What are heat islands?

Imagine being in a crowded room with people and objects that surround you. Unlike an open landscape, the area that you are in feels quite warmer in temperature, sometimes to a point where it causes an individual to feel uncomfortable. This feeling can be described as physiological as your body temperature heats up or it can be described as psychological as you become anxious. This simple metaphor, though at a smaller scale, is a representation of a prominent issue that scientists have coined the Heat Island Effect. 

According to the Environmental Protection Agency, heat islands are basically any urbanized or metropolitan area that experiences temperatures that are much higher than outlying areas.¹ In a heat island, infrastructure plays a significant role in absorbing and re-emitting the sun’s energy at higher amounts than natural landscapes such as a forest or bodies of water.² These urban areas are usually highly concentrated with buildings, roads, and people and often have limited green spaces available to the public. These heat islands can form at any time of the day, regardless of the size of the city, and can happen in any season.³ Climate data has shown that “neighborhoods in a highly-developed city can experience mid-afternoon temperatures that are 15℉ to 20℉ hotter than outlying areas with more vegetation and less development.”⁴ Figure 1 helps to highlight the temperature variability from urban heat islands and how it differs between one’s location and the time of day. There are a variety of negative consequences related to heat islands, which will be discussed later, but first, we will look at what influences the development of heat islands. 

Figure 1: Urban Heat Islands Temperature Infographic

There are a variety of factors that contribute to urban heat islands. For one, urban areas tend to have a reduced natural landscape. Without trees, vegetation, and bodies of water to help cool the air and provide shade, temperatures are likely to increase in that area. Second, urban heat islands form as a result of the properties used in urban materials. In urban environments, pavements and roofing often reflects less energy from the sun and instead absorb and emit more heat than vegetation. This results in a slow release of heat and an increase in temperatures. Third, the structure and placement of buildings (urban geometry) block natural wind which is needed for cooling and the buildings absorb lots of heat that are not released. Fourth, urban environments tend to have greater amounts of human activity. Anything from vehicle use to industrial facility practices contributes to emitting heat and adding to the heat island effect. Lastly, weather and geography play an important role since calm conditions result in more heat and minimize how much heat can be released. If a city is in a valley, it may be more difficult for wind to come into the valley or escape, therefore the heat will increase.⁵ 

Urban heat islands (UHIs)  are extremely dangerous and pose a threat to public and environmental health in a number of ways. For example, UHIs have the ability to increase air pollution and create conditions that are dangerous for individuals who live or work in these areas. Without access to air conditioning, working in an urban environment could be harmful to one’s health. In addition, discriminatory housing practices, such as redlining, have led to a disproportionate impact on communities of color.⁶ A study published in Nature Communications found that in nearly every major city in the United States, there were disparities between people of color and whites which showcased that the average person of color was more likely to be exposed to a heat island. Furthermore, the study generalized the health effects, suggesting that urban heat islands contributed to a variety of “heat-related deaths and illnesses such as stroke, respiratory difficulty, cramps, and exhaustion.”⁷

Figure 2: The Urban Heat Island Effect

Not only do UHIs have a negative direct impact on human health, but there are a variety of impacts on the environment, the economy, and the general quality of life. Firstly, urban heat islands require an increased demand for air conditioning, and studies have found an increase of 1-9% for every 2℉ increase in temperature. As a result, electricity expenses are likely to increase much higher even though all individuals are not able to afford these increases. Connected to electricity are companies that rely on fossil fuel power plants. As the demand for electricity increases, these plants will increase their fossil fuel consumption which leads to an increase in greenhouse gas emissions such as carbon dioxide, which will have a direct impact on global climate change. Lastly, the higher temperatures in urban heat islands will have an impact on the temperature of stormwater runoff. As the water gets heated up and is released into bodies of water, aquatic life is likely to experience negative impacts related to metabolism, reproduction, and more. If the issues of urban heat islands are not addressed, humans and the environment will continue to face these negative impacts head-on.⁸

Over the next 3 months, I want to explore many of the solutions that are available to combat the urban heat island effect. In doing so, I will make sure to address the issue as it relates to sustainability, making sure to address all of the contents necessary. For reference to the research I will be doing, it is important to have the definition of sustainability at hand. Sustainability is: 

A practice, process, or entity is sustainable if its initiatives, actions, or impacts work to meet the social, environmental, and economic needs of the present without compromising the ability of future generations to meet their own needs by ensuring:

• resource use that maximizes renewal, encourages re-use, and minimizes waste while protecting and restoring the health of natural systems including the protection of biodiversity, reducing pollution, and mitigating global climate change;
• equitable economic opportunity that empowers all people to meet their own needs;
• that essential social goals or foundations for humanity to prosper including basic human rights are met.

Best practices for meeting these objectives include using an inclusive, transparent, and equitable process that employs systems thinking and scientific principles, encourages individual and collective action, and assessment using measurable indicators and establishes accountability.

Using this definition, I will explore solutions and determine if it fits within the criteria stated above to help address the problem of urban heat islands. 

Next -> Systems Thinking

Endnotes

1.  Environmental Protection Agency. (2022a). Learn About Heat Islands. Retrieved February 11, 2022, from https://www.epa.gov/heatislands/learn-about-heat-islands

2.  Environmental Protection Agency. (2022a). Learn About Heat Islands. Retrieved February 11, 2022, from https://www.epa.gov/heatislands/learn-about-heat-islands

3.  Environmental Protection Agency. (2022a). Learn About Heat Islands. Retrieved February 11, 2022, from https://www.epa.gov/heatislands/learn-about-heat-islands

4.  Urban heat islands. (2021, July 14). Retrieved February 11, 2022, from https://medialibrary.climatecentral.org/resources/urban-heat-islands

5.  Environmental Protection Agency. (2022a). Learn About Heat Islands. Retrieved February 11, 2022, from https://www.epa.gov/heatislands/learn-about-heat-islands

6.  Urban heat islands. (2021, July 14). Retrieved February 11, 2022, from https://medialibrary.climatecentral.org/resources/urban-heat-islands

7.  Costley, D. (2021, May 25). People of Color More Exposed to Heat Islands, Study Finds. Retrieved February 11, 2022, from https://www.usnews.com/news/health-news/articles/2021-05-25/people-of-color-more-exposed-to-heat-islands-study-finds#:~:text=A%20new%20study%20finds%20that,city%20in%20the%20United%20States.&text=May%2025%2C%202021%2C%20at%2011%3A00%20a.m.&text=In%20nearly%20every%20major%20city,people%2C%20a%20new%20study%20found.

8.  Environmental Protection Agency. (2022b.). Heat Island Impacts. Retrieved February 11, 2022, from https://www.epa.gov/heatislands/heat-island-impacts