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WHAT CAN WE DO ABOUT EXTREME HEAT IN CITIES

Updated: Feb 26


The huge areas of concrete and asphalt, the absence of green spaces, the suspended particles and the GHG emissions, plus human activities which emit heat to the atmosphere, are responsible for the excess heat recorded in cities when compared with rural or suburban areas in the same geographical location.

 

This results in a phenomenon called Urban Heat Island (UHI) which is a phenomenon that occurs in almost all metropolitan cities in the world. It is a local event which, added to global warming, requires cities more than anywhere else, to adapt to extreme heat.

 

The heat island reaches its maximum intensity during the night, when urban structures emit heat, they have accumulated during the sunshine hours. This can generally result in temperatures rising by 2ºC. A recent study by the Swiss meteorological service, however, estimated the difference in temperature between a city and rural area to be around 6°C.

The UHI phenomenon , of course, occurs in Jakarta, the capital city of Indonesia, a metropolitan city with an area of 662km2, 12 million inhabitants and an average population density of 16,000 per km2.



Anthropogenic activities of urban growth and development in Jakarta have caused increasingly uncomfortable climatic conditions and tend to be warmer and potentially cause the urban heat island (UHI) effect. This phenomenon can be monitored by observing the air temperature measured by meteorological stations, but the scope is relatively limited. Therefore, the utilization of remote sensing data is very important in monitoring the UHI with wider and more effective coverage. In addition, the remote sensing data can also be used to map the pattern of changes in environmental conditions (microclimate).

 

This study aimed to analyse the effect of changes in environmental conditions (land use/cover, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Build-up Index (NDBI)) toward the spread of the urban heat island (UHI). In this case, the UHI was identified from pattern changes of Land Surface Temperature (LST) in Jakarta based on data from remote sensing. The data used was Landsat 7 in 2007 and Landsat 8 in 2013 for parameter extraction environmental conditions, namely: land use cover, NDVI, NDBI, and LST. The analysis showed that during the period 2007 to 2013, there has been a change in the condition of the land use/cover, impairment NDVI, and expansion NDBI that trigger an increase in LST and the formation of heat islands in Jakarta, especially in the area of business centres, main street and surrounding area, as well as in residential areas.


Elevated Emissions of Air Pollutants and Greenhouse Gases

As described above, heat islands raise demand for electricity in summer. Companies that supply electricity typically rely on fossil fuel power plants to meet much of this demand, which in turn leads to an increase in air pollutants and greenhouse gas emissions.

 

These pollutants are harmful to human health and contribute to complex air quality problems such as the formation of ground-level zone (smog), fine particulate matter and acid rain. Increased use of fossil-fuel-powered plants also increases emissions of greenhouse gases, such as carbon dioxide, which contribute to global climate change.

 

In addition to their impact on energy-related emissions, elevated temperatures can directly increase the rate of ground-level ozone formation. Ground-level ozone is formed when nitrogen oxides and volatile organic compounds react in the presence of sunlight and hot weather. If all other variables are equal, such as the level of precursor emissions in the air and wind speed and direction, more ground-level ozone will form as the environment becomes sunnier and hotter.


Compromised Human Health and Comfort

Heat islands contribute to higher daytime temperatures, reduced nighttime cooling and higher air-pollution levels. These in turn, contribute to heat-related deaths and heat-related illness such as general discomfort, respiratory difficulties, heat cramps, heat exhaustion and non-fatal heat stroke.

Heat islands can also exacerbate the impact of naturally occurring heat waves, which are periods of abnormally hot and often humid weather. Sensitive populations are particularly at risk during these events.


Older adults are among the most vulnerable to extreme heat events. Many physiological, psychological, and socioeconomic factors contribute to this danger. Older adults are more likely to be in poor health, to be less mobile and more isolated, to be more sensitive to high heat, and to live on reduced incomes.


Young children tend to be more susceptible to extreme heat due to their small size and other characteristics. Children’s more rapid breathing rates relative to body size, time spent outdoors, and their developing respiratory systems raise their chances of aggravated asthma and other lung diseases caused by ozone air pollution and smog, which usually increases during heat waves.

 

Populations with low-income are at greater risk of heat-related illnesses due to poor housing conditions, including lack of air conditioning and small living spaces, and inadequate resources to find alternative shelter during a heat wave.

 

People who spend their working hours outdoors are more prone to conditions such as heat exhaustion and heat stroke. They have higher exposures to ozone air pollution and heat stress, especially if work tasks involve heavy exertion.

 

People in poor health, including people with chronic conditions, disabilities, mobility constraints, and those taking certain medications, are vulnerable to extreme temperatures. People with diabetes, physical impairments, and cognitive deficits are especially at-risk during heat waves.

 

Follow the tips below to help reduce the heat island effect and improve your community’s resilience to heat waves.



1.Increase shade around your home

Planting trees and other vegetation lowers surface and air temperatures by providing shade and cooling through evapotranspiration. Trees and vegetation that directly shade your home can decrease the need for air conditioning, making your home more comfortable and reducing your energy bill. Trees also protect your family’s health by improving air quality, by providing cooling shade for outdoor activities, and reducing exposure to harmful UV radiation.

 

2.Install green roofs

A green roof, or rooftop garden, is a vegetative layer grown on a rooftop. Green roofs provide shade and remove heat from the air through evapotranspiration, reducing temperatures of the roof surface and the surrounding air. Green roofs absorb heat and act as insulators for your home, reducing energy needed to provide cooling and heating (which decreases your energy bill), improving indoor comfort, and lowering heat stress associated with heat waves.

 

3.Install cool roofs

Cool (or reflective) roofs help to reflect sunlight and heat away from your home, reducing roof temperatures. This allows for your home to stay cooler, reducing the amount of air conditioning needed during hot days.

 

4.Use energy-efficient appliances and equipment

Using efficient appliances and equipment in your home can help to lighten the load on the electric grid during heat waves, thus ensuring a more reliable supply of electricity to your community.

These are some of the simpler ideas to reduce the effect of UHI on your home and we hope this will help you to reduce your energy usage as well as enjoy cooler living conditions.

 

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