Natalia Chi
In any discussion of the devastating effects of climate change, one fact often slips through the cracks. It means that targeted interventions can reduce the potentially lethal heat exposure of urban dwellers not only in the years to come, but also for those living in the present.
Examples can be as simple as painting the roof white to reflect the sun or adding a bus shelter to provide shade for commuters. Some require ongoing care, such as making sure newly planted trees stay healthy. Every city and community is different, so there is no one-size-fits-all solution, experts told the Tribune. But there is a universal starting point. That is to identify areas where the temperature rises frequently. Hottest.
[ Read the investigation on disparities in Chicago’s summer heat ]
Knowing if local temperatures are trending higher can make a difference, especially for people who are sensitive to heat stress, including children. Elderly people, athletes, low-income people, pregnant women, people with certain medical conditions Or work outdoors. We are making this information accessible to other cities as well. But Chicago was not.
In identifying the hottest areas in Chicago, the Tribune found that data from regular temperature sensors on the ground, such as those at O’Hare and Midway airports, didn’t paint the full picture. Temperatures can vary from community to community and sometimes from block to block.
Tribune reporter Sarah McCareg first learned about remote sensing data, or observations of the Earth collected by satellites, when she previously traveled to areas with inadequate air quality monitoring stations. But until the Tribune changed its mind, extracting temperature data and other information from U.S. Geological Survey satellite imagery proved difficult. Google Earth engine.
Google Earth Engine, a little-known Google portal outside of climate research circles, allows users to use JavaScript or Python to filter data about their environment by specific criteria or location. In addition to using programming languages, calculations can also be performed through Google servers, which have much higher processing power than regular computers.
After consulting Google Earth Engine’s code library and scientific research, and reviewing best practices for using filters to obtain the highest quality data, Tribune used Google Earth Engine to develop Landsat-8 and Landsat- We collected ground temperature data from 9 satellites. It orbits about 500 miles above the Earth’s surface and passes over the same location every 16 days.
Unlike the daily measurements from the MODIS satellite, which are also often used in heat mapping, the Landsat satellite collects observations in smaller increments (30m x 30m area), which are suitable for accounting for community-level differences. to collect Tribune used Google Earth Engine to match measurements taken from these areas to census block groups and convert measurements from Celsius to Fahrenheit.
Clouds affect the accuracy of remote sensing data, so this analysis was performed with minimal cloud cover from 2013, when Landsat-8 data first became available, to the end of August 2022, when Landsat-9 appeared. It was based only on observations collected on subdued summer days. was also collecting data. In accordance with standard scientific practice, certain data points cataloged by the USGS as ‘clouds’ or ‘cloud shadows’ were omitted along with data points marked ‘water’.
The Tribune’s analysis was based on deciles of mean temperature. Deciles of mean temperature are 10-step measurements that show how values relate to each other. For example, the 10th decile represents a block group that is cooler than 90% of the rest of Chicago. Race and ethnicity are also considered. , poverty, household and health data from the US Census. Data tables were joined and analyzed using Structured Query Language.
The Tribune then created its first maps in ArcGIS and began using it to help residents in historically hot areas, locating field reports during last summer’s heat advisory. . Former Tribune reporter Stephanie Casanova and Tribune photographer E. Jason Wambusgans worked with McCareg for this report.
[ Mapping a threat: How climate change may deepen heat disparities in Chicago ]
Because exposure to extreme heat can exacerbate the health effects of air pollution and vice versa, the Tribune also analyzed the Chicago Public Health Department’s Air Quality and Health Index. This index provides a good picture of air pollution in approximately 2,170 block groups that provide percentile measurements of air quality as of 2020. data.
To better understand the allocation of some cooling resources, the Tribune used data from the Chicago Transit Authority and the city to determine the locations of bus stops operating in the city as of March 2022 and I’ve identified the locations of bus stops in Chicago as of March. October 2021. Pursuant to the state’s Freedom of Information Act, Tribune requested an update to bus stop and bus stop location data in April, but CTA did not provide it. Locations and areas of public parks in Chicago were also merged in ArcGIS, combining the locations of park centers into their corresponding block groups to estimate the distribution by decile.
