The urban heat island effect

Summer is here and with him the desire of millions of people to escape the city. The east desire is more than the mere enjoyment of the beach, leisure or rural landscapes, there is also the prevailing need for escape heat. And part of the fault of this lies in the so -called urban heat island effect.

What is the urban heat island effect

Heat island? The term refers to the fact that cities They tend to accumulate heatwhich implies that the temperature in them is usually higher than in their surroundings. This effect can be felt during the day but it is perhaps at night when the difference between urban temperature and that of its surroundings is greater.

The difference can be several degrees. An estimate For example, he calculates that the difference between New York City its surroundings is around the 4th Celsius. A recent study made in five Spanish cities estimated that the average variation in Madrid was 1.3º, but in Valencia reached 4.1. The responsible team came to measure differences of up to 11 between the center and the periphery of the Spanish cities studied.

How a heat island occurs

The causes of the heat islands There are several and diverse. The construction materials we use tend to absorb energy that they release during the night. This makes night temperatures do not descend in the city as much as in other contexts, thus accumulating heat.

The buildings, in addition, block the passage of the air that would drag the heat accumulated in the day to day, while the absence of trees and of phenomena such as the evaporation of soil water contribute to a worst thermoregulation of the system.

The other great factor responsible for urban warming is human activity. Many of our activities, from driving to heating a pout generate residual heat. Even when we cool things, for example when we use the air conditioning, the thermal “balance” is positive.

What factors aggravate the problem

We pointed out before not all cities experience a heat island of the same magnitude. The complexity of the factors that cause this phenomenon is responsible for it. Knowing this, we can list some factors that can influence the degree in which a city stands out from its thermal environment.

Among these factors We could find Population density, orientation and structure of its street, characteristics (height, materials) of its urban buildings, vegetation and trees, the passage of rivers, or its location with respect to geographical elements such as the mountains or the coast. Even the color of the buildings, including its roofs, affects the temperature differential.

Consequences of the heat islands

The direct consequence of this phenomenon is an increase in temperatures, which in turn affects a multitude of Aspects of everyday life of whom these cities inhabit. Both at night and day.

Heat can have consequences on our health and well -being: heat strokes, Difficulty reconciling sleep or to concentrate or an increase in the risk of suffering the effects of certain diseases such as cardiovascular, among other problems.

Urban heat can be somewhat positive in winter or certain climates from the energy point of view, but in summer it will imply that we will spend more to cool our homes, work areas and even our refrigerators.

A problem that will go to more

There are two factors that invite you to think that this phenomenon and its consequences will go worse in the coming years. The first, climate change. Perhaps the phenomenon that we mostly associated with climate change is the increase in the average temperature of the planet. This temperature increase can be added to the increase associated with urban heat island, thus increasing the risks and problems associated with this phenomenon.

The second factor to consider are migrations, specifically the rural exodus. A growing proportion of people live in cities, some of them already host dozens of millions of people. The biggest cities They are more susceptible to suffering the problem of urban heat island. In addition, the more people live in them, the more people the impacts of this temperature increase will be vulnerable.

How to prevent the heat island effect

Urbanization is a process that continues, especially in the “developing” countries, so all we can do is search ways to reduce impact of these heat islands. To do this, understanding its causes and dynamics is essential.

The solutions that They have been proposed To avoid heat accumulation in cities are diverse, but the possibility that they can be implemented depends on various factors. For example, in an area still under development, we can encourage architectures that optimize air flow and reduce the presence of materials that capture heat easily. It is also important to leave spaces to non -urbanized areas, natural and seminatural environments such as parks and urban forests.

The introduction of trees and other green areas () can also be feasible in already built areas. The mere Presence of trees On an avenue you can significantly reduce the insolation that reaches the ground and thereby prevent it from hot as much as it would happen without the trees. In this sense, even the use of paintings that increase the solar energy reflected again to the atmosphere (if we paint a roof or a white square, for example) it can also become a useful resource.

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Image | Fabian Lozano