Climate change helped enable this deadly heat wave — now, it has hit the Olympics

The heat wave baking Olympic athletes and fans in France already killed at least 21 people as it passed through eastern Europe and northern Africa in July, and a new scientific analysis published online today finds this intensity would have been "virtually impossible" without climate change.

That means without climate change, caused largely by humans burning fossil fuels and cutting down forests, temperatures would have been 3.3 C cooler.

Researchers from World Weather Attribution said heat waves like this would have been rare without human-caused climate change, but comparable events in the region can now be expected once every 10 years.

The "super rapid analysis" — which comes out while the extreme weather event is still happening instead of weeks or months later — was conducted by five researchers from universities and meteorological agencies in Sweden, the Netherlands, the U.K and the U.S., led by Mariam Zachariah at Imperial College London.

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Mike Tipton, a professor of physiology at the University of Portsmouth in England who has studied how heat impacts athletes, says both athletes and sporting event organizers are becoming more aware of the harms from extreme heat — and will have to spend more time considering how to mitigate the risk.

"Europe is heating twice as fast as other continents and even quicker than climate models predict," she said in a news release. "Analyses like these help people understand that climate change is not a distant threat, but an immediate one that is already making life on earth much more dangerous."

The analysis looked at average July temperatures in the region including Morocco, Portugal, Spain, France, Italy and Greece. 

Hot air masses from North Africa's Sahara desert caused a heat dome to develop over the Mediterranean by the first week of July, it said. That pushed temperatures up to 48 C in Morocco, killing at least 21 people. The researchers suggested there could be dozens or hundreds more deaths in the affected countries that have not been reported yet, as "the full impact of a heat wave is rarely known until months afterwards."

The heat helped wildfires spread through Portugal and Greece, worsened water shortages in Italy and Spain and forced Paris Olympics athletes to take measures such as draping bags of ice over their heads and shoulders when the heat wave hit France this week.

How scientists make the links

Many studies on the impacts of global heating gather data by taking measurements of extreme weather events and compare climate models that show the event's likelihood both with and without climate change. While today's study didn't use models, the scientists noted that it got results very similar to a World Weather Attribution study of a European heat wave in July 2023 that did.

Friederike Otto, another co-author of the study, said heat waves like this will get hotter and more people will die prematurely as long as humans keep burning oil, gas and coal. "The good news is… we know exactly what we need to do and have the technology and knowledge needed to do it — replace fossil fuels with renewable energy, stop deforestation."

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Gordon McBean is a professor emeritus and director for policy at the Institute for Catastrophic Loss Reduction at Western University who recently wrote in The Conversation about how studies that link extreme weather to climate change can help us adapt to a warmer world.

He said being able to link a heat wave like this to climate change while it's still happening may signal to people that "this event is going to be warmer than you've probably gone through" and may help them prepare.

He noted that he's not an expert on climate attribution techniques, but he thinks there are advantages to using different methods and comparing them, as World Weather Attribution has done with its recent studies.

Europe is not the only part of the world that has been hit by heat waves this July — so has much of North America. Extreme heat has been helping wildfires ignite and grow in much of western North America, including B.C., California and Jasper National Park in Alberta. Two global records for the hottest day ever measured were broken one after the other earlier this month. 

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Crews in northern California are trying to contain the Park Fire, now the fifth largest wildfire in the state's history, which grew quickly and forced thousands from their homes.