12/23/2020 Can We Turn Down the Temperature on Urban Heat Islands? – Yale E360

https://e360.yale.edu/features/can-we-turn-down-the-temperature-on-urban-heat-islands 1/6

T

Yale Environment 360

Can We Turn Down the Temperature on Urban Heat Islands? Using citizen science volunteers, researchers are more accurately measuring temperature differences between city hot spots and their cooler surroundings. With heat waves intensifying, the results are now being used to

develop a range of innovative urban planning strategies.

BY J IM  MORRISON • SEPTEMBER   1 2 ,  201 9

he volunteers fanned out across cities from Boston to Honolulu this summer, with

inexpensive thermal monitors resembling tiny periscopes attached to their vehicles to

collect data on street-level temperatures. Signs on their cars announcing “Science Project in

Progress” explained their plodding pace — no more than 30 miles-per-hour to capture the dramatic

temperature differences from tree-shaded parks to sun-baked parking lots to skyscraper-dominated

downtowns.

�e work of these citizen scientists is part of a new way of studying the urban heat island effect, with

volunteers mapping two dozen cities worldwide in recent years. Past studies of urban heat islands — in

which metropolitan areas experience significantly higher temperatures than their surroundings — have

relied on satellite data that measures the temperature reflected off rooftops and streets. But Vivek

Shandas, a professor of urban studies and planning at Portland State University in Oregon and a

researcher leading the project, says the urban heat island effect is more complicated and subtler than

satellite data indicates.

“�ere’s much more nuance within the city,” Shandas says. “What we’re finding is that there’s upwards

of 15- to 20-degree Fahrenheit differences within a city. In fact, a city could have the same temperature

reading in one area as its rural or forested counterpart.”

On-the-ground data clearly demonstrate a correlation between lower-income neighborhoods and higher temperatures.

A Chicago resident struggles with triple-digit temperatures during a heat wave in 2012. AP PHOTO/M. SPENCER GREEN

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By understanding in detail where hot spots are located, cities can address extreme heat neighborhood-

by-neighborhood, choosing from a variety of strategies that include removing or whitewashing black

asphalt or roof surfaces, adding more trees for shade, requiring developers to vary the heights of new

buildings to increase airflow, and opening more public air-conditioned spaces.

Using Shandas’ research, Portland, the first city Shandas and his team surveyed, has proposed zoning

code amendments and strategies targeting urban heat, including limiting paved neighborhood

parking areas and increasing space for trees. In addition, city officials said that Shandas’ on-the-ground

data clearly demonstrated a correlation between lower-income neighborhoods and higher

temperatures. Shandas’ work also showed that the places where lower-income people often work, such

as the industrial areas along Portland’s rivers, also experience higher-than-average temperatures, the

officials said.

Other urban heat island studies have shown that the hottest places in metropolitan areas are often in

poor, minority neighborhoods with few trees, and this research can provide a framework for city

planners to address the problem.

Shandas and his teams have mapped 24 cities in

the United States and worldwide, including

Albuquerque; parts of the Vancouver

metropolitan area; Hong Kong; Doha, Qatar; and

Hermosillo, Mexico. In the past, urban heat

island studies relied on data from satellites or

stationary sensors, but Shandas’ appears to be

the first enlisting citizen scientists to collect

temperature data using mobile sensors.

Researchers have studied urban heat island

effects in every major country from Australia,

where a government study warned that heat

wave deaths would quadruple by 2050, to China,

which has more than 40 cities with populations

exceeding 2 million people. Globally, heat is the

number one weather-related killer, causing more

deaths each year than floods, tornadoes, or hurricanes. Extreme heat can kill directly via heat stroke

and indirectly through increased risk of heart attack and stroke. Climate models show that in some

cities the number of high-heat days could double by 2040.

�is summer’s heat wave in Europe, with temperatures soaring to a record-breaking 46 degrees Celsius

(115 degrees F) in the south of France, killed 1,500 people in France alone, the French health minister

said this week. Russian officials reported that a 2010 heat wave killed 11,000 people in Moscow. �e rise

in overall global temperature makes extreme heat events, including consecutive days of high heat,

more likely. Mitigating extreme heat, one recent study says, would save lives.

Urban heat islands have been generally understood since large cities began to emerge

in the 19th century, but research by Shandas and others reveals a complicated

patchwork of hot spots and cool spots that change during the course of a day and are

determined by urban design. Satellite data, for instance, showed midtown Manhattan

to be an afternoon hot spot. But mapping unveiled a different picture.

