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Introduction
The term “heat island” describes a micro-climatic phenomenon that occurs in urban
environments. It consists of a relevant increase of air temperature within urban areas
which are thus generally warmer than the surrounding rural neighbourhoods.
Usually, the temperature difference is more relevant during the night than during the
day and it is most apparent when winds are weak.
At seasonal level, urban heat island phenomenon occurs in winter as well as in
summer, when it is more severe for the population living in the urban environment.
The UHI threat to human health within cities have to be carefully tackled: in fact,
the high summer temperatures heavily affect the quality of life in the cities producing a lot of negative impacts that may be summarized as a relevant deterioration of
human health with bioclimatic discomfort, as well as an increase in energy consumption (for example, because of the need of air conditioning) which in turn determines higher emission of air pollutants and greenhouse gases. These aspects make
urban agglomerations increasingly vulnerable to climate change. Although UHI
phenomenon is not a direct consequence of climate change, it is expected to exacerbate due to the predicted overall warming in the framework of climate change scenario for the second half of the century, when mean temperature are generally likely
to increase.
UHI phenomenon has been shown to be directly linked with the size of urban
areas and with population living inside. In this respect, it is likely to become more
severe in the forthcomings years due to the constant growing of the number of
people living in urban areas. In fact, global population is increasingly concentrating
in cities: since 2007 more than a half of the human beings is living inside urban
areas. In Europe, about 75 % of people is currently living in urban areas, with a
projected increase up to 80 % in 2020. As for the whole globe, in 2050 the share of
the urban population will reach almost 70 % of the total, implying that about 6.3 billion people will live in urban areas.
There are a number of reasons why UHI phenomenon affects urban areas. The
main cause is related to the physical characteristics of materials composing urban
surfaces absorbing rather than reflecting solar radiation (concrete and asphalt among
the others) so that the surplus heating of the surfaces determines the emission of a
large amount of long-wave radiation, especially during the night. In addition, urban
areas generally contains small portions of natural surfaces (vegetation in parks, gardens, etc.) which could contribute to maintain a stable energy balance. A further
factor related to the increase of temperature is the waste heat generated by energy
consumption (heating and cooling plants, industrial activities, transports, etc.).
Our cities and urban areas in general are facing many challenges – economic,
social, health and environmental. However, the proximity of people, business and
services associated with cities also creates opportunities to improve resource efficiency. Indeed, well-designed and well-managed urban settings offer great opportunities for sustainable living; partnership and coordination from the local to the
European level can support their improvement. Climate change has the potential to
Introduction
Introduction
The term “heat island” describes a micro-climatic phenomenon that occurs in urban
environments. It consists of a relevant increase of air temperature within urban areas
which are thus generally warmer than the surrounding rural neighbourhoods.
Usually, the temperature difference is more relevant during the night than during the
day and it is most apparent when winds are weak.
At seasonal level, urban heat island phenomenon occurs in winter as well as in
summer, when it is more severe for the population living in the urban environment.
The UHI threat to human health within cities have to be carefully tackled: in fact,
the high summer temperatures heavily affect the quality of life in the cities producing a lot of negative impacts that may be summarized as a relevant deterioration of
human health with bioclimatic discomfort, as well as an increase in energy consumption (for example, because of the need of air conditioning) which in turn determines higher emission of air pollutants and greenhouse gases. These aspects make
urban agglomerations increasingly vulnerable to climate change. Although UHI
phenomenon is not a direct consequence of climate change, it is expected to exacerbate due to the predicted overall warming in the framework of climate change scenario for the second half of the century, when mean temperature are generally likely
to increase.
UHI phenomenon has been shown to be directly linked with the size of urban
areas and with population living inside. In this respect, it is likely to become more
severe in the forthcomings years due to the constant growing of the number of
people living in urban areas. In fact, global population is increasingly concentrating
in cities: since 2007 more than a half of the human beings is living inside urban
areas. In Europe, about 75 % of people is currently living in urban areas, with a
projected increase up to 80 % in 2020. As for the whole globe, in 2050 the share of
the urban population will reach almost 70 % of the total, implying that about 6.3 billion people will live in urban areas.
There are a number of reasons why UHI phenomenon affects urban areas. The
main cause is related to the physical characteristics of materials composing urban
surfaces absorbing rather than reflecting solar radiation (concrete and asphalt among
the others) so that the surplus heating of the surfaces determines the emission of a
large amount of long-wave radiation, especially during the night. In addition, urban
areas generally contains small portions of natural surfaces (vegetation in parks, gardens, etc.) which could contribute to maintain a stable energy balance. A further
factor related to the increase of temperature is the waste heat generated by energy
consumption (heating and cooling plants, industrial activities, transports, etc.).
Our cities and urban areas in general are facing many challenges – economic,
social, health and environmental. However, the proximity of people, business and
services associated with cities also creates opportunities to improve resource efficiency. Indeed, well-designed and well-managed urban settings offer great opportunities for sustainable living; partnership and coordination from the local to the
European level can support their improvement. Climate change has the potential to
Introduction