- It's hot.
I think it's even hotter here.
We're out in New York City,
investigating a big problem that's hiding in plain sight.
It's hot, too hot,
and not just because it's summertime.
Cities everywhere, not just New York,
are basically running fevers.
They're up to 22 degrees Fahrenheit hotter
than surrounding rural areas.
It's a phenomenon called the urban heat island effect
and it has serious consequences for cities
and their residents.
That's actually horrifying.
So we'll take a reading on the asphalt.
Surface temperatures are hotter here in New York City
than they are in nearby Woodstock
and other parts of the Hudson Valley.
This map, generated from satellites,
shows us that New York City is an urban heat island.
You'll notice that New York and nearby urban areas
look like orange islands in a sea of green.
So what makes cities on the map
so much hotter than other areas?
Well, we built our cities in a way that traps heat.
Dark, impervious surfaces on streets and buildings
are really good at absorbing radiation
from the sun during the day and holding it in.
Buildings also form urban canyons,
which trap heat and block the natural airflow
that might otherwise cool a city down.
Cars, trucks, factories, and power plants
all release heat when they're running,
and their pollution can form a haze over the city
that causes a mini greenhouse gas effect
that stops heat from escaping.
Urban jungles also have fewer trees to provide shade
and fewer plants to keep things cool.
Okay, so here on this Sanitation Department parking lot
that's just covered in black asphalt,
the ground is registering at, what, 110 degrees Fahrenheit?
That's really hot.
Taking readings like this
is one way to make sure that what the satellites see
matches up with what's actually happening on the ground,
while also spotting things
that satellites can't detect from so far away.
It's what scientists call ground truthing.
- Is that satellite picking up the same thing
that we're seeing at the ground level?
And with the precision
that goes into building all these things,
yes, for the most part these satellites are very accurate.
- [Justine] That's Elizabeth Sebastian.
She developed a curriculum with NASA
to teach students about urban heat islands.
She taught us how to measure surface temperatures
using handheld thermal cameras
so we can better understand heat islands
that the satellites pick up.
- The reason why we want to use micro-size things
is to see those little pockets of heat
that are not gonna be captured by the satellite.
I want to see, well, where is it coming from exactly?
It could be a heat duct that's being let out from a building
or it could be something underground,
so it helps to kind of investigate a little bit further
on those really small-scale things.
- In cities, those little pockets of heat
can really add up and even be deadly.
Over the past three decades,
extreme heat has killed more people on average each year
than any other weather-related disaster in the U.S.,
and this pain isn't felt evenly.
In New York City between 2000 and 2012,
African Americans made up
about a quarter of the city's population,
but nearly half of its heat-related deaths.
That's part of a legacy of environmental racism.
Some spots in the city are actually hotter than others.
Where we are in East Harlem is one of them.
- Yeah, so we're coming up
on a really hot corner of East Harlem.
This is one of the areas where you find
really, really high temperatures on a very hot day.
- [Justine] Sonal Jessel took us on a tour
of some of the hottest parts of the neighborhood.
- In New York City, the heat vulnerability index,
which tells you sort of on a scale of one to five
how hot a neighborhood is,
or sort of its heat risk, East Harlem is a five.
It's because of a combination of built environment
and socioeconomic factors.
In terms of built environment,
we have that lack of green space,
major highways and sources of air pollution.
- [Justine] Another map might be able
to show us how this happened.
Starting in the 1930s,
financial institutions denied loans and home insurance
to people living in redlined neighborhoods.
These places were deemed hazardous,
often for having Black residents or other people of color.
And over time, the neighborhoods received less investment
for things like parks.
Instead, land was allotted for roadways
and industrial development.
- Because of redlining, there was also a lack of investment
in economic vitality, in businesses, in housing,
and over a long period of time, over many decades,
you see that that investment has not come back
into the community in the way that it was deserved.
- [Justine] After decades of systemic racism,
a person of color in the U.S.
on average lives in a census tract
that's nearly two degrees Fahrenheit hotter in the summer
than someone who is non-Hispanic white.
And formerly redlined neighborhoods
are up to 12 degrees Fahrenheit hotter
than other neighborhoods.
We're on this lovely, nicely-shaded street
in the Upper East Side.
Pretty fancy neighborhood in New York City.
Just a few blocks away, on the Upper East Side,
it's a different story.
Right here on the sidewalk,
that's a lot cooler than where we were just at.
There are more trees and parks,
and that makes this neighborhood
less vulnerable to extreme heat than East Harlem.
I mean, this is a cooler street. I can feel it.
It's nice and pleasant on the street,
not too hot.
Even on a sunny corner at a busy intersection,
we found that the surface temperatures
could be close to 25 degrees cooler than in nearby Harlem.
By our reading here on the black asphalt,
in the middle of the street, which should be really hot,
it's still significantly lower than where we were at
in East Harlem earlier.
So what can be done to cool East Harlem down?
Sonal has some ideas.
- Yeah, so the city has a good outline
for what they want to do
and they have done some really good things.
Really, what we want to see is just more of it.
- [Justine] New York has planted
6,000 more trees since 2018
and it's painted 10 million square feet of rooftops white
so that they reflect heat instead of absorbing it.
- We also need the city to be doing more
around investing in sustainable cooling options
for people's homes,
making sure people have cooling systems in their homes,
making sure lower-income housing
that's been poorly maintained gets the maintenance it needs
to be more efficient and better weatherized.
All of that needs to happen
in just a bigger way than the city is doing yet.
- [Justine] Researchers are using satellite remote sensing
to track progress that cities like New York are making
to counter the urban heat island effect.
Reggie Blake and Hamid Norouzi are doing just that.
- One of the research activities that we are working on
is to quantify how effective these mitigation efforts are.
In other words, we know that trees are helpful
to lower urban heat island,
but how much adding one tree to a street
will help to lower that urban heat?
- Not only are we looking at these adaptation measures
and seeing how effective they have been,
but also to use the latest technology,
the same thing we've been using, satellites,
to help us to understand
how impactful these trees have been.
- Measuring that progress will only become more important
as climate change makes the urban heat island effect worse.
One study estimates that there are already
around 600 heat-related deaths in New York City each year.
By 2080, that could climb up to 3,300 deaths annually
if nothing is done to tackle climate change.
While it doesn't solve the climate crisis,
better data can still be a tool
for people in heat-vulnerable communities
to move the pendulum in the other direction
- I think it's important to understand
the impacts that these studies have on the community
and how important it is to empower local residents
to become part of the revolution
of understanding what's happening in their neighborhoods
so they become part of the solution
and not part of the problem.
- Well, we built them in a way that traps heat. (laughs)
I'm yelling.
We're out here.
- [Shooter] It's like we're in a heat vortex.