“When you actually go down to the ground, where people are walking and life is

happening, it turns out it’s not the same signal,” Shandas says.

“Ultimately, we’re trying to adapt the landscape to respond to the increasing frequency and intensity of heat waves,” says one

Researcher Vivek Shandas has mapped street-level temperatures in 24 cities worldwide.

COURTESY OF PORTLAND STATE UNIVERSITY

12/23/2020 Can We Turn Down the Temperature on Urban Heat Islands? – Yale E360

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expert.

�e long shadows of Manhattan skyscrapers, for example, can make parts of that borough cooler in

summer than some neighborhoods in Queens, which generally has low-rise buildings. On the other

hand, midtown Manhattan retains heat and starts the day much warmer because the heat that’s

absorbed by buildings, roofs, streets, and sidewalks during the day doesn’t dissipate as well at night.

“It’s the built environment that we’re really trying to understand because, ultimately, we’re trying to

adapt the landscape to respond to this increasing frequency, intensity, and duration of heat wave,”

Shandas says. “We’re trying to get more precise data. And there were so many surprises.” A large

expanse of water, for instance, or grass that is not watered, can be almost as hot as concrete, he says.

Jaime Madrigano, a researcher with the RAND Corporation who has studied urban heat, praised the

way Shandas and his colleagues were using citizen science volunteers and “getting the community

engaged in the issues around extreme heat… I think there are a lot of cities that are trying to make

these changes. �is kind of data is really important to doing that.”

Shandas grew up in Bangalore, and during visits there and to other cities in India he began thinking

about how cities have developed without regard for the increasing incidence of extreme weather

events linked to climate change, including heat waves. He began his research with a bit of engineering,

using a National Science Foundation grant to reach out to engineers who helped create the hand-made

instrumentation that transmits data. With funding from the U.S. National Oceanic and Atmospheric

Administration, he first mapped Portland in 2015.

A breakfast in Portland the next year with Jeremy

Hoffman, who had just accepted a job as the

climate and earth scientist at the Science

Museum of Virginia, led to a partnership and

citizen-science projects mapping Richmond,

Baltimore, and Washington, D.C.

�ose partnerships with local groups have been

invaluable, says Hoffman. “It was really useful to

have the local perspective” while creating the

mapping routes, Hoffman says. “Where is the

park that everybody goes to? Where are they

going to redevelop over the next couple of years?

�at kind of knowledge made our campaigns not

only scientifically useful, but publicly attractive.

It was the people themselves getting involved; it

wasn’t just the scientists.”

�e studies correlated data to the tenth of a

degree from sensors on vehicles that followed a

series of one-hour, zigzag routes — early morning,

mid-afternoon, and early evening — driven by

volunteers recruited by local science museums, universities, and non-profits. Fifteen teams mapped

Richmond during a summer weekend in 2017. One park along the James River measured 87 degrees F,

while a few miles away, along a four-lane roadway, it was 103 degrees.

Shandas and Hoffman say their work demonstrates that extreme heat is a social justice issue. In

Richmond’s hottest areas, they found a higher concentration of poverty and of 911 calls for heat-related

illnesses. Mapping last year in Washington, D.C. and Baltimore found a similar correlation, with

higher temperatures in lower-income neighborhoods largely barren of trees and lower temperatures in

more affluent, tree-shaded areas. Shandas and Hoffman recently completed a paper, due to be

published soon, comparing redlined neighborhoods — those once illegally designated by lenders as

A mobile sensor collects temperature data in suburban Sacramento this summer. COURTESY OF

VIVEK SHANDAS

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too risky to make home loans — with extreme urban temperatures. “�e big take-home point for the

paper is that 92 percent of the cities that were redlined are now warmer than their A-rated neighbors,”

Hoffman says. “�is seems like it’s predominantly due to a lack of green and a dominance of gray.”

Shandas says the research has uncovered six things that affect urban heat. �ree are living — the

volume of the tree canopy, the height of the tree canopy, and the ground level vegetation. �ree are

human-built — the volume of buildings, the difference in building heights, and the coloring of the

buildings.

The differences in morning and afternoon temperatures in Richmond, Virginia. COURTESY OF JEREMY HOFFMAN

Poverty levels in Richmond. Lower-income neighborhoods often experience the worst heat in the city. COURTESY OF JEREMY

HOFFMAN

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�ere were some surprises, he says. �e volume of buildings can have both a negative and positive

effect. Tall buildings that cast shade lower relative afternoon temperatures, while a large volume of

shorter buildings, like the big-box stores in suburban areas, help generate hotter afternoon

temperatures. Ground-level vegetation doesn’t necessarily reduce temperature — it’s not that much

cooler than asphalt — unless it’s watered. Shandas also has found that increasing the difference in

building heights in an area creates more air circulation, which has a cooling effect.

