全球变化知识资源中心

The study of urban climate change has to take into account two components: global warming and microclimate variability due to urban growth.

The present article tries to quantify the global and local components in six Italian towns over the last fifty years: Milano, Bologna, Roma, Napoli, Bari and Palermo. Historical temperature series measured in the city centre and in the suburbs of the towns have been investigated: the Climatological Normals 1961-1990 and 1971-2000 have been compared with the mean data of the last 15 years (2001-2015). Everywhere the mean temperatures have been higher in the city centre than in the suburbs and both have progressively raised over time. Conversely, the differences between city centre temperatures and suburban ones have decreased. Mean temperature differences between the two kinds of monitoring sites can be considered as a first rough estimate of the urban contribution to local warming up. To better analyse the local effects of urban warming and their relation with health and welfare of urban residents, a quantitative spatial analysis of hot extreme events in Milano has been performed, as Milano is subject to stable atmospheric conditions in more than 60% of days per year. Such conditions contribute to the accumulation of waste heat generated by urban energy usage. Dry and moist heat waves have been treated, resulting in quite different spatial distribution of such events, as a strict effect of built and green areas in urban texture.