Last summer, in 2023, 10,958 deaths were associated with high temperatures. So far in the summer of 2024, 56 deaths have already been attributed to extreme heat, 7 of which occurred on days of excessive heat. These figures were recorded by the Heat-Attributable Mortality in Spain (MACE) application.
Climate change and rising temperatures are increasing the mortality burden related to heat, especially in tropical and subtropical regions where extreme and prolonged heat will become more frequent. This trend has been a growing concern for the scientific community since at least the anomalous summer of 2003. The accumulation of evidence on this phenomenon led a team of scientists from the Institute of Environmental Assessment and Water Research (IDAEA-CSIC), the University of Valencia, and the Climate Research Foundation (FIC) to develop the MACE application.
This tool uses official data from Spain’s Daily Mortality Monitoring System (MoMo) and temperature records from the Spanish Meteorological Agency (AEMET) to calculate heat-attributable mortality—categorized as moderate, extreme, or excessive—for the months of June, July, and August.
“If we talk about the health impact of heat, the summer of 2023 was the third-highest in heat-attributable mortality, with 3,934 deaths, following the heatwave of 2003 and the summer of 2022,” explains Dr. Aurelio Tobías, an environmental epidemiologist at IDAEA and co-author of the application.
The summer of 2023 experienced four heatwaves, starting on July 9, with a total of 24 days (not consecutive) under heatwave conditions. This summer, 2024, while initially offering a brief respite from high temperatures, announced its first heatwave on July 18. Temperatures exceeded 35°C across much of the southern half and northeastern quadrant of the Iberian Peninsula. After a two-day reprieve, AEMET announced a second heatwave starting Tuesday, July 23, with maximum temperatures expected to surpass 40°C and persist until July 28.
In such circumstances, the protocols outlined in Spain’s National Plan for Preventive Actions Against High Temperatures, issued by the Ministry of Health, are activated. This plan includes temperature forecasting, mortality information, coordination with health and social services to identify at-risk groups, and collaboration with relevant administrations and entities.
Updates to the MACE application
Since its implementation a year ago, the MACE application has incorporated several updates to enhance its utility and precision. One of the most significant improvements is the inclusion of detailed data for each province in Spain, providing a more accurate understanding of heat’s impact across different regions. Recognizing that the threshold for extreme heat varies across the country is crucial. For example, a temperature of 26°C may be considered extreme in northern Spain, whereas in the south, where temperatures are generally higher, extreme heat thresholds can be much higher. MACE accounts for these region-specific thresholds to offer more accurate estimates of heat-attributable mortality.
How can MACE help reduce heat-related deaths?
This tool represents a knowledge transfer from research to society, addressing the potential health impacts of heat.
“If citizens are aware of the risks of extreme heat to their health, the application can help drive behavioral changes to cope with high temperatures. Measures include staying hydrated, staying in cool places, reducing outdoor physical activity during peak heat hours, wearing lightweight breathable clothing, and eating light meals to replenish lost minerals,” adds Dr. Tobías.
For public administrations, the newly available provincial data allows for more precise identification of areas most vulnerable to heatwaves, enabling targeted efforts. Alert and prevention protocols can become more specific and effective, reducing mortality rates.
Dr. Dominic Royé, co-author of the application and head of data science at FIC, highlights that Spain is particularly vulnerable to climate change due to its geographic location, aging population, and socioeconomic conditions. For this reason, the authors urge health authorities in Spain to develop action plans that reduce exposure to extreme temperatures, enhance epidemiological surveillance and healthcare services, and promote public awareness and education on climate-related health risks.
