A new study has found the recent heatwave in Spain, Portugal, Morocco and Algeria would have been almost impossible if it wasn't for climate change.

Working at breakneck speed, an international team of ten climate researchers from World Weather Attribution (WWA) published their study today, just eight days after the peak of the heatwave.

The research found that climate change made the heatwave at least 100 times more likely, with temperatures 3.5°C hotter than they would have been in a world without human-caused climate change.

The sweltering heat broke records in each of the four countries with temperatures reaching 36.9-41°C, which were up to 20°C higher than typical April temperatures.

“Silent killers”

Roop Singh, Senior Climate Risk Advisor at the Red Cross Red Crescent Climate Centre, and a contributing author of the study, says heatwaves occurring earlier than expected can be especially devastating.

“Early season heatwaves tend to be deadlier as people have not yet prepared their homes or acclimated to summer temperatures.

Heatwaves are often described as “silent killers” because it can take authorities weeks or months to fully understand just how many deaths are linked to an individual event. Singh also notes that heatwaves are among the deadliest disasters in the world.

According to the World Health Organisation, heatwaves in 2022 contributed to nearly 4000 deaths in Spain and over 1000 deaths in Portugal.

A separate study has found that every year, heatwaves lead to an average of 262 deaths in Algeria and 250 deaths in Morocco.  

Heatwaves are most dangerous for the elderly and poorer people, who have reduced access to air conditioning, greenspaces, shade, and water.

Singh says deaths from heatwaves are preventable. She points to Spain’s introduction of heatwave adaption measures that include early warning and heat advice as “exactly the type of adaptive heat action we need to see more of.”

Heatwaves are becoming hotter, longer, and more frequent due to climate change.

According to the WWA study, if global temperatures rise a further 0.8°C to a total warming of 2°C, a heatwave like the one that impacted Spain, Portugal, Morocco, and Algeria would be 1°C hotter.

Dr Friederike Otto, Senior Lecturer at the Grantham Institute and a founder of World Weather Attribution, says the study highlights the need for urgent action to avoid more intense heatwaves in the future.

“The Mediterranean region is already experiencing a very intense and long-lasting drought and these high temperatures, at a time of the year when it should be raining, is worsening the situation.

“Without rapidly stopping the burning of fossil fuels and adaptation towards a hotter, drier climate, losses and damages in the region will continue to rise dramatically.”

Science at speed

WWA studies are performed at a faster pace than most scientific studies

Once the team decides to study an extreme weather event, the results are published just days or weeks later to inform discussions about climate change, mitigation, and adaptation.

Today’s study  is one of WWA’s fastest , completed in just eight days.  

“We have a small team of people who know exactly what they are doing and have done it many times in different contexts, so that is what allows us to do it so fast,” explains Dr Otto.

Organised over Zoom calls and in flurries of emails, the speedy science is carried out by an international team of climate scientists and risk experts.

Dr Sjoukje Philip, Researcher at the Royal Netherlands Meteorological Institute and one of the authors of the study, says the timeline balances public interest and the amount of work required for the weather event being studied.

“This time we decided to do a very rapid analysis simply because people were waiting for the results and qualitatively [the results] wouldn’t be different if we used more time.

Pointing to previous WWA studies on heatwaves, Dr Philip explains that even if the researchers carried out further modelling on the event, it is unlikely the work would have changed the main findings.

The return of El Niño

As sea temperatures increase in the Pacific Ocean, heatwaves, like the one seen in Spain, Portugal, Morocco and Algeria, could become even hotter later this year.

The El Niño–Southern Oscillation (ENSO) is a natural phenomenon involving the warming and cooling of the Pacific Ocean, driven by equatorial trade winds.

The climate pattern was first observed by fisherman in Peru in the 1970s, who coined the Spanish names La Niña – the girl and El Niño – the boy.

‘El Niño’ refers to the warming of the Pacific Ocean which leads to warmer global temperatures, while ‘La Niña’ refers to the cooling of the Pacific Ocean which leads to cooler global temperatures.

During the last strong El Niño in 2016, the world recorded its hottest year on record. Since, ENSO has been in a neutral or La Niña phase, which has limited global temperature rises.

However, in recent months the Pacific Ocean has warmed rapidly and this week, the World Meteorological Organisation estimated that the there is a 60% chance that El Niño will return by the end of July and a 80% chance that it will return by the end of September.

Dr Otto says El Niño will likely exacerbate the impacts of climate change.

“If El Niño does develop, there is a good chance 2023 will be even hotter than 2016 – considering the world has continued to warm as humans continue to burn fossil fuels.

“El Niño will only worsen the impacts of climate change that we are already experiencing – hotter heatwaves, more severe drought and more extreme wildfire.”