Scorching Cities Like Buenos Aires Are Not Just About Global Warming
Buildings, tarmac and air conditioning are turning some cities into fetid, airless saunas. Experts urge more trees and grass to mitigate the heat of increasingly hot cement jungles.
BUENOS AIRES — Buildings, tarmac and the colonial laws of Spain will make us suffocate from heat. For we are not suffering from high temperatures just because of global warming. On an ordinary summer day in Buenos Aires, the thermal sensation is almost five degrees Celsius higher than Greater Buenos Aires and 10 more than in country areas. Why? Because of buildings, tarmac and the Laws of the Indies.
Let's take it in parts. All big cities suffer from the so-called heat island effect, which has four causes. The first is lack of trees, bushes and plants that create shade for buildings and cool the air through evaporation. Second is the proliferation of impermeable material on buildings and of dark pavement like asphalt that absorbs heat. Third is the lack of ventilation between buildings. And the final cause is the heat given off by cars and air conditioning.
Evidently, Buenos Aires has all these conditions, even though it does have many trees and parks. They could be better distributed, and there should perhaps be more.
To make the situation even worse, our city is a daughter of the laws and norms Spain imposed to rule the Americas, which were mistaken in certain areas.
Now, the Spaniards meant no harm (don't get me started on that), but they lacked imagination. In the early 16th century when those laws were compiled, nobody thought cities could become what they have today. For example, Spanish colonial law envisioned preventing, not encouraging, local winds. The laws stated that the streets should be traced outward from a central square with corners in the same direction as the main winds. Thus Buenos Aires was built with the Plaza de Mayo facing east to west and its junction with the Yrigoyen and Bolívar streets facing southwest, whence comes the vigorous Pampero wind.
The corner of Yrigoyen and Balcarce faces southeast, where the southeastern wind comes in. Our peninsular ancestors didn't want the wind to blow along the avenues and raise dust and goodness knows what else.
Buildings block breezes
We were deprived of these main winds then, though colonial streets did allow the movement of breezes from the Río del Plata. That is, until the city grew with more and more cement and asphalt, which helped accumulate heat. A recent study from the Journal of Geophysical Research concluded that accumulation of heat in cities hinders air circulation and increases pollution. So long then, breeze from the Río del Plata!
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Opening the windows in the Argentine capital. Photo: Herman Pinera
Certainly there is global warming and we all suffer it, but in cities like Buenos Aires, insufficient greenery, buildings and tarmac make it much hotter than surrounding regions. Our founder Pedro de Mendoza wasn't wrong to plan the city facing a river, but because everything we build now blocks its pleasant breeze, we can see how Buenos Aires has become overheated and its air polluted.
Two recent studies confirm this. Specialists considered how the wind behaves in very polluted cities. Houston, one of the most polluted in the United States, is in this sense very similar to Buenos Aires. It is close to a bay, a few kilometers from the Gulf of Mexico, but building development has blocked the winds that used to take smog out to sea by night. Yet buildings are not the only, or even the primary, cause of this effect in Houston. It's the heat from sidewalks that changed the conduct of winds and ensured that polluted air would hover over the city.
The author of that study, Fei Chen, believes that unfettered city growth could curb winds even more and increase pollution. "Air circulation should today be a fundamental concern in designing cities," he says.
Paradoxically, for refreshing breezes to blow, a city's temperature must be reduced and for that, experts urge cities to plant more trees and grass and build a recreational lake or two.