The Urban Heat Island (UHI) is likely the most well-known concept from our field and the one that created most public awareness beyond our community. The simplicity and intuitive character of the island analogy were thereby essential for its success but likewise encompasses considerable conceptual limitations and misinterpretations. For instance, an island implies a defined background – the sea level –, while the rural background temperature can be quite variable around a city. Likewise, the island suggests a static character of its topography, but the UHI has a strong diurnal, inter-diurnal, and seasonal variation. Moreover, the varying spatial and temporal characteristics of the different UHI types create confusion and complicate the application of the concept. Finally, the UHI is a relative parameter, which is characteristic of the partial urban effect but only remotely informative regarding the absolute heat exposure.

Therefore, it has been argued before, that we should focus on urban overheating, intra-urban heat variation, more human-centric approaches, and biometeorological variables. On the other hand, to gain impact in policy, metrics need to be simple, understandable and fit-for purpose (i.e. for assessing urban overheating risks and the effectiveness of mitigation measures), and the respective data needs to be available. If we do not manage to deliver these metrics, other players will fill the gap, who might be less concerned about scientific rigor.

In this session, we want to discuss these conflicting priorities and ways ahead. We seek contributions beyond UHI indicators, which fulfil the above criteria and ideally build on the success of the UHI to deliver policy-relevant information.