISLAND

HEAT ISLAND

An Urban Heat Island (UHI) is an urban or industrial area that experiences significantly higher temperatures compared to its surrounding rural areas, mainly due to anthropogenic activities.

• Example: Delhi’s near-surface temperature has increased by 1.02°C due to urban land use expansion from the 1970s to the 2010s.

Causes of Urban Heat Islands (UHI)

1. Heat-Trapping Concrete and Asphalt: These materials have low albedo, meaning they reflect less sunlight and absorb more heat. Urbanization replaces natural vegetation, reducing evaporation and cooling.
2. Close Construction: Dense construction of houses, shops, and industrial buildings traps heat. Insulating materials in buildings keep heat inside, raising surrounding temperatures.
3. Urban Haze: Pollution in the air acts like a greenhouse layer, preventing outgoing heat from escaping.
4. Vertical Infrastructure: Tall buildings offer a larger surface area for heat absorption.
5. High Vehicle Density: Vehicles release heat from their engines, contributing to higher temperatures.
6. GHG Effect: Greenhouse gases (GHGs) such as CO2, aerosols, and particulates absorb outgoing infrared radiation, trapping heat.
7. High Power Usage: Air conditioners and other appliances release heat into the atmosphere, further warming the urban environment.
8. Bad Monsoons: Urban areas with less vegetation and poor water retention cause reduced evaporation, affecting local weather patterns.
9. Lack of Trees and Green Areas: Fewer trees and green spaces result in less evapotranspiration and CO2 absorption, reducing natural cooling mechanisms.
10. Urban Heat Islands at Night: Cities tend to retain heat at night due to dense construction and pollution, unlike rural areas which cool down faster.

Impact of UHI

1. Energy Costs:
   • Increased temperatures raise the demand for air conditioning, which in turn increases energy consumption.
   • Higher energy use contributes to climate change through increased greenhouse gas emissions.
2. On Ecology:
   • UHIs encourage the colonization of species that thrive in warm environments, such as reptiles and insects.
   • These species are referred to as ectotherms, and they often invade urban environments from rural areas.
3. On Air Quality:
   • Urban pollution levels rise with UHI, as vehicle exhaust and industrial emissions contribute to higher levels of particulate matter in the air.
4. Poor Water Quality:
   • Warm water from urban areas flows into nearby streams and rivers, stressing aquatic species adapted to cooler temperatures.

Impact of UHI on Human and Animal Health

• Health Issues: The UHI effect can lead to heat cramps, sleep deprivation, and increased mortality rates due to extreme heat exposure.
• Heatwaves: Urban areas tend to experience more frequent and intense heatwaves, exacerbating the negative health impacts on both humans and animals.
• Meteorological Effects: The UHI effect can also alter local weather patterns, including wind direction, cloud formation, humidity, and precipitation.

Measures Required to Combat UHI

1. Modifying Heat-Generating Activities: Promote public transportation, electric vehicles, and the use of clean fuels to reduce heat generation.
2. Use Light Asphalt: Using lighter-colored materials in road construction and roofing to absorb less heat.
3. Cool Pavements and Roofs: Design streets and rooftops to reflect more sunlight, reducing heat absorption.
4. Green Roofing: Cover rooftops with vegetation to reduce temperatures and energy demand for air conditioning.
5. Decentralization of Development: Develop green cities, such as Amaravati, with a focus on sustainable development and reducing UHI.
6. Increase Vegetation Cover: Expand green belts and reclaim wastelands to promote natural cooling through vegetation.
7. Open Architecture Planning: Design urban areas to facilitate natural wind flow and minimize heat retention.

Measures Already Taken

1. Cool Roof Programs: Indian cities have implemented programs that lighten roof colors to reflect more heat.
2. Cool Pavement Programs: Aimed at reducing heat absorption at the street level by using reflective materials.
3. National Mission on Sustainable Habitat: Focuses on shifting towards sustainable construction materials and technologies that absorb less heat.
   • Example: The Building Material and Technology Promotion Council (BMTPC) promotes 24 alternative materials and technologies under the Ministry of Housing and Urban Affairs (MHUA).

HEAT WAVES

A Heat Wave is defined as a period of abnormally high temperatures, significantly exceeding the normal maximum temperature, especially during the summer season in the northwestern and south-central parts of India.

• The National Disaster Management Act (2005) and the National Policy on Disaster Management (2009) do not categorize heat waves as a natural disaster.

Criteria for Heat Waves (IMD Guidelines)

• Based on Departure from Normal Temperature:
  • Heat Wave: If the temperature departure from normal is between 4.5°C and 6.4°C.
  • Severe Heat Wave: If the temperature departure from normal exceeds 6.4°C.

