The city of São Paulo began last year with a detailed map of the population's risk to extreme heat, which combines environmental conditions and socioeconomic aspects to identify areas of greatest danger, exposure, and vulnerability.
The map was produced by Denise Duarte, professor at the School of Architecture and Urbanism (FAU) at the University of São Paulo (USP), with the researcher Luiza Muñoz, who developed the work in her doctorate at FAU-USP, and Professor Rohinton Emmanuel, from the University of Caledonia in Glasgow, Scotland. The main results were published in September 2025 in the journal Urban Climate.
The researchers cross-referenced satellite images and environmental indicators with socioeconomic characteristics, such as income, age, and housing conditions. Data from the 2022 Census allowed them to analyze each of the 27,592 census sectors where the Brazilian Institute of Geography and Statistics (IBGE) divides São Paulo.
The conclusion is that the risk of extreme heat is higher in the peripheral areas of the capital, with greater population density and lower-income residents. "This is the most affected population, the one that can die from the heat," says Duarte.
In this interview, she discusses strategies to reduce the risks of heatwaves and argues that evidence as gathered in the map should guide the priorities of climate change adaptation policies.
The researcher coordinates projects funded by FAPESP on city resilience and adaptation, focusing on nature-based solutions, and as author, she has contributed to the development of the Special Report on Climate Change and Cities (SRCities), the Seventh Assessment Report (AR7), and the Intergovernmental Panel on Climate Change (IPCC).
How does the map you created differ from other similar surveys?
By cross-referencing environmental data with socioeconomic information in each of the census sectors of the city of São Paulo, we achieve greater refinement. Other surveys are more general, by large regions, for example. With Census data, it is possible to reach a more detailed scale to make simulations about the effects of climate change and the policies adopted to face them.
Since we work with open data, the map can be updated at any time if new information emerges or when there is a new Census. Our methodology is also available, and other cities can replicate it to create their own risk maps.
What does the São Paulo map reveal?
We found that the risks are a reflection of our inequalities. People living in peripheral areas, with higher population density, such as favelas, are exposed to greater risks than those affecting residents of other regions of the city. This reflects not only housing conditions but also other economic aspects, such as people's income.
In European countries, where inequalities are smaller, age is the factor that most influences people's vulnerability. In São Paulo, not, because most elderly people live in more central neighborhoods, in more favorable conditions to adapt to the risks created by heatwaves. In the favelas, where the risk is greater, the population is younger and there are many children.
The proximity of parks and green areas helps reduce risks, but our map shows that this does not always happen when considering other factors. In the periphery, many people live miles away from the nearest park. Many parks have few trees and little shade, as well as deficient infrastructure to receive the population.
How has the public power responded to this evidence?
The map can help define priorities, and we have already exposed our work to members of the municipal administration several times. In 2023, when we had very strong heatwaves, the city hall began to implement emergency plans, with the High Temperatures Operation, offering water, fruit, and shade in tents erected in some parts of the city. These actions seem insufficient to us.
With the data from the map, we can have structural actions for adaptation to extreme heat. We could create true urban oases along mobility axes, taking advantage of the structure of bus and subway terminals, parks, schools, and sports centers as support points to expand the reach of this type of emergency action.
Residents of the periphery spend hours a day commuting. Many work exposed to the heat on the streets, without shelter. It is a human anthill subject to risks permanently. Such a strategy could multiply the shelter points during the most intense heat periods.
What else could be done?
We must seek a strategy compatible with our reality. In Europe, they are using libraries, community centers, and other buildings with air conditioning to create a network of urban refuges. We do not have as many libraries as they do, but we have many schools and sports centers that could be used as shelters during an extreme heatwave.
The way out for adapting to climate change cannot depend only on air conditioning units. We need to use existing structures and transform them into places where people can cool down, hydrate, and receive care if they feel unwell.
The City Hall says that green areas cover half of São Paulo, but this count includes vacant lots and golf courses, as well as other green areas inaccessible to the population. Most do not have adequate vegetation or structure to receive the population. Our map shows this clearly, and as tree planting is also unequal.
The use of air conditioning units has grown in buses, trains, and commercial and residential buildings. Why is it not enough?
They are obviously essential in some places, such as hospitals. But one cannot simply "air-condition" a city like São Paulo. Imagine the impact of this on energy consumption. Air conditioning can be part of the solution, but there is much to do with passive conditioning, vegetation, and other nature-based solutions.
Not all buses have air conditioning, and even those that do do not always have up-to-date maintenance. Overcrowding on long routes and the precariousness of bus stops also increase people's exposure during a heatwave. We still have in São Paulo bus stops covered with glass, without shade, which is absurd.
Some office buildings need to be evacuated if the air conditioning does not work, or if there is a power outage. They do not have a plan B for operation because the facade is entirely glass and the windows are sealed. They are like closed glass boxes that absorb solar radiation and trap the heat inside. It is impossible to imagine that this is the only way out.