To further refine, validate and visualize data analysis, Tribune has partnered with: Climate and Health Center at Boston Universitythe researchers also added an analysis of access to cooling resources in Chicago’s most vulnerable communities, which have the highest average surface temperatures.
Muskaan Kemani, a researcher who created a thermal map of Wichita, Kansas as part of his NASA internship, made a new analysis of the data in Google Earth Engine, adding observations cataloged as clouds and cloud shadows. to remove observations collected within 1 km of water depth. Or water. Using the programming language R, Kemani analyzed average summer surface temperatures by block group and found the same disparities as the Tribune.
The final analysis of surface temperature was performed using 35 images from the Landsat-8 and Landsat-9 satellites collected on days with less than 20% cloud cover from June 1 to August 31, 2013 to 2022. Based on census every 5 years. Estimates from the 2021 American Community Survey.
Of course, the temperature doesn’t exactly match the block group boundaries. But Kemani said it is important to map thermal differences within recognizable boundaries to help allocate resources. “This allows us to see variations in surface temperature, whose spatial units correspond to what is real and tangible for decision makers.”
Experts speaking to the Tribune made an important caveat about surface temperatures. That is, the surface temperature is not the same as the temperature readings you see in weather forecasts. As Chicagoans accustomed to scorching sidewalks in summer know intuitively, surface temperatures are more extreme, hotter when it’s hot and cooler when it’s cold. “It’s not as accurate or accurate as a ground station, just because it’s measuring something that isn’t exactly temperature (of air). But it does give you a spatial pattern,” he said, participating in the analysis. Not Illinois climatologist Trent Ford spoke about remote sensing.
Kemani calls Google Earth Engine a “game changer” that shouldn’t be viewed solely as a full-time researcher’s domain. “10 to 20 years ago this was not possible because there was no way to download as many images as we are using today. It’s a valuable tool,” she said. “So many people and organizations are now able to perform this kind of analysis.”
For those not interested in learning the coding skills needed to take advantage of Google Earth Engine, Boston University researcher Jason Randle has found a population that can reveal insights without extensive analysis. , said there is a wealth of other health and environmental data. For example, the Centers for Disease Control and Prevention’s Social Vulnerability Index reflects a combination of measures such as race, poverty status, and disability at the census area level.
“Importantly, we don’t store documented scientific research in this box that says only a certain type of person can do it, or that this much degree needs to be obtained,” he said. Mr Randle said. “Just looking at the data in your own neighborhood is helpful, and you’ll learn a lot of things you didn’t know before.” You can access these identities by searching the interactive map and clicking on the details displayed.
Randle cites the CDC’s Vulnerability Index and the location of all public cooling facilities promoted by the City of Chicago (from the city’s six official cooling centers to park districts, police stations, and advertised during heat advisories). to the library location) were combined to analyze the surface temperature. Randle used network analysis tools in ArcGIS to identify a number of areas within a half-mile walk that had the highest social vulnerability ratings, the highest surface temperatures, and no public air conditioning.
[ Visit the Chicago data dashboard created by Boston University’s Center for Climate and Health ]
Both he and Kemani said they hoped other researchers and journalists would pursue similar partnerships in the future to delve deeper into the regional dimensions of the climate crisis. Partnering with journalists can make climate science more accessible to the general public, they said. Partnering with scientists can enhance the intensity of journalists’ analytical work and provide organizational resources that newsrooms may lack to host and visualize large datasets. increase.
The Tribune attended an online City Hall meeting on the city’s climate change plan and reviewed the city’s data on green roof permits, while several experts underscored the importance of local preferences in determining interventions. , surveyed community efforts to identify residents who were already trying solutions in their neighbourhood.
“It doesn’t necessarily have to be an apocalyptic scenario like this,” Randle said of the climate crisis message. “There is hope and there are people learning how to thrive in the midst of things like this.”
