Core Indicator 4: Bio-Climate/ Thermal Load(Katzschner, L., Burghardt, R. 2015)
The heat balance of the human organism is closely related to the atmospheric environment. Along with air temperature, wind speed, water vapour pressure and the medium radiation temperature are also relevant. Besides toddlers, whose thermoregulation is still unstable, people with health impairments, such as cardiac and/or circulatory insufficiencies or respiratory disorders, as well as elderly people particularly frequently suffer from health impacts of heat periods. Elderly people sometimes manifest multi-morbid disease patterns, which further reduce their capacity to adapt to heat waves. High-intensity rainfalls, floods and storms have a potential to cause acute injuries and psychological impairments (traumatisation).
In addition, a rise in temperature and extreme weather events also impact indirectly on human health – through a higher risk of microbial (re)contamination of drinking water, the increase of allergenic pollen and infectious diseases.
The climatic situation in Berlin is characterised by the influence of a continental climate with a higher potential for a heavy heat load in the summer months, which is additionally reinforced through the urban heat-island effect. Besides, at times of high-pressure atmospheric conditions in summer, the wind speed values, which on annual average are relatively high, undergo a significant decline of ventilation, so that this effect also reinforces the heating and lack of cooling of the city.
When the urban development plan for climate (Stadtentwicklungsplan Klima) ((StEP Klima, SenStadtUm 2011) was developed, the assessment of the bioclimatic situation was based on the dimensionless evaluation index "PMV". Methodologically, the assessment of the daytime and nighttime situations was carried out differently.
In order to determine the bioclimatic load in terms of the Berlin environmental justice approach, a different evaluation index, the PET, was additionally consulted. The reason lies primarily in the orientation of this evaluation approach, as the environmental medical component enters more strongly into its calculations. (cf. Table 2). The values of nighttime cooling were the determining basis for the evaluation.
However, the potential of heat stress during daytime was also taken into consideration, by counting the frequency of summer days with heat load. These were defined as days with a PMV value of at least 1.8, with simultaneous lack of nighttime cooling. Land use information such as the block-related development density formed the basis for the investigation.
The aggregated PET values were determined from these input data and served as a basis for assigning the planning areas to the three levels of bioclimatic load.
Tab. 2: PMV and PET index in comparison (VDI 1998; Matzarakis, A., Mayer, H. 1996; Katzschner et. al. 2007)
In order to be able to assess the factor bioclimate according to the Berlin environmental justice approach, the identified PET values had to be aggregated into a three-level scale.
Tab. 3: Three-level evaluation classification of the thermal index PET (Katzschner, L., Burghardt, R. 2015)
The analysis shows that all urban structures with dense development exhibit heat loads which are not sufficiently compensated, not even at nighttime. Half of the planning areas are affected by a high bioclimatic load. 170 planning areas suffer from a medium load and only 49 are load-free. Berlin-wide, altogether 65 planning areas exhibit a high bioclimatic load and a high density of social problems at the same time. In all, 612,000 inhabitants are affected by this. Planning areas which simultaneously have a bad social structure or high problem density as well as a high bioclimatic load are mainly situated in the following districts:
Thus, the dense extended inner city, mainly characterised by block structures, and the large estates in both of the former halves of the city are focal points.