More heatwaves recorded annually in Spain and other countries

Spain has been hit by several record-breaking heatwaves this summer. In fact, Spain is among the regions where more heatwaves are recorded every year, and their effects indicate a rise in the risk of mortality of between 10 percent and 20 percent during these extremely hot periods. This is one of the conclusions gleaned from an international study in which the Spanish National Research Council (CSIC) participated. The study analysed heatwaves occurring between 1972 and 2012 in 400 cities and across 18 countries, and their effects on people's health, including mortality. The results are published in the journal Environmental Health Perspectives.

"Although from a health point of view a heatwave is described as a day on which the temperature exceeds a certain threshold, there is no internationally agreed definition," says scientist Aurelio Tobías from CSIC's Institute of Environmental Assessment and Water Studies. Led by the London School of Hygiene & Tropical Medicine, and working within the framework of the International Multi-City and Country Collaborative Research Network Programme, this work is the first to use a common methodology to evaluate the effects of these hot spells on mortality.

Among the study's conclusions is that the higher the temperature, the greater the risk to people's health. However, after analysing the data, the researchers determined that the risk is similar whether high temperatures occur over several days or on a single day. In addition, the study considers that the effects on health can last for up to three to four days following a period of excessive heat.

"We have also found that people living in relatively mild or cool areas are more sensitive to hot spells of weather than those in more extreme regions. This suggests that there is some acclimatisation to these extremes of heat," Tobías adds. Given that climate change projections indicate an increase in temperatures of around 2 °C, and therefore, an increase in the number of heatwaves, this study offers useful information on how better to adapt to periods of excessive heat as well as developing migration strategies.