Criteria for Declaring a Heat Wave

• Based on Actual Maximum Temperature (for plains only):
  • Heat Wave: Actual maximum temperature ≥ 45°C.
  • Severe Heat Wave: Actual maximum temperature ≥ 47°C.

The declaration of a heat wave requires the above conditions to be met at least in two meteorological subdivisions for two consecutive days, with the official declaration being made on the second day.

HEAT WAVES IN INDIA

Heatwave Proneness in India (Data and Spatiality)

• Data:
  • Range: Between 2014 and 2017, the average length of heatwaves in India ranged from 3-4 days, compared to the global average of 0.8-1.8 days.
  • Exposure: Indians experienced nearly 60 million heatwave exposure events in 2016, a jump of 40 million from 2012.
  • Increase in Temperature: According to the IMD, there was an increase of over 0.5°C in mean temperatures between 1901 and 2007. Forecasts suggest a rise in temperatures of 2.2-5.5°C across northern, central, and western India by the end of the 21st century.
• Spatial Distribution:
  • Core Heatwave Zone (CHZ): Heatwaves are common across Rajasthan, Punjab, Haryana, Chandigarh, Delhi, West Madhya Pradesh, Uttar Pradesh, Chhattisgarh, Orissa, Vidarbha in Maharashtra. The CHZ also includes parts of Gangetic West Bengal, Coastal Andhra Pradesh, and Telangana.
  • Less Prone Areas: Regions in the extreme north, northeast, and southwestern India are less prone to heatwaves.

Recent Heatwave Events

• 2015 Deadliest Heatwave:
  • Hyderabad recorded a temperature of 46°C (114.8°F) on May 21.
  • Delhi recorded 46.4°C (115.5°F) on May 25.
  • Prayagraj recorded 47.8°C (118°F) on June 9.
  • Bhubaneswar recorded 44°C (111.2°F) on June 10.

Note: The 2015 heatwave was the fifth deadliest on record, claiming over 2,400 lives.

• May 2020 Heatwave: Rajasthan, Delhi, Uttar Pradesh, Madhya Pradesh, and Maharashtra experienced severe to very severe heatwave conditions.

MARINE HEATWAVES (MHWS)

1. Frequency: Marine heatwaves have increased by 34% in frequency and 17% in duration between 1925 and 2016. Notably, this trend was observed in the 2015 Bay of Bengal event.
2. Decadal Change: The frequency of MHWs has increased by 50% over the past decade and has become more severe, with some lasting years.
3. Annual Occurrence: According to INCOIS, before, India experienced around six marine heatwave days annually, but this has now increased to nine or ten days annually.

Causes for Heat Waves

1. Anthropogenic Causes:
   • Urban heat island effect.
   • Deforestation.
   • Burning of fossil fuels.
   • Heavy industrialization.
   • Stubble burning.
2. Natural Causes:
   • Hot winds blowing from deserts with dry winds on the surface.
   • Anticyclone formations causing no cloud formation or thunderstorm activity, failing to balance the temperature.
   • Rising global temperatures due to climate change and global warming.
   • Shifts in air currents and weather patterns due to pressure belts’ shifting.
   • Depletion of the ozone layer.
   • Jet streams.
3. Marine Heat Waves:
   • Increasing Sea Surface Temperature: Prolonged warmer sea temperatures lead to marine heatwaves.
   • Breaks in Wind Patterns: Weak winds can trap heat at the ocean surface for longer periods.
   • El Niño: Contributing to rapid warming, especially in the Indian Ocean.
   • Carbon Emissions: Climate change leads to approximately 90% of warming from greenhouse gas emissions being absorbed by oceans.

Reasons for India Experiencing More Heat Waves

• Concretization of Land: Paved and concrete surfaces in urban areas, combined with lack of tree cover, increase ambient temperatures.
• Urban Heat Island Effects: These can make temperatures feel 3-4°C higher than actual readings.
• Rise in Global Temperature: Globally, temperatures have risen by an average of 0.8°C over the past 100 years, leading to increased heatwaves.
• Climate Change: Increasing daily peak temperatures and longer heatwave durations.
• Tropical Zone: Higher intensity of UV rays due to being located in a medium-high heatwave zone.
• High Rural Population: India’s large rural population, especially vulnerable to heat stress, contributes to the country’s susceptibility to heatwaves.

Impact of Heatwaves

1. Health Effects:
   • Dehydration: Heatwaves can lead to dehydration, which may contribute to serious health risks, such as acute cerebrovascular accidents (strokes) and thrombogenesis (blood clots).

• Heat cramps: Result in swelling (edema), syncope (fainting), and fever over 39°C (102°F).
• Heat exhaustion and heat stroke: Can cause fatigue, muscle cramps, dizziness, nausea, vomiting, and sweating.
• Psychological stress: Prolonged heat and extreme atmospheric conditions contribute to mental stress and can even result in death in extreme cases.

