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The city of 77 climates

The temperature in the biggest Brazilian metropolis varies by up to 10 degrees at the same moment

It is ten o’clock in the morning on September 3 in Brazil’s largest metropolis. The year, 1999, when one of the measurements was made in the research that this story is based on, but the scenario has changed little in this time. In the middle of the corridor of buildings and the traffic noise the Paulista Avenue, it is common to see men in dark suits and women parading on high heels in trouser suits, almost always black. Because of the 28º Celsius, untypical for a sunny morning at the end of winter, the clothes seem rather unsuitable, but they are de rigueur for working in the country’s largest financial center – and, it is true, the temperature can fall in the evening. Eight kilometers to the west of there, at the same time, the storekeepers in the Lapa municipal market serve their customers in shirtsleeves – in the environs of the market, the temperature is 32º Celsius. 10 kilometers from there, in a district on the opposite side, in Moóca, the heat faced by the tradesmen and inhabitants is no less intense.

The difference in temperature, which bothers the people who live in São Paulo, may come to ten degrees at the same time of the day between two points close to each other, like the Tietê Ecological Park and the Tietê Ring Road, ten kilometers away from each other. The people who suffer most from this peculiarity of the largest Brazilian city are those who live in shantytowns or slums, time after time pushed to regions increasingly distant from the center. Their houses, unprepared for facing up to the swings in temperature, are like ovens during the day and refrigerators at night.

Putting on and taking off warm clothes – and, of course, the propagation of precarious housing, in which 12% of the 10 million inhabitants of the capital live – is a consequence of the disorderly growth of the metropolis, now scrutinized with this month’s publication of the Environmental Atlas of the Municipality of São Paulo, a project run by the municipal secretariats for the Green and the Environment and for Planning, with the support of Biota-FAPESP, a program for surveying the flora and fauna of São Paulo. The Atlas, the first results of which were announced in December 2000 (see Pesquisa FAPESP nº 60), is now to be found on the Internet (http://atlasambiental.prefeitura.sp.gov.br). The research project on which it was based “is the result of a paradigmatic partnership between the municipal public authority and the research system of the State of São Paulo”, comments José Fernando Perez, FAPESP’s scientific director, in the preface to the book. “The success of this enterprise ought to prompta reflection on the potential for this possible and necessary relationship, but still so little exploited.”

The Atlas shows how the 200 square kilometers that still remain of intact vegetation in the municipality, equivalent to 13% of its territory (1,512 square kilometers) are distributed. In the course of its almost 450 years, to be completed at the beginning of 2004, the construction of houses, buildings and factories has brought down 87% of the native vegetation in São Paulo’s capital city. According to this study, coordinated by geologist Harmi Takiya, the sub-mayor of Moóca, the city lost one fifth of its natural vegetation between 1990 and 2000. Today, its trees are concentrated in the 39 state and municipal parks and in a few districts – Jardins, Pinheiros and Morumbi, in the Western Region, and Moema, in the part of the Southern Region that is closest to the Center. But as one follows one’s course to Capão Redondo and Jardim Ângela, in the heart of the Southern Region, the city’s longest arm, some 20 kilometers from the Center, the trees become scarce. An absolutely urban horizontal landscape gainsspace, with sparse buildings and impressive clusters of precarious housing – and the temperature rises, slowly. In districts closer the Mar mountain range, like Marsilac, because of its closeness to the Capivari-Monos reserve, the temperature is far lower, oscillating around 23º Celsius.

Mosaic of microclimates
In one of the strands of the work of the Atlas, a team from the University of São Paulo (USP) discovered that, as a consequence of the distinct ways of occupying the urban space, the city shows 77 different climates – as seen in a broader conception, which besides the temperature and humidity of the air, takes into consideration the factors that alter the characteristics of the climate and influence people’s well-being, such as the predominant kind of construction (more or less houses, buildings or shantytowns) and the intensity of the traffic, since the temperature can go up with the heat emitted by the cars and pollution. The result is a mosaic that takes on homogeneity at the extremes of the city, because of the closeness to the Cantareira mountains, to the north, and to the Mar range, to the south. There is also a certain uniformity in the districts that encircle the Center, in a curve that starts in Barra Funda, in the Western Region, passes through Limão and Santana, in the North, advances to Penha and Vila Matilde, in the East, and ends in Sacomã, in the Southern Region of the city. There are temperature variations within the districts themselves, in streets or squares, for which reason these climates can also be called microclimates. But the mosaic gets jumbled up, with more marked differences in temperature, in the portions of the Western and Southern Regions close to the Center (see map).

