Urban Heat Island Effect

If you have ever noticed that it was hotter in a heavily developed area compared to a mostly natural, nearby area, then you have experienced the “heat island effect”. The heat island effect describes the phenomenon where there are pockets of higher temperatures. The heat island effect mostly occurs in cities, where the built environment absorbs sunlight and radiates heat back into the environment. Since cities have significantly more buildings, roadways, and man-made structures than rural areas, they hold on to more heat than rural areas over a longer period of time.

The heat island effect can have an impact on public health due to extreme heat. Extreme heat can cause heat stroke, heat exhaustion, and heat cramps, among other health impacts. The higher temperatures also lead to higher energy consumption for cooling. Therefore, addressing the heat island effect would also improve public health and could lead to reducing energy consumption.

Miami Beach Temperatures

The Miami, Florida area experienced its hottest week on record in June 2020. And nine of Miami’s 10 hottest days since 1937 have occurred in the past three years. These trends point to a global phenomenon of a climate speedily heating up. September 2020 was the hottest month worldwide on record since 1880, according to the National Oceanic and Atmospheric Administration (NOAA).

This trend is expected to continue if current conditions persist. The National Aeronautics and Space Administration (NASA) has released data outlining how temperature and rainfall patterns could change throughout the world through the year 2100 due to mounting levels of greenhouse gases being emitted in the Earth’s atmosphere. Summers in the majority of the United States are now warmer that they were in the 1970s. If current emission trends continue, Miami Beach will have 72 more days above 95° by 2100.

Weather describes the conditions in the atmosphere in an area over a short period of time. The weather can fluctuate from day to day and minute to minute. On the other hand, climate is the long-term pattern of weather in a region. A change in climate requires persistent changes in weather conditions over a long period of time. Persistent increasing temperatures are projected to spur a change in climate worldwide.

There is scientific consensus that human activities are causing greater temperature increases than have historically naturally occurred. Population growth has led to a global increase in energy consumption which has released growing levels of greenhouse gas emissions into the atmosphere exacerbating the greenhouse effect.

The greenhouse effect has a vital role in regulating the temperature on Earth’s surface but higher levels of greenhouse gas emissions are absorbing more heat and causing higher temperatures throughout the planet. In the United States, daily record high temperatures are surpassing daily record low temperatures. A study by the Florida Climate Center found that weather stations in Miami measured a hot season that has increased by at least three weeks between 1950 and 2007. Since Miami Beach is an urban city, the higher temperatures may feel even hotter due to the heat island effect.

Reducing Urban Heat Island

A great way to reduce the heat island effect while also providing additional environmental and aesthetic benefits is to increase the urban canopy. Planting trees, shrubs, and ground cover can contribute to lowering temperatures in an urban area by providing shade and helps to reduce the amount of heat absorbed by the asphalt and concrete from roadways and buildings. These trees and plants also contribute to stormwater management and the absorption of carbon dioxide and provide habitat to nearby species.

Another method for reducing the heat island effect is to choose lighter-colored building materials or those that have a higher albedo. For example, a white roof absorbs less sunlight than a dark roof. This allows the building and surrounding area to remain cooler. Similarly, sustainable roofing systems such as green roofs and blue roofs are great options to reduce the heat island effect.

Urban Heat Island Ordinance

In March 2019, the City of Miami Beach adopted the Urban Heat Island Ordinance (2019-4252) which requires new construction to install a sustainable roofing system. Sustainable roofing systems can be solar roofs, blue roofs, cool roofs, green roofs, and other roofing systems that will reduce the heat island effect, allow reuse or retention of stormwater or reduce greenhouse gases.

The Ordinance also waives public hearing fees for the installation of sustainable roofing systems, solar carports, porous pavement, and cool pavement and provides a height exception for solar roof installations that shall not exceed 25 feet above the height of the roofline of the main structure for all districts except single-family residential districts which shall not exceed 5 feet.

2019-4252 Ordinance Urban Heat Island

Cool Streets Projects

The cool street located at 1664 Meridian Avenue (P27) is an innovative solution to test the reduction of extreme heat in our city.

A cool street is a street whose surface is a light color and reflects sunlight. In contrast, most streets are dark and absorb sunlight which traps heat. A section of the P27 parking lot have been covered with a reflective coating. The efficacy of this technology will be measured against the standard lot.

Cool streets have been shown to reduce the surface temperature of streets and surrounding areas which helps to keep communities cooler. As part of the Extreme Heat Resilience Alliance (EHRA), we are committed to finding solutions to extreme heat and combat its negative impacts.

FINAL_Cool Street Sign

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