It’s going to be another sweltering day in New York City, where the summer’s second heat wave continues to drag on.
It’s been so hot that the city’s infrastructure is showing just how not up to task of functioning in extreme heat it really is: the Third Avenue Bridge, a rotating bridge running between Manhattan and the Bronx that can swing out to let taller ships pass by, got stuck in the open position on Monday after the entire structure swelled in the high temperatures, making it too long to swing back close.
Thursday’s forecast says that the borough could hit 90 degrees — a dangerous high temp that, according to a new study, is nearly 10 degrees hotter due to the built environment of an urban neighborhood like the Bronx.
It has long been understood that cities are hotter than areas with more greenspace and less development due to what’s called the urban heat island effect.
Essentially, the concrete, asphalt, brick and cinder block, and other energy-absorbing materials that cities are made from trap and hold heat rather than reflecting or absorbing it and allowing it to dissipate.
Just think of how a sidewalk or parking lot surface can get so hot that it almost shimmers — such surfaces can be markedly hotter than the air temperature (the number you see on the weather forecast), and when you have a whole city radiating heat back into the air on a hot, hot day, it bumps the temperature up significantly.
Now, a new study from the non-profit Climate Central shows just how much the heat-island effect contributes to local temps in cities across the country. According to the study, more than 5 million people live in urban areas that can be at least 10 degrees hotter due to the effects of the built environment.
The study looked at 65 cities, and found that on average the temperature was 8 degrees higher across the board due the urban heat island effect. Out of the top 10 cities with the highest bump in temperatures, seven have significant Black populations: New York, Newark, Chicago, Philadelphia, Washington D.C., Boston , and Baltimore. Miami, a city that historically has had a significant Black population, is also in the top 10.
The study notes how the history of redlining continues to be felt in terms of hotter temperatures in such neighborhoods, pointing to an analysis done by researchers at Columbia University that found redlined neighborhoods are hotter in 150 out of 179 major cities in the country.
“What we end up seeing is this vicious cycle of how a federally codified policy from the 1930s has a long legacy effect to what we’re seeing today. The communities that live around these areas are the ones who face it worst when a heatwave comes through.” Vivek Shandas, a professor of climate adaptation at Portland State University who worked on the study, told The Guardian.
But what the Climate Central research shows is that while redlining is a factor, it is one of many, and the increase in heat presents very differently depending on which city you’re looking at.
In some places, like Cincinnati, the hotter temperatures are largely confined to the urban core, while in Houston they spread across the city’s sprawl. Chicago, rather unexpectedly, is very diffuse in terms of which neighborhoods experience the highest increase, with many wealthier North Side communities more than 8.5 degrees hotter due to heat-island effect, and the Southwest Side of Chicago seeing a lower increase.
While air conditioning would appear to be the most obvious solution to beating the hotter heat in cities, cooling private homes and apartments with a/c units actually exacerbates the issue: the report notes that air conditioned buildings in a city can increase the outside heat by as much as 20%. Instead, more systemic and holistic changes are needed: more greenspace, more tree cover, energy-efficient heat pumps instead of air conditioning, and a built environment that can reflect heat instead of trap it — which can be as simple as making rooftops white instead of black.