1. Environmental Effects:
   • Ecological damage: Reduced biological activity and carbon sequestration.
   • Wildfires: Heatwaves with low humidity contribute to droughts and fuel wildfires.
   • Coral bleaching: Increased temperatures cause coral bleaching in oceans.
   • Species extinction: Heatwaves may drive some species to extinction, while a few heat-resistant species may emerge.
   • Drought: Reduced moisture in soil leads to decreased evaporation and drought conditions.
2. Economic Effects:
   • Reduced human output: Decrease in labor efficiency due to high temperatures.
     • Example: India lost nearly 75,000 million labor hours in 2017 due to global warming.
   • Increased economic cost: More expenditure on cooling appliances.
   • Power outages: Sudden spikes in electricity demand can strain power grids.
   • Infrastructure damage: Heat causes materials like metal to expand, resulting in structural defects.
3. Social Effects:
   • Loss of lives: Heatwaves are deadly. For instance, from 2011 to 2018, heatwaves claimed 6,187 lives in India.
   • Reduced income: Increased temperatures reduce work efficiency, especially in vulnerable sectors like agriculture.
   • Food shortages: Heat can severely damage crops, leading to food insecurity.
   • Water access: Water lines may burst, causing water shortages.
4. Marine Heat Waves:
   • Habitat destruction: Marine heatwaves destroy marine habitats, forcing species like fish, whales, and sea turtles to migrate to cooler areas.
     • Example: The loss of kelp forests, seagrass habitats, and other ecosystems can last for decades, with cascading effects.
   • Forced migration: Marine heatwaves alter the natural migration behavior of marine species, affecting their reproduction and feeding patterns.

Heatwave Management Framework in India

1. Heat Action Plan (HAP):
   • Awareness: Public outreach to educate communities on the risks of heatwaves and appropriate safety measures.
   • Early Warning System: Set up early warnings for citizens before the onset of a heatwave to initiate precautionary actions.
   • Training: Capacity building for healthcare professionals (including paramedical staff and community health workers) to handle heatwave-related health issues.
   • Adaptive Techniques: Implement measures like providing potable water, cooling spaces, and night shelters for vulnerable populations.
2. NDMA’s Guidelines (National Disaster Management Authority):
   • Issued after the 2015 heatwaves.
   • Focus on preparing heat action plans, including:
     • Early warning systems.
     • Training healthcare professionals.
     • Public awareness campaigns.
     • Collaboration with NGOs and civil society to tackle heatwaves effectively.

Challenges in Heatwave Management

• No Statutory Recognition: Heatwaves are not recognized as disasters under India’s Disaster Management Act (2005), despite the increasing number of deaths and extreme weather events.
• Lack of Research: Insufficient use of district-level data to identify vulnerable areas for better-targeted interventions.
• Narrow Analysis of Urban Data: Limited understanding of intra-city vulnerability patterns, particularly at the ward level, hindering specific interventions.
• Underutilized Public Messaging Tools: Insufficient use of text messages, phone calls, and other automated alerts to disseminate information to the public.
• Lack of Public Awareness: Inadequate promotion of traditional adaptation methods (like staying indoors and wearing comfortable clothes).
• Half-hearted Attempts: Lack of comprehensive efforts to popularize climate-friendly designs (such as shaded windows, underground tanks, and insulating materials).
• Unavailability of Basic Services: Many areas still lack access to essential services like drinking water and indoor toilets, exacerbating the impact of heatwaves.

Way Forward for Heatwave Management

• Recognition under the Disaster Management Act (DM Act): Heatwaves must be recognized as disasters and included in the DM Act. This will equip central, state, and local bodies with statutory powers to enforce orders and access necessary resources.
• Sensitizing States: States should prepare and implement specific Heat Action Plans aligned with NDMA’s national guidelines on heatwaves.
• Early Warning System: Develop robust early warning systems to inform citizens of impending heatwaves. Public health information and guidelines must be made accessible to everyone.
• Focus on Vulnerable Groups: Special attention should be given to vulnerable populations, such as the urban poor, during heatwave planning and response.
• Urban Planning: Cities need to implement long-term urban planning measures for managing heatwaves, alongside short-term interventions.
• Sharing Best Practices: Stakeholders should share experiences and best practices to improve the overall effectiveness of Heat Action Plans.
• Data and Analysis:Collect more accurate and detailed data on heatwave deaths and illnesses to inform future responses and interventions. Analyze data based on demographics like age, gender, and occupation.
• Need for a Roadmap: A roadmap for India’s Heat Wave Management should be developed in line with broader global goals, including the Sustainable Development Goals (SDGs).