Data Dive: Heat Mapping New York City, and Environmental Justice
Data DivesThese conversations are with Columbia Climate School researchers to find out more about their work, and to explore trending topics through data science and visualization.
The Scientists
Liv Yoon‘s research is at the intersection of climate change, social inequities, and health, with a focus on community engagement work. As a social scientist, and a postdoctoral scholar at Columbia Climate School she views climate change in terms of a sociopolitical problem. Her research focuses upon climate change as an opportunity to challenge and promote structural changes to alleviate the social inequalities which both contribute to and are exacerbated to the climate crisis.
Joey WilliamsHe directs the operations of CAPA Heat Watch, which provides detailed descriptions of urban heat using a coordinated data-collection campaign. He combines his skills as an engineer in process design with his passion for environmental and human health to help the CAPA group improve climate resilience efforts across the US. He graduated from Portland State University with a Masters in Urban and Regional Planning. He was also a graduate assistant in the Sustaining Urban Places Research Lab. He enjoys running, backpacking and creating new recipes.
The Project
The New York City heat map project is part a National initiative. Williams’ team produced the heat map data shown in the map below using data collected by citizen scientists; Yoon is the principal investigator in the New York City initiative. The interview below focuses on how the heat map was created and what it tells us about historical racism as well as current social inequalities.
Data
Heat Map, Northern Manhattan and South Bronx. Afternoon, 7-24-2021
Afternoon on July 24, 2021 Blue tones signify cooler temperatures than average, while reds indicate warmer temperatures. Heat Data: CAPA Strategies [view data and final report]. Basemap: Esri. HERE. Garmin. Intermap. Inc. P Corp. GEBCO, USGS. FAO. NRCAN. GeoBase. IGN. Kadaster NL. Ordnance Survey. Esri Japan. METI. Esri China. (Hong Kong). (c). OpenStreetMap contributors and the GIS User Community.
The Dive
How was the research project organized? What data was collected? How were these raw data prepared for further analysis and analysis?
Joey WilliamsUsing simple-to-use sensors, community scientists collect readings on air temperature and relative humidity [pdf]These sensors attach quickly to bicycles and passenger cars. The sensors automatically take measurements every 1 second, which is equivalent to thousands of data points collected over the course of a one-hour-long trip. The sensors also record latitude, longitude, time and speed, allowing CAPA’s data scientists to pinpoint the location of each measurement along with important meta-data that help to filter out outliers and other anomalies from the raw dataset. Our community scientists collect field notes to validate the data and identify interruptions to the experiment such as inclement weather.
Afternoon heat mapping measurements for the South Bronx. Red shading indicates higher temperatures than the average.
How can high-resolution satellite imagery be used to describe the land use and cover around each data point? How can this data be used to inform the final heatmap?
Joey Williams: In order to model ambient heat across an entire study area, CAPA’s method draws on the relationship between air temperature and the thermal properties of the urban environment. For example, asphalt and concrete absorb and retain heat while areas that are shaded reduce air temperatures. Satellite imagery from the Sentinel-2 satellite constellationThis allows you to describe the land and its material properties in multiple spectral wavelengths or bands. It is done in 10 x10 meter square cells. The land variables are combined with thousands of ambient measurements from community scientists to create a machine-learning model that predicts heat across the entire study area.
What makes CAPA’s urban heat mapping approach different from other methods?
Joey Williams: CAPA’s approach to mapping urban heat is unique in several ways. This approach describes the heat we feel at the human level, which is roughly one-to two meters above the ground. The most common method of mapping urban heat is to use satellites to measure the temperature of surfaces. This is known as land-surface thermometry or LST. Second, the high resolution of CAPA’s maps allow for a more fine-grained approach to understanding the distribution of heat block to block, whereas typical LST methods provide more coarse descriptions such as at the neighborhood scale. Lastly, CAPA’s heat mapping program, Heat Watch, engages local community members and stakeholders in a process of co-creation, adding a helpful degree of ‘civic legitimacy’ to the data and models. The campaign helps community members to understand the climate risks in their area and what they can do to mitigate them.
What is the first thing that comes to your mind as a social scientist when looking at the final heatmap? What stories, past and future, does it tell you?
Liv Yoon: My first reaction upon seeing the resulting maps was that I wasn’t surprised. The data confirmed satellite imagery and previous research that showed that northern Manhattan and South Bronx were hotter than other areas in our study area. But I also saw legacies from the past in heat distribution and related disparities. The image below shows our heat map overlayed on a historical map showing redlining in northern Manhattan. The 1938 redlining map is a ‘residential security map’ from the Home Owners’ Loan Corporation where areas deemed ‘high-risk’ are shown in red. These were essentially Black communities, which were denied mortgage credit. To this dayThese areas, which were previously marginalized by race and class, are still marginalized. Resources, including green spaces, are often not available to the underserved.
