Each year when the summer hits many New Yorkers pack their bags and wave sayonara to the city, and they do so for one reason: to escape the scorching heat. As we profusely sweat through the third heat wave of what is one of the hottest summers of our lifetime, we’re just over here wondering “why is NYC so damn hot?!”
Four words for you: urban heat island effect.
According to the United States Environmental Protection Agency, urban heat islands are “are urbanized areas that experience higher temperatures than outlying areas.”
When natural land covers are replaced with dense concentrations of pavement, buildings, and other surfaces they absorb and retain heat and then re-emit the sun’s heat more than natural landscapes, making these areas hotter than rural environments.
And you can definitely feel the difference–the EPA writes that daytime temperatures in urban areas are about 1–7°F higher than temperatures in rural areas, and nighttime temperatures are about 2-5°F higher
And now a new study by Climate Central has found that New Yorkers feel this heat more than anyone else in the country.
Climate Central communicates climate change science, effects, and solutions to the public, and they recently analyzed how and where urban heat islands boost temperatures within 65 major U.S. cities. And while the planet as a whole is warming due to human-caused climate change, “the built environment further amplifies both average temperatures and extreme heat in cities.”
So, to better understand the role that the built environment plays in making us feel like we’re actually being cooked like a rotisserie chicken, they calculated the urban heat island (UHI) index for every census block group within each city.
To clarify, Climate Central writes that “UHI index values are estimates of how much the urban built environment boosts temperatures.” Or, in other words, it’s an estimate of the additional heat urban areas receive beyond just what the temperatures show.
The three biggest factors that influence UHI index are:
- Albedo – the fraction of incoming solar radiation reflected by a surface (for example, surfaces like roads have a low albedo and therefore absorb sunlight and radiate it back into the city as heat)
- Percentage of green space – plants can reduce peak summer temperatures by 2°F to 9°F in urban areas!
- Population density – transportation, industrial facilities, and the cooling of buildings causes extra heat
But getting back to the main question: Why is NYC so f&%*ing hot right now?!
Well, Climate Central found that while the 68% of the 50 million people included in their analysis are living in census block groups with an UHI index of 8°F or higher, NYC’s UHI index was the highest of the 65 cities looked at, coming in at 9.7°F.
And when looking at NYC’s population specifically, 83% of us are living within this UHI index (and this is the hottest neighborhood in all of NYC).
Even more, NYC is one of only “six cities that had at least 1 million people exposed to an UHI index of 8°F or higher — meaning that on a day when temperatures in a park outside the city are 90°F, it feels like 98°F or higher for at least 1 million people in the city.”
So, while us New Yorkers are constantly looking for ways to stay cool in the suffocating heat–especially when heat wave after heat wave keep smothering us–there are also some long-term solutions that can be taken to the city as a whole to mitigate the heat, including:
- Planting trees – particularly along paved streets
- Implementing green roofs, or rooftop gardens
- Implementing cool roofs made of highly reflective (i.e., high albedo) and emissive materials
- Implementing cool pavements – an alternative to conventional concrete or asphalt which are instead reflective and/or permeable to help reduce surface temperatures
The full study can be found here.