Building-level maps locate heat-wave hot spots inside Bilbao, Madrid and Cáceres

"The risk posed by heat waves is not measured solely by temperature; it has multiple dimensions," said Irantzu Álvarez, a researcher in the SAREN group at the University of the Basque Country (EHU) ^[4]. The group is led by Leire Garmendia and studies ways to limit heat-wave damage to buildings and outdoor spaces ^[1]. The assessment follows IPCC guidelines ^[14]. For each place it asks how the buildings and public spaces are built, how hard high temperatures hit that part of the city, and how many people live there and how unprotected they are ^[5].

One of the group's own examples shows why social and physical data have to be combined. The researchers said that "a building may be sensitive to heat, but its residents may have the financial means to protect their home from it" ^[7]. A map built only from construction type or surface temperature would give that building the same rank as a neighbour whose residents cannot pay to cool it.

The work is part of the OLADAPT project, run with the Polytechnic University of Madrid, the University of Extremadura and the EHU's UNESCO Chair in Sustainable Development and Environmental Education ^[2]. Its three cities sit in different climate zones ^[3]. Running one procedure in all three is a test of whether it transfers, and the group says the method "is fully replicable; it can be used anywhere" ^[15]. Three Spanish cities show the procedure runs in three climates.

The group also says that "adaptation measures can be implemented much more effectively with this type of study" ^[13]. The published account does not report the numbers that would test this: how many buildings were scored, how the inputs were weighted into one score, how wide the spread is inside a neighbourhood, or whether high-scoring buildings saw more heat illness or deaths. Income and age were among the inputs ^[6]. So the finding that low-income and older residents are "far more vulnerable" ^[8] partly reflects how the index was built. It is not independent evidence that those residents suffer more in a heat wave.

I think the case for spending building by building holds in principle. "There may also be different situations within the same neighborhood, which is why this type of detailed research is necessary," the group said ^[9]. A single city-wide plan would allocate money by an average that hides those situations. The condition is that the scores track who actually falls ill when the heat arrives, and that check needs to come before the maps decide a budget.