A tool built collectively to strengthen the response to the climate crisis and reduce risks with the community. It is part of a set of 12 plans that contributed to the design of an innovative public policy, formulated by the Risk Mitigation and Prevention Department of the National Peripheries Secretariat (SNP), of the Ministry of Cities.
Are there studies on the impact of climate change on the periphery missing?
I participated in a group of researchers who developed an adaptation plan for Jardim Colombo, in the Paraisópolis complex. We first conducted a literature review and then a risk, problems, and solutions survey, based on interviews and meetings with community members. The project was presented to the Ministry of Cities.
One of the things we verified is that for informal settlements like this one, there are many studies on floods, floods, and landslides, but very little on heat. Among the residents, the risks associated with extreme heat seem to be less perceived than those caused by floods. They are aware of the lack of ventilation in the house on the hottest days, but floods and landslides are more evident threats to them. Perhaps this will change with the repercussions of events like the heatwave that affected Europeans this year.
In São Paulo, there is a notable initiative from the Municipal Secretariat of Green and Environment, the Sampa Adapta program, in technical cooperation with the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) at USP. The secretariat managed to obtain resources from Vital Strategies, an international organization that supports health policies, and acquired 25 temperature and humidity sensors, which we installed in five neighborhoods of the city. Residents of the communities themselves received some of the instruments and were responsible for taking care of them after installation. With the sensors, we will have local measurements of temperature and humidity in vulnerable areas.
Are there enough data to build risk maps in other Brazilian cities?
In São Paulo, we have an advantage, which is GeoSampa, a platform that brings together a large amount of georeferenced data. It is thanks to it that we can make cross-references like those that allowed the construction of the risk map. Other capitals, such as Rio de Janeiro and Belo Horizonte, also have digital maps, but they do not have the same amount of data in a single platform.
Residents of the periphery spend hours in traffic. Many work exposed to the heat on the streets. It is a human anthill exposed to risks permanently.
Are there examples of effective climate adaptation policies in other Brazilian capitals?
Rio de Janeiro adopted a protocol to deal with extreme heat situations. Following what occurred during the Taylor Swift show in 2023, when a girl fell ill and died due to excessive heat, state law 10.557/24 was approved, which obliges event promoters to provide water free of charge to spectators. And the city hall adopted a protocol to be followed if the temperature exceeds certain limits, with an alert system, water supply, and other measures. There are restrictions for events and outdoor activities if temperatures above 40 °C are recorded for three consecutive days.
Your training involved engineering, music, and architecture. How did this path lead you to the study of urban climate?
I am from Mato Grosso, from Cuiabá. There was no architecture course in the state when I entered university, so I did civil engineering and, as soon as I finished, I went to the School of Engineering of São Carlos, USP, which had an architecture department. I also studied music, due to my mother's influence, who is a pianist. I played piano, but I stopped decades ago.
The City Hall says that green areas cover half of São Paulo, but this count includes vacant lots and golf courses inaccessible to the population.
During my master's in São Carlos (SP), I took the architecture courses that I did not have in my undergraduate degree and studied environmental comfort in buildings built in Cuiabá. In my doctorate, at FAU-USP, I examined how different ways of land use affect urban microclimates. Since it is an interdisciplinary topic, I became closer to other areas important for studying it at USP, such as meteorology and geography.
27,592 census sectors of São Paulo to build the extreme heat risk map
According to the city's protocol, 40 °C for 3 consecutive days is the limit that triggers restrictions on outdoor events in Rio de Janeiro
Why did you choose the climate issue as the focus of your research?
In 2010, I was invited to participate in a multidisciplinary Project from FAPESP on the impact of climate change, coordinated by Fábio Gonçalves, from IAG. Our group analyzed the thermal comfort of the elderly and suggested architectural changes that would help them cope with the heat. When I started studying the IPCC reports, I realized the gravity of the problem.
I decided to work for this cause for the rest of my academic career. I realized that architecture and urbanism had an important contribution to make and began to direct my projects on urban microclimates, vegetation, and densification to this interdisciplinary field.
Have architecture courses incorporated this interdisciplinary effort?
In the postgraduate program at FAU-USP, I work in the area of architectural technology. We have three subjects focused on climate change. The oldest one deals with environmental comfort in streets, sidewalks, and other open spaces and was reformulated over time. I created two more, with my colleague Leonardo Monteiro. One expands the scale to look at cities as a whole. In the other, we studied the impact on buildings—not only from the climate crisis but also from the energy and sanitary crisis, due to the Covid-19 pandemic.
These subjects have attracted students from other fields. We have a very strong interaction with researchers from biological sciences, public health, engineering, and meteorology. There is no sense in restricting the study of these topics to architectural and urban aspects, without partnerships with the other areas. We have also brought this to undergraduate studies.
Are new constructions being designed to face a scenario of higher temperatures?
Do you know the flyers distributed on the streets when new properties are launched? They are all the same, basically the same plan, because municipal codes regulate nothing, and the real estate market dictates the rules. There is no concern for thermal issues and adaptation. They are encouraging the construction of glass boxes, with false balconies, areas reserved for air conditioning condensers, and sealed windows. I have never seen such bad plans as now.