One of the main causes for such a great variation is the clearing of the vegetation, associated with clandestine building lots and shantytowns that are disseminated at the extremes of the city. Added, to start with, to the damage from devastation, according to a study coordinated by geographer José Roberto Tarifa, is the impact caused by the impermeabilization of the ground: São Paulo has today 60,000 kilometers of paved roads, which retain heat and thus make the city hotter. There is also a strong influence from the daily circulation of 3 million cars in the city. Besides generating heat by burning fuels, which corresponds to one tenth of the energy that the city receives from the Sun, these vehicles launch into the air 2.6 million tons of pollutants a year, according to the State of São Paulo Basic Sanitation Company (Cetesb) – and, the more smoke in the air, the more heat. Add to this the concrete from 4 million houses and buildings. The result: the temperature tends to go up even more with the density of vertical constructions – an effect known as heat islands. The historical center of São Paulo is an exception. The density of skyscrapers is so high that the opposite effect arises, cold islands: in many buildings, the lower floors do not receive any sunlight.

When he began to study the climate in São Paulo 30 years ago, Tarifa did not accept the idea that environments so different – the tree-lined streets of the Jardins and the gray carpet of the houses in the Eastern Region – could have the homogeneous climate seen in the classical vision of physicists and meteorologists. “The studies would be segmented and assess just one or other aspect, like the rain or the pollution”, says Tarifa, who straight after retiring from USP, in 2002, was hired by the Federal University of Mato Grosso (UFMT), in Rondonópolis. “The old view did not take into consideration that the life of people in São Paulo undergoes the influence of, for example, the quality of the air and of thermal comfort.” He thinks that the change in the way of analyzing the problem was necessary too, because there are periods of the day in which the activities of the inhabitants, like commuting to work, weigh more than the topography to define the temperature in a specific region at a given time of day.

Tarifa and Gustavo Armani, another geographer, from USP’s Climatology and Biogeography Laboratory, put together the studies of the climate in São Paulo carried out from 1970 to 2000 and compared the data with aerial photographs of the city and images from Landsat 7. It was using this database that they listed 18 variables related to the climate of the city. The climate of a region is defined initially by eight of them, such as the ground surface temperature, the humidity of the air, and the quantity of rain. The other ten factors regulate these basic characteristics: these are the so-called climatic controls, like the emission of pollutants, the proportions of plant cover, and the density of the population and of buildings. The final result – the 77 climates shown in the book The Climates of the City of São Paulo – Theory and Practice, published in 2001 – makes it clear that these expressions of urban conditions are today more important in defining the metropolitan climate that the topography itself, one of the main determinant factors of the characteristics of natural climates until the beginning of last century.

São Paulo grew out from a hill between the Tietê and Tamanduateí Rivers, at an altitude of 720 meters, on top of which the Jesuit priests José de Anchieta and Manuel da Nóbrega created the College of Saint Paul of Piratininga in a precarious wooden cabin. From there, the inhabitants first took to the flatter and lower grounds. At a second moment, they advanced en route to the rise known by the geographers as the central ridge, at 800 meters above sea level, one which today districts like Sumaré, Cerqueira César, Vila Mariana and Jabaquara are settled. The highest stretch of this corridor is the Paulista Avenue, which up until 1900 was no more than a bucolic collection of small farms and mansions.

Since the beginning of last century, the city’s population, then with 240,000 inhabitants, has multiplied by 40, and today it spreads even over areas that were previously difficult to access, like the Cantareira range, a natural barrier of 1,200 meters in altitude. “Every time the space is altered, the climate is redefined”, Tarifa explains. Hemmed in to the north by the Cantareira mountains and to the south by the Mar range, Brazil’s largest metropolis is located in a corridor that facilitates the entry of masses of cold air coming from Antarctica and of the currents of air laden with humidity from the Atlantic Ocean, only 45 kilometers away in a straight line – even today natural elements responsible for the relatively mild temperature of the city.

Land without drizzle
From the days of the Jesuits up until now, São Paulo has devoured almost all the green around it and ceased to have a mere five climates, as it had five hundred years ago, at the time of the discovery. The five types were variations of the Tropical climate, marked by a dry and cold season, which extends through the autumn and winter, and another one, hot and rainy, during the spring and summer, with average temperatures that varied between 15º Celsius and 25º Celsius. According to a study carried out at USP’s Astronomy, Geophysics and Atmospheric Sciences Institute, the average temperature of the city has gone up 1.3º Celsius over the last 40 years. Up until the 60’s, the capital was still the Land of Drizzle, on account of the fine and assiduous rain that was added to a colder climate than the current one. In the winter, the citizens of São Paulo would not do without thick overcoats, gloves and scarves.

Such a great diversity of climates is not exclusive to São Paulo. To a greater or lesser extent, it also exists in metropolises around the world, like Mexico City, Santiago, in Chile, and Buenos Aires, in Argentina. “Such marked variations in climates arise when people abdicate the dream of a life in harmony with the environment”, comments Tarifa. “It’s a phenomenon that occurs when the logic of profit comes to determine the way how the spaces ought to be occupied.”

The Project
Environmental Atlas of the Municipality of São Paulo (nº 99/10955-9); Modality Regular Line of Grants for Research, integrated with the Biota/FAPESP program; Coordinator Harmi Takiya – Secretariat for the Green and Environment; Investment R$ 148,845.00

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