Why are Cities Getting Hotter?

Why are cities such as Los Angeles significantly hotter than surrounding rural areas? Large cities and densely populated areas are highly developed; buildings and infrastructure have replaced what once was open land and vegetation. Due to increased human activity, energy consumption and expanding infrastructure, cities have become much hotter than surrounding areas and form an “island” of heat.

These islands of heat, also known as urban heat islands, cost residents more in energy bills and create harsher living conditions due to excess heat. According to the Environmental Protection Agency (EPA), heat islands also affect communities by increasing air pollution, greenhouse gas emissions, heat-related illness, mortality, and reducing water quality.

Over the last two decades extreme heat has become more frequent across the United States mainland. This interaction of increased temperatures and the heat island effect has the potential to become increasingly harmful to people’s health and quality of life. In addition to the harmful health risks imposed by heat islands, National Geographic states that the Los Angeles heat island costs the city $100 million a year in energy.

On a hot summer day, black pavement can reach temperatures in excess of 160 degrees Fahrenheit and are believed to be a contributing factor to urban heat islands. The EPA states that reflective pavements, such as CoolSeal by GuardTop®, can help mitigate heat islands. 1

CoolSeal is designed to reflect the sun’s energy to produce cooler surface temperatures through increased reflectivity and improve comfort and safety for people and animals on playgrounds, walking paths, schools, neighborhoods, bike trails and other community areas. Due to CoolSeal’s reflective properties and lighter color, it may reduce surface temperatures by 10-25 degrees Fahrenheit (under certain conditions).

According to the EPA, reflective pavements such as CoolSeal can reduce the temperature of storm water runoff and improve water quality, increase nighttime visibility, improve local comfort, and reduce lighting requirements which saves energy and money. 1

In addition to implementing cool pavements, there are several other ways that communities can work together to help reduce the effects of heat islands. Cities and residents can plant trees and vegetation around homes and neighborhoods, install rooftop gardens and cool roofs, and use energy efficient appliances. Through these small steps and increased awareness, we can reduce our carbon footprint and help to diminish heat islands.

[1] U.S. Environmental Protection Agency. 2012. Reducing urban heat islands: Compendium of strategies. Draft. https://www.epa.gov/heat-islands/using-cool-pavements-reduce-heat-islands