The episode of extreme heatthat we suffered last week, in the middle of spring, and that raised the thermometer in Cordoba to 38.8 ºC, a historical record in the Peninsula for the month of April, "would have been almost impossible" without man-made climate change. That's the conclusion of a rapid attribution analysis by an international team of leading climate scientists from the World Weather Attribution (WWA) group.

The study, published this Friday, not only focuses on Spain, since that heat episode that frames between April 26 and 28 also affected Portugal, much of Morocco and northwestern Algeria.

This is one of the so-called attribution studies carried out by WWA climate scientists to determine if an extreme weather phenomenon can be linked to climate change, because although one of the main consequences of global warming is the increase in the occurrence and intensity of droughts, heat waves or floods caused by major storms, A direct relationship cannot always be established.

According to the ten researchers who signed this study, there was last week during the episode that, depending on the region, caused temperatures to be recorded up to 20 degrees higher than usual in a month of April: climate change made the episode of extreme heat at least 100 times more likely.

Without in Spain thehighest temperature was the 38.8 ºC recorded in Córdoba on April 27, Portugal reached 36.9ºC in Mora (the Portuguese record so far was 36 ºC measured in Pinhão, in 1945) and remained close to Amareleja (36.7 ºC), Neves Corvo (36.5), Alcácer do Sal (36.3), Alvalade/Sado (36.2) and Portel (36.1). With 32.4 ºC, Lisbon also broke its record for April, according to data from the Portuguese Institute of the Sea and Atmosphere (IPMA).

In Moroccan cities such as Sidi Slimane, Marrakech and Tarudant, temperatures exceeded 41 ºC, while in Algeria, Maghnia or Mascara-Ghriss they were more than 40 ºC on April 28.

They are temperature records that have been broken "by a long margin, as has happened in other recent heat waves in the world," says Sjoukje Philip, co-author of the study and researcher at the Royal Institute of Meteorology in the Netherlands.

"While Europe and North Africa have experienced heat waves with increasing frequency in recent years, the recent heat in the Western Mediterranean has been so extreme that it is also a rare event even in this warmer climate that currently exists," the authors write. According to their estimate, the average temperatures observed during those three days have a return period of approximately 400 years (at least 60 years) in the current climate, which means that there is about a 0.25% chance that they will occur in a given year.

These heat records also occur in the context of a multi-year drought, further increasing the impacts on agriculture , already badly affected by "the lack of water derivedfrom a combination of the effects of climate change and water use," according to the study. "Early heat waves and associated drought conditions threaten the yield of many crops such as wheat. This heatwave has come at a critical time for the agricultural season in the Western Mediterranean countries," write the scientists, who note that extreme heat in the Mediterranean is increasing faster even than models estimated.

As Friederike Otto, co-author of the study and researcher at the Grantham Institute for Climate Change and the Environment, points out, "The Mediterranean is one of the regions in Europe most vulnerable to climate change. It is experiencing a very long-lasting and very intense drought and these very high temperatures at a time when it should be raining aggravate the situation."

In a scenario of an average temperature increase of 2 ºC compared to the one at the beginning of the industrial era (0.8 ºC more than the current temperature, therefore), a heat wave like the one we have suffered would have been one degree warmer, an estimate that even the scientists who make it consider "very conservative".

Heat wave vs heat episode

Although the authors of the attribution study speak of a heat wave, technically in Spain it has not been considered a heat wave, as Rubén del Campo, spokesman for the State Meteorological Agency (Aemet), points out: "The first thing to keep in mind is that there is no universal or unique definition of a heat wave. And this can be approached from different perspectives, such as the temperature threshold from which there may be an impact on people's health, but we rely on the climatic anomaly."

To differentiate it from a heat episode, in Spain it is considered that a heat wave occurs when, for at least three consecutive days, at least 10% of the country (of the stations considered) register maximums above the 95% percentile of its series of maximum temperatures of the months of July and August during the reference period. "Obviously in this episode the temperatures have been much higher than usual in April, but not than in July and August," says the meteorologist.

Thus, according to the definition used by Aemet, theearliest heat wave that Spain has suffered was on June 11, 1980, although in 2022 we also had an early wave, as it began on June 12.

A man refreshes himself in a fountain in Écija (Seville)CARLOS GARCÍA POZO

Although last week did not exceed 40 ºC in any Aemet station, as it was pointed out that it could happen, it was an extraordinary episode that broke records in more than 40 of the 90 main stations of the Aemet network, as Ricardo Torrijo advances. This spokesman for the State Meteorological Agency stresses that what they still handle are provisional data, waiting for the final reports to be made in April. "In addition to those 90 main stations, we have many, many more that will require more careful analysis," he says.

The temperature record of the April episode was those 38.8 ºC recorded last Thursday at the airport of Córdoba, which superseded the 38.6 ºC measured on April 9, 2011 in Elche (Altabix), until now record in an April in the Peninsula. Last week, other stations near the airport of Córdoba marked temperatures of 38.5 ºC and 37.9 ºC. The national record is still held by La Aldea de San Nicolás, in Gran Canaria, which marked 40.2 degrees on April 20, 2013.

Heat deaths

The scientists who signed this attribution study stress that "heat waves are among the natural phenomena that cause more deaths each year, although the real impact is often not known until weeks or months after it has occurred, once all the data is collected or scientists can analyze the excess deaths. In any case, they warn, in many places heat deaths are not well counted so they consider that the estimates that exist are probably below the real figures.

"Although verified mortality data from the current heatwave are not yet available, we do know that in 2022 heat waves contributed to almost 4,000 deaths in Spain and more than 1,000 deaths in Portugal (WHO, 2022)," say the scientists, who recall that "every year, an average of 262, 250 and 116 people die from heat-related illnesses in Algeria, Morocco and Tunisia, respectively (Hajat et al., 2023)". In Tunisia, a review of all-cause mortality between 2005 and 2007 found that for every degree Celsius above 31.5°C, daily mortality increased by 2%.

Although the inhabitants of Mediterranean countries are used to dealing with high temperatures, scientists stress that early heat waves like those of last week tend to be particularly deadly due to the lack of acclimatization of the population and that they catch us off guard (for example, many people have not yet taken out their fans or air conditioners). and the effects on agricultural crops.

However, this scientific team also highlights good news linked to adaptation: "Heat-related deaths have decreased in cities with urban planning for extreme heat. This has been effective in Spain, and especially in Lisbon (Portugal), where the urban heat island effect has been reduced by incorporating more green and blue spaces. In addition, early warning systems for heat, simple self-protective gestures such as drinking enough water, urban heat plans, strong social ties and improved risk perception have been shown to reduce health impacts.

"In Spain we have seen that the implementation of heat adaptation measures has been advanced, which is exactly the type of actions we want to see more to reduce deaths from this cause," says Roop Singh, advisor to the Red Cross Red Crescent Climate Center.

  • Environment
  • Heat wave
  • Climate change

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