Heat islands indicate effects of urbanization

Study detected variation of up to 6,7 ºC between nearby areas located in Indaiatuba

Heat islands indicate effects of urbanization

Study detected variation of up to 6,7 ºC between nearby areas located in Indaiatuba

Just 3,7 km apart, two locations in the city of Indaiatuba (SP) showed a temperature difference of 6,7 ºC. This was one of the data presented in Larissa Zezzo's doctorate, defended at the Institute of Geosciences (IG) at Unicamp. The urban heat island (UHI) phenomenon, an area with higher temperatures when compared to rural areas, occurred more intensely in winter, the driest season of the year in the region. 

The data, collected at ten points in the city, refer to 2022. Between May and July, the magnitude of the ICUs was extreme at point 6 (urban) compared to point 2 (rural), being equal to or above 6 ºC (6 ºC, 6,7 ºC and 6,2 ºC). The reasons, according to Zezzo, an environmental scientist and now a PhD in science, are associated with the characteristics of the season, in which there is greater atmospheric stability, environmental factors, land use and land cover, and urban factors. “These factors together generated such a high magnitude. On at least 10% of the days in July, there were extremely large magnitudes of heat islands, when we compare the two points.”

Research indicates that heat islands occur more frequently at night. “There are different rates of heat absorption and release, depending on the construction material. Concrete, for example, makes the wall feel warmer, sometimes, at the end of the day. That wall will probably remain warm until the evening, around 21 p.m., when heat islands are most noticeable,” explains the researcher. In places where there is more vegetation and other types of construction materials, there is less heat retention.

Professor Priscila Coltri, thesis advisor and director of the Center for Meteorological and Climate Research Applied to Agriculture (Cepagri) at Unicamp, stated that the study fills a gap in data related to UHIs in small and medium-sized cities with tropical climates. Research on the phenomenon predominantly deals with large cities located in temperate climate regions. “Medium-sized cities ended up without data to support any type of response. So the study shows that just because the city is medium-sized or small does not mean that the magnitude [of UHIs] is not as intense,” she said.

an alert

The study on heat islands was published in the journal Environmental Monitoring and Assessment. The author of the study now warns that the place where the lowest temperature was recorded in the analyzed area is a region in which Indaiatuba is expanding. “Therefore, the warning is: if the vegetation is removed to make way for housing, this will possibly be a place where the temperature will increase. This is a key issue for the government to think about mitigation and adaptation measures, how to restructure the city and, mainly, plan, considering that Indaiatuba has been growing and is expanding peripherally.”

Coltri highlights the importance of green areas in efforts to mitigate the phenomenon of heat islands. “In places where there is a greater quantity of green areas, the temperature ends up being lower. This data can support planning aimed at these areas in cities, because the less green area we have, the more intense the heat islands become. But green areas are not just in the sense of planting a few trees on the street. They are large green areas, squares, parks and large gardens. And not only in the city but also in its surroundings.”

Low cost

Indaiatuba was chosen for the study because it is a city that has been experiencing rapid development in recent years. However, there was a challenge to be overcome when it came to obtaining the data. “The problem is that Indaiatuba only has one official meteorological station, which is not enough to map the entire region. At least ten sensors and ten shelters [for the sensors] would be needed,” said the researcher.

At the time, each sensor/shelter pair would cost around R$1.500, which was too high. Therefore, the researchers developed and validated a low-cost shelter with the help of Marcelo Soeira, a PhD student in environment and society at Unicamp. Built with affordable materials, such as pine slats and polypropylene (PP) and polyvinyl chloride (PVC) plastic, the shelter followed the guidelines of the World Meteorological Organization (WMO). 

Professor Coltri’s students also helped develop the equipment. Fernanda Pestana, for example, collaborated in the field monitoring and data checking phase. In her scientific initiation, Pestana uses data collected in a study on socioeconomic factors and climate. “We know how difficult it is to obtain this data. So, when we can add other perspectives to an ongoing research project, it’s very good,” she commented.

When describing her experience of going into the field and interacting with residents of the areas studied, the student commented on the importance of providing feedback to the community regarding the research. “In general, we don’t have much of a perspective, in the place where we live, on what the difference is between urban and rural areas. And this type of research makes the conditions in which we live very clear,” she observed. 

Education and communication

Communication and education about climate change were also among the topics covered in Zezzo’s doctorate. “It is noticeable that when you are in a greener area, the temperature is more pleasant. Just as you notice the temperature when you put your hand on the wall at night after a very hot day. The wall remains warm for a while. But why? People are interested in understanding, but it is difficult to understand in a concrete way and with confidence in the information.”

According to the research, this is due to issues such as the deficiencies in school curricula when addressing this subject. In a study with 1.111 participants, the vast majority of whom had a high level of education (89% had a college degree or master's degree), it was found that there was an interest in the subject, but also the circulation of conceptual misconceptions, such as thinking that the hole in the ozone layer is responsible for climate change. Problems such as ideological warfare and misinformation surrounding the subject also interfere with efforts to educate the population about it.

“People feel that it is warmer, that there are more extreme events, but this still does not mean that all of them receive quality education about the climate. In general, they are unable to connect the factors, and that is our role. The connections that science brings us are very important for life in society,” Zezzo observed.