Composite: Redlining and Heat Maps for Northern Manhattan
Use the slider to adjust heatmap opacity. The heat map has been modified to approximate historical redlining map areas. Redlining Map Mapping Inequality
What WasSurprisingly, parts of the Upper East Side were as hot or even hotter than areas in northern Manhattan. But it’s important to remember that populations in higher income areas are more likely to have better buffers against extreme heat, such as air conditioning, working indoors in climate-controlled offices, and access to consistent, and good quality health care.
How could the heatmap data be extended? Or combined with other information to provide new insights? What questions are left to be answered?
Liv Yoon: Our project aimed to show which parts of the city were more hot than just showing which. We also presented heat data with other maps that illustrate social inequalities. We want to link the dots between extreme heat and social inequities. This is all within the larger context of climate change as a threat multiplier. Take, for instance, the overlap with this map that shows the median household income in the city.
Map: Median Household Income 2017, 2017. Source: Social Explorer
It’s no coincidence that the hotter parts of the city also happen to have lower incomes. This shows that people living in these areas are less likely have adequate air conditioning or good quality care.
These areas also have higher rates of chronic diseases like hypertension and diabetes. which increase one’s chance of developing a heat-related illness.
Map: Average 5-Year Annual Heat Stress Hospitalizations. Age-Adjusted Rate
Data: NYC Environment & Health Data Portal
It’s important to remember that residents of these areas are not ‘biologically wired’ to be more susceptible to these diseases. As with many other health conditions, there are also social and environmental determinants. For example, poorer quality food and lower quality health care. Weathering EffectThe idea that stress manifests physiologically in disadvantaged populations, and that disadvantaged people are more likely to feel it, is one of the social determinants that could cause such stark overlaps.
Poor air quality, another environmental problem commonly found in low-income communities, can also increase the heat’s impact. Poor air quality is a chronic problem in the South Bronx, and particularly in the Mott Haven-Port Morris area, which is known as ‘Asthma Alley‘ due to having one of the highest childhood asthma rates in the country.
Map: Asthma Emergency Department Visits, Children 5-17 Years Old
2018 Estimated Annual Rate (per 10,000 inhabitants). Source: NYC Environment & Health Data Portal
High traffic, polluting industries and a lack green space all contribute to the problem. poor air qualityThese are the most common areas. Asthma flare-ups can be exacerbated by high heat, smog, and poor air quality.
It is also evident that the green spaces in these areas, which are hotter and have lower incomes, are smaller.
Map: Tree canopy coverage percentage
Data: NYC Environment & Health Data Portal
The COVID-19 pandemic highlighted the complexities and consequences of a lack green space. The public was advised to seek shelter from the virus outside as soon as possible and to maintain their mental and physical health. But Healthy green spaces were not an option in the Mott Harbour-Port Morris regionIn these areas, the outdoors is merely industry and waste transfer facilities. There are no highways. Even more so when extreme heat is added to the mix.
One question remains is what the nature of extreme is. indoor heat. For instance, residents of these areas told us that their homes retain heat from the day, so they don’t get relief even at night when the air outdoors cools down. This can cause poor sleep and fatigue which impacts one’s overall health and well-being. Although indoor heat was not within the scope of this project, organizations such as WEACT has been working closely with community members on this matter.
How can this data be used to make a difference in communities? What are the next steps in this process?
Liv YoonBelow are some initiatives that were created through consultation with South Bronx Unite
- An online story map is being created that links extreme heat, social inequality, and health, all within the context of climate change as a threat multiplier and growing urban populations. We plan to include maps of different social indices, such as demographic data, health disparities data and other relevant socio-environmental factors to show the connections and overlaps. We aim to have this completed before the heatwaves in this summer.
- Christian Braneon and I are both co-investigators on this project. New York City Panel on Climate Change(Christian is cochair. The group is currently working on its fourth evaluation so that the latest granular data can be integrated into the report.
- In collaboration with NYC Department of Health and Mental Hygiene, we hope that our data can contribute to bolstering the city’s efforts at combating heat-related disparities. Our street-by-street granular data, for example, can be used to help the city find additional cooling centers or green areas in most affected areas. This could also allow the city to implement programs such as free air conditioning for those who are most at risk.
- South Bronx Unite advocates for more green and blue space within their neighborhood. They intend to use the data to push for more green space in their neighborhood. Their efforts were greatly appreciated..
More information about the project: Study Maps Urban Heat Islands with a Focus on Environmental Justice
More on CAPA’s heat mapping methodology: For predicting extreme urban heat locations, satellite and ground measurements can be combined
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