In recent years, a series of studies have been carried out with the aim of analyzing the impact that high temperatures will have on mortality at different time horizons and under different climate scenarios.
Very few of these studies consider the fact that the threshold temperature used to define a heat wave will vary over time, and virtually none calculate this threshold temperature for each geographical area under the assumption that there will be variations at the country level.
The purpose of this study was to analyze the impact that high temperatures will have on mortality throughout the 2021-2050 and 2051-2100 periods under a scenario with high levels of emission (RCP8.5) and in a case: a) where adaptation processes are not taken into account; and b) where complete adaptation processes are taken into account.
We estimated that the mean daily maximum temperatures will increase by 1.6 °C throughout the 2021-2050 period and by 3.3 °C throughout the 2051-2100 period compared with those of the reference period (2000-2009). If no heat adaptation process takes place, the global annual mortality attributable to high temperatures in Spain will amount to 1414 deaths/year (95% confidence interval [CI]: 1089-1771) throughout the 2021-2050 period, and to 12,896 deaths/year (95% CI: 9852‑15,976) throughout the 2051-2100 period. If a heat adaptation process does take place, we estimated that the annual mortality would be 651 deaths/year (95% CI: 500‑807) throughout the 2021-2050 period and 931 deaths/year (95% CI: 770 1081) throughout the 2051-2100 period. Our results showed a high degree of heterogeneity, and the savings achieved between a situation that does contemplate an adaptive process and another one that does not was estimated at 49,100 million euros/year throughout the 2051-2100 period.
In conclusion, we observed a non-linear increase in maximum daily temperatures that varied greatly from one region to another, with an overall increase in the mean values for Spain as a whole that was not linear over time. The high degree of heterogeneity found in heat-related mortality among the different regions and the great differences observed when considering an adaptive versus a non-adaptive process indicates that adaptation plans must be implemented at a regional level.