The urban heat island effect

TALLAHASSEE, Fla. (WCTV) — There’s a weather term that some may not be too familiar with: the Urban Heat Island effect. No, it’s not really an island. The term also doesn’t refer to a hot new nightclub coming to town (though not a bad name).

The urban heat island is an urbanized area with higher temperatures than the outer areas, according to the US Environmental Protection Agency. In other words, the city is usually a bit hotter than the suburbs or the rural area.

Rrecent analysis of Climate Central showed how the change in temperature can vary between a city and the outskirts of the city. Using research published in 2020Climate Central “created an index to evaluate the intensity of urban heat islands.”

They analyzed 159 cities in the US by determining what kind of land cover there was in each city, such as paved roads and green space such as trees and grass, and how much of that city each covered. Plants and trees can help cool the air because the leaves absorb some of the heat from the air, causing water to evaporate from the leaves (a cooling process).

They also took into account building height, which can affect how air moves through a city and how heat is dissipated, as well as population density. For example, a higher density of people usually means more use of air conditioning units that can add more heat to the outside air.

Other factors were reflection of light versus dark colored surfaces (albedo), and average width of the streets.

Analysis of Climate Central Central found that average temperatures between cities and their less developed environments ranged from 5 to 9 degrees Fahrenheit. The city at the top of the list was New Orleans, La. rated at 8.94 degrees with albedore reflectivity and coverage of impervious surfaces (e.g., roads, buildings, concrete, etc.) as the critical factors. Locations such as Miami and Chicago were tied at 7.24 degrees, with building height being one of the factors.

Tallahassee did not fall in the top 20 and had an average temperature index score of 5.8 degrees.

Analysis by Climate Central found that Tallahassee's heat island intensity score was 5.8ºF,…
Analysis by Climate Central found that Tallahassee’s heat island intensity score was 5.8ºF, better than the top 20 cities that ranged between nearly 9 bijna and just under 7º. The scores show the average temperature range between the city and the less developed environment.(Climate Central)

A warming world due to man-made carbon emissions would make the urban heat island worse. For instance, one study found that urban sprawl, on top of climate change, would increase the average city temperature in summer by 0.5 to 0.7 degrees Celsius and could rise to 3 degrees in some locations.

According to Climate Central, the additional heating would lead to a greater demand for air conditioning and therefore electricity. The extra energy consumption would not only put pressure on lower-income families, but also contribute to adding more carbon into the atmosphere and contribute to the global warming problem.

Long-term solutions to reduce heat in cities include planting more trees. Climate Central also said adding vegetation to roofs, or what are termed as green roofs, gives more shade and lower temperatures on the roof. Adding reflective materials to roofs would also help.

The city of Tallahassee does offer incentives to better deal with the heat on roofs, according to the EPA. Installing a reflective metal or shingle “cool roofs” to reduce energy consumption in the summer months would qualify for a loan through the city, among other improvements.

As climate change and urban sprawl threaten to exacerbate urban heat, there are ways to limit how hot it can get.

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