Green urban areas, and to a certain extent also water areas, contribute to cool the city. It can be expected that a high share of green areas reduces the urban heat island effect and provides access to cooler open space. The actual effect depends however on more variables, like the size distribution and position of the areas, wind pattern etc.

Population density can also be used as an indication for the urban heat island effect. High population desities are associated with the lack of green space, high building mass, high production of anthropogenic heat per area.

Climate-change projections suggest that European summer heatwaves will become more frequent and severe during this century, consistent with the observed trend of the past decades. The most severe impacts arise from multi-day heatwaves, associated with warm night-time temperatures and high relative humidity. Heatwaves include tropical nights (minimum temperature exceeding 20°C) and hot days (maximum temperature exceeding 35°C).

The temperature map is the result of climatic modelling and represents the number of combined tropical nights (T > 20°C) and hot days (T > 35°C). Three different layers for the periods  1961-1990, 2021-2050, 2071 to 2100 are available.

Heat wave risk of European cities

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Alex E

Ecoclimax is defined by Odum (1969) as the culmination state after a succession in a stabilized ecosystem in which maximum biomass (or high information content) and symbiotic function among organisms is kept per unit of available energy flow.