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Urban Heat Island Effect: How to Prevent It
Summer temperatures are finally upon us, and this summer is shaping up to be one of the hotter ones on record (though with global climate change in full swing, this shouldn’t come as a surprise anymore). Heatwaves in much of the country's Southeast part have led to temperatures in the triple digits in May, foreshadowing what could be a pattern for the rest of the summer. For people who live in congested, urban areas, extreme heat can be much more dangerous, as the heat in cities tends to be much more severe.
The urban heat island effect, a well-documented phenomenon, can drastically raise summer temperatures to even more extreme levels. Mercifully, there are things that every urban homeowner can do to help reduce the heat and humidity in the city this summer.
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What is the Urban Heat Island Effect?
Heat island describes urban areas that are warmer than neighboring rural areas. The Environmental Protection Agency (EPA) states that a city's annual mean air temperature with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings. At night, the difference can be as high as 22°F (12°C). Heat islands can affect communities by increasing peak energy demand during the summer, including air conditioning costs, air pollution, greenhouse gas emissions, heat-related illness and mortality, and water quality.
Across the United States, over two-thirds of significant cities are warming during the summertime at a quicker rate than rural counterparts. Las Vegas, Albuquerque, and Denver are the three cities that most suffer from the urban heat island effect. Las Vegas routinely experiences heat over 7 degrees warmer than the surrounding desert landscape. In addition, due to the urban heat island effect, cities are at a much higher risk of suffering summer days of extreme temperatures. During the past decade, metropolitan areas across the United States experienced at least eight more days, with temperatures soaring above 90 degrees than nearby rural areas.
Urban heat islands essentially follow the path of urban sprawl. As vegetated, rural areas covered with forests, grasslands, and farmlands are cut down, torn up, and replaced with concrete and asphalt structures. The sun’s heat is absorbed, and temperatures inevitably begin to rise. All plant life (and especially trees) play an important role in temperature regulation by absorbing carbon dioxide and evaporating water into the air. On the other hand, concrete and asphalt contribute to higher temperatures by absorbing the sun’s heat instead of reflecting it into the atmosphere. In metropolitan areas, the tunnels of skyscrapers and large buildings trap the hot afternoon heat and significantly reduce wind and airflow. The emissions from hundreds of thousands of vehicles, factories, air conditioners, and other elements of our modern-day civilization contribute to the warming of the urban landscape.
The higher summer temperatures that come with the urban heat island effect have been tied to higher levels of ozone pollution, which can pose a severe health risk for people in the city. With around 80 percent of all Americans living in metropolitan areas, combined with warmer summer temperatures associated with global climate change, the urban heat island effect will only continue to worsen in many regions across the country. Finding ways to reduce the worst effects of urban heat islands is essential to making our summer temperatures bearable.
Strategies to Reduce Urban Heat Island Effect
Here are a few ideas about what you and your neighbors can do to reduce rising temperatures.
Cool Roofs
Though not as effective as green roofs in reducing the urban heat island effect, cool roofs can play an essential role in keeping your home cooler during the summertime. These types of roofs are made of materials (or include surface coatings on top of an existing roof) that will reflect sunlight and heat back into the atmosphere, thus keeping your home and the surrounding area cooler. For example, EPDM (rubber membrane) roofs, typically black, can be purchased in white for no additional cost.
Tobias Roberts
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.