Creating cooler cities doesn’t necessarily mean building at lower densities. What matters, he says, is

varying building heights, the canopy cover, and street widths. “It wasn’t about no buildings and all

green,” he says. “It was about designing our spaces more thoughtfully.”

Some cities are already using the detailed research to guide decisions. In Richmond, a heat map and a

vulnerability map showing those more at risk appear in reports for housing, transportation, and the

climate action plan, and the city’s comprehensive master plan calls for reducing urban heat.

Richmond hasn’t invested in planting trees yet, he adds, but citizen-science groups like Groundwork

RVA and the museum have developed programs such as �rowing Shade in RVA, a program teaching

students about urban heat that has led to them planting peach trees at local high schools and

designing shady structures for neighborhood bus stops.

Some of the deadliest heat waves in recent decades have taken place in northern cities, where people are not accustomed to

extreme heat.

Groundwork RVA’s parent organization, Groundwork USA, has funding to expand on this work for a

Climate Safe Neighborhoods project exploring the relationship between historical race-based housing

segregation and the impacts of climate change in Denver, Colorado; Elizabeth, New Jersey; Richmond,

California; and Pawtucket, Rhode Island.

Even at higher latitudes, heat is an issue. According to the Centers for Disease Control, some of the

deadliest heat waves in recent decades have taken place in northern cities like Chicago, where people

are not accustomed to extreme heat and more residences lack air conditioning. A five-day heat wave in

Chicago in 1995 led to the deaths of 739 people.

In Portland, Shandas has created heat maps containing demographic information including age, race,

education, poverty level, and education. �e city is focusing its efforts in areas where urban heat

islands and indicators of vulnerability, including low-income levels, overlap. Shandas’ work is reflected

in Portland’s Better Housing by Design zoning update, in which the city has proposed zoning

amendments to reduce urban heat island effects, including limiting surface parking areas in

residential neighborhoods and requiring landscaped setbacks between buildings and streets to

provide more space for trees.

His next step is to expand heat island mapping to 50 cities in 2020. �e key question,

he says, is whether cities will begin making the changes necessary to decrease deaths

from extreme heat.

“�ose are very preventable deaths,” Shandas says. “We can identify those locations

and ameliorate some of the effects. It ultimately comes down to how to help these

people. We have the technology.

Jim Morrison writes about the environment, travel, the arts, and business. His stories have appeared in Smithsonian, �e New York Times, �e Wall Street Journal, National Wildlife, Pacific Standard, �e Washington Post, and numerous other publications. He lives in Norfolk, Virginia.  MORE  →

11/4/2020 The long distance harm done by wildfires – BBC Future

https://www.bbc.com/future/article/20200821-how-wildfire-pollution-may-be-harming-your-health#:~:text=But the longer-term impact,legacy carbon%2C” says Flannigan. 1/6

ENVIRONMENT

The long distance harm done by wildfires

(Image credit: AFP/Getty Images)

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By Allison Hirschlag 23rd August 2020

Smoke from burning forests and peat can linger in the atmosphere for weeks, travelling thousands of miles and harming the health of populations living far away.

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rom far above, they almost look beautiful. Golden yellow tendrils etched across the dark forest landscape below. But in daylight, at close range, the devastation wrought by the fires in the Krasnoyarsk region of Siberia is harrowing.

A wall of blistering flames engulfs the vegetation. Behind it, charred trees stand like blackened toothpicks while columns of smoke choke the air, rising high up into the atmosphere. Since the start of 2020, Russia has seen an estimated 19 million hectares (73,359 square miles) consumed by wildfires, according to Greenpeace International’s analysis of satellite images. Nasa has warned that abnormally warm temperatures in eastern Siberia – particularly in the Sakha Republic, more than 1,250 miles (2,000km) away from Krasnoyarsk – have led to more intense and widespread fires than normal.

The destruction this leads to is undeniable. Swathes of forest and peatland are destroyed. Countless animals caught up in the flames and smoke perish. And when the flames reach areas inhabited by people, they can claim many lives and homes of those unlucky enough to be caught in their path.

In the first few months of 2020, Australia grappled with the worst wildfire season in its history. It claimed the lives of 33 people, destroyed thousands of homes and saw 18 illi h t (69 500 il ) b d Th billi i l kill d

The health risks of wildfire smoke

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