by Jennifer R. Cox, Associate Planner and Manager of GIS, RPA
During recent heat waves, you may have noticed on weather.com or the nightly television news that the city was much hotter at night than many parts of the surrounding region. On one typical night at 10 p.m., for example, it was a sweltering 87F at LaGuardia, while a mere hour away in Port Jervis, NY it was a cool 72F. For days this pattern persisted with no relief in sight. Why was the city not cooling off at night?
It's simple: living surrounded by concrete and brick, and the constant hustle and bustle of human activity (such as cars, trains, or air conditioners) means outside temperatures will be considerably higher than if you were surrounded by grass and trees.
These differences in regional temperature are what climate scientists call the urban heat island (UHI) effect. Best seen in the evening, UHI is a result of buildings and streets trapping heat over the course of a day and slowly re-releasing the heat after the sun goes down. Not only does a building passively trap heat, but it actively produces heat, as lights, computers and air conditioners send out immense quantities of additional heat, which in turn raise already high outside temperatures. What we get are hot nights in the big apple!
As city dwellers we all feel this excess heat, and inherently veer away from things like bus or car exhaust and air-conditioner vents, which can warm surrounding air by more than 10 degrees. What's particularly insidious about the UHI effect is that it becomes more extreme as temperatures become more extreme. As temperatures near 100, people retreat inside and turn air conditioners up, which put out even more heat, thus raising outside temperatures and prompting more people to retreat inside and turn on their air conditioners.
And so on. The end result is often record breaking consumption rates and subsequent power failures. These conditions are not particular to the New York region. They have affected hundreds of millions of people in urban environments all over the world. UHI impacts energy demand. With more energy demand, urban heat islands are also contributing to climate change by increasing the demand for electricity to cool our buildings.
But among the concrete and brick are signs of hope - cool islands, such as Central Park or one of the many tree lined streets. These cool islands are especially evident during the heat wave when afternoon temperatures could be 95F in Central Park, while 99F in Lower Manhattan, and 102F in Newark, NJ. They are reminders that weather and climate over a short distance do not impact us all equally.
So what can be done to reduce the urban heat island effect? One thing to do is simply to be aware of it. Awareness can prompt a fine tuning of remedies to beat the heat. Urging people to conserve energy by turning off building lights and setting air conditioners on higher temperature levels or changing old appliances to ones with the Energy Star label will reduce the UHI effect. These conditions are taken so seriously in Tokyo, they have perpetuated a cultural change allowing businessmen to remove suit jackets in order to lower air conditioning demand.
On a longer term basis, the way to reduce UHI substantially is to "green" the city. This can mean bringing more of the country into the city, such as planting grass and trees on rooftops and shade trees along sidewalks. New Jersey has found a cooler path, with its Cool Cities Initiative run by New Jersey Community Forestry Program and the Green Streets Cool Schools Program. It also can mean adopting "green" building and infrastructure standards, which produce buildings with cool roofs and even sidewalks that keep cooler with less energy. Or it can mean all of the above.
Cool Community programs, such as the Cool Houston Plan, include cool roofing, cool paving, and cool landscaping, and are supported by US Environmental Protection Agency (EPA). Here in New York, the new Hearst Tower, the new Goldman Sachs building in Lower Manhattan and the new Bank of America building in Midtown are expected to receive certificates from the US Green Buildings Council's Leadership in Energy and Environmental Design (LEED) program. These buildings provide good examples of change, but it will take a lot more such buildings to have an impact on the UHI effect.
If we keep planting trees on roofs and sidewalks, changing building design, and turning down air conditioners, then keeping cool may no longer take so much energy, which in the end will make keeping cool not so difficult.
For more information see www.epa.gov/heatisland/ and www.hotcities.org.
During recent heat waves, you may have noticed on weather.com or the nightly television news that the city was much hotter at night than many parts of the surrounding region. On one typical night at 10 p.m., for example, it was a sweltering 87F at LaGuardia, while a mere hour away in Port Jervis, NY it was a cool 72F. For days this pattern persisted with no relief in sight. Why was the city not cooling off at night?
It's simple: living surrounded by concrete and brick, and the constant hustle and bustle of human activity (such as cars, trains, or air conditioners) means outside temperatures will be considerably higher than if you were surrounded by grass and trees.
These differences in regional temperature are what climate scientists call the urban heat island (UHI) effect. Best seen in the evening, UHI is a result of buildings and streets trapping heat over the course of a day and slowly re-releasing the heat after the sun goes down. Not only does a building passively trap heat, but it actively produces heat, as lights, computers and air conditioners send out immense quantities of additional heat, which in turn raise already high outside temperatures. What we get are hot nights in the big apple!
As city dwellers we all feel this excess heat, and inherently veer away from things like bus or car exhaust and air-conditioner vents, which can warm surrounding air by more than 10 degrees. What's particularly insidious about the UHI effect is that it becomes more extreme as temperatures become more extreme. As temperatures near 100, people retreat inside and turn air conditioners up, which put out even more heat, thus raising outside temperatures and prompting more people to retreat inside and turn on their air conditioners.
And so on. The end result is often record breaking consumption rates and subsequent power failures. These conditions are not particular to the New York region. They have affected hundreds of millions of people in urban environments all over the world. UHI impacts energy demand. With more energy demand, urban heat islands are also contributing to climate change by increasing the demand for electricity to cool our buildings.
But among the concrete and brick are signs of hope - cool islands, such as Central Park or one of the many tree lined streets. These cool islands are especially evident during the heat wave when afternoon temperatures could be 95F in Central Park, while 99F in Lower Manhattan, and 102F in Newark, NJ. They are reminders that weather and climate over a short distance do not impact us all equally.
So what can be done to reduce the urban heat island effect? One thing to do is simply to be aware of it. Awareness can prompt a fine tuning of remedies to beat the heat. Urging people to conserve energy by turning off building lights and setting air conditioners on higher temperature levels or changing old appliances to ones with the Energy Star label will reduce the UHI effect. These conditions are taken so seriously in Tokyo, they have perpetuated a cultural change allowing businessmen to remove suit jackets in order to lower air conditioning demand.
On a longer term basis, the way to reduce UHI substantially is to "green" the city. This can mean bringing more of the country into the city, such as planting grass and trees on rooftops and shade trees along sidewalks. New Jersey has found a cooler path, with its Cool Cities Initiative run by New Jersey Community Forestry Program and the Green Streets Cool Schools Program. It also can mean adopting "green" building and infrastructure standards, which produce buildings with cool roofs and even sidewalks that keep cooler with less energy. Or it can mean all of the above.
Cool Community programs, such as the Cool Houston Plan, include cool roofing, cool paving, and cool landscaping, and are supported by US Environmental Protection Agency (EPA). Here in New York, the new Hearst Tower, the new Goldman Sachs building in Lower Manhattan and the new Bank of America building in Midtown are expected to receive certificates from the US Green Buildings Council's Leadership in Energy and Environmental Design (LEED) program. These buildings provide good examples of change, but it will take a lot more such buildings to have an impact on the UHI effect.
If we keep planting trees on roofs and sidewalks, changing building design, and turning down air conditioners, then keeping cool may no longer take so much energy, which in the end will make keeping cool not so difficult.
For more information see www.epa.gov/heatisland/ and www.hotcities.org.
@RegionalPlan