In addition to temperatures soaring above 40 degrees Celsius (104 degrees Fahrenheit), wildfires are raging across southern Europe with evacuations in cities in Italy and Greece.
The scorching heat is part of a global pattern of warming, which scientists attribute to human activity.
Climate change is making heat waves hotter and more frequent. This is the case for most regions of the Earth, and has been confirmed by the United Nations International Panel of Climatologists (IPCC).
Greenhouse gas emissions from human activities have warmed the planet by about 1.2°C since pre-industrial times. This warmer baseline means that higher temperatures can be reached during extreme heat events.
“Every heat wave we’re seeing today is getting hotter and more frequent because of climate change,” said Frederic Otto, a climate scientist at Imperial College London who is also co-leading the global weather attribution research collaboration.
But there are other conditions that affect heat waves as well. In Europe, atmospheric circulation is an important factor.
A study published in Nature this month found that heat waves in Europe increased three to four times faster than in other northern mid-latitudes such as the United States. The authors relate this to changes in the jet stream – a rapid west-to-east air current in the Northern Hemisphere.
To find out how climate change affects a particular heat wave, scientists conduct “attribution studies”. Since 2004, more than 400 such studies of extreme weather events, including heat, floods and droughts, have been conducted to calculate how much of a role climate change plays in each.
This involves simulating modern climate hundreds of times and comparing it to simulating a climate without human-caused greenhouse gas emissions.
For example, scientists using the World Weather Attribution determined that a record-breaking heat wave in Western Europe in June 2019 was now 100 times more likely to occur in France and the Netherlands than if humans had not changed the climate.
Heat waves will continue to worsen
Global warming is already driving extreme heat events.
“On average on Earth, temperature extremes that would have occurred once every 10 years without human influence on the climate are now three times more frequent,” said Sonia Seneviratne, a climate scientist at the European Institute of Technology in Zurich.
Temperatures will only stop rising if humans stop adding greenhouse gases to the atmosphere. Until then, heat waves will only get worse. Failure to tackle climate change will cause extreme temperatures to rise even more dangerously.
Countries agreed under the 2015 Paris global agreement to cut emissions fast enough to limit global warming to 2°C, and aim for 1.5°C, to avoid its most dangerous effects. Current policies will not reduce emissions fast enough to achieve either goal.
The Intergovernmental Panel on Climate Change says that the once-per-decade heat wave in the pre-industrial era will occur 4.1 times per decade at 1.5°C, and 5.6 times at 2°C.
Allowing 1.5°C of warming to pass means that most years will be “affected by hot events in the future,” Sniferatne said.
Climate change is causing wildfires
Climate change is increasing hot, dry conditions that help fires spread faster, burn longer, and become more intense.
In the Mediterranean, this contributed to the fire season starting early and burning more land. Last year, more than half a million hectares of land burned in the European Union, making it the second worst bushfire season in the Union after 2017.
Hot weather also drains moisture from vegetation, turning it into dry fuel that helps fires spread.
“The hottest driver conditions right now, make it even more common. [fires] It’s more serious, said Mark Barrington, Copernicus’ chief scientist.
Countries like Portugal and Greece suffer from fires for most of the summer, and have the infrastructure to try to manage – despite both receiving emergency help from the European Union this summer. But higher temperatures also push wildfires into areas they are unfamiliar with, and therefore less prepared to deal with.
Forest management and ignition sources are also important factors. In Europe, more than nine out of 10 fires are ignited by human activities, such as arson, single-use barbecues, power lines or scattered glass, according to EU data. But the climate crisis usually creates conditions that make the effects of these fires much worse.
Countries, including Spain, face the challenge of a shrinking rural population, as people move to the cities, leaving the smaller workforce to clear vegetation and avoid the “fuel” of the bushfire buildup.
Some actions can help reduce intense fires, such as controlled fires that mimic low-intensity fires in natural ecosystem cycles, or inserting gaps within forests to stop fires from spreading rapidly over large areas.
But scientists agree that without sharp cuts in the greenhouse gases that cause climate change, heat waves, wildfires, floods and droughts would only get exponentially worse.
“When we look back at the current fire season in a decade or two, it probably looks moderate by comparison,” said Victor Risco de Dios, professor of forest engineering at Spain’s University of Lleida.