In addition to temperature spikes above 40 degrees Celsius (104 Fahrenheit), wildfires are raging across southern Europe with cities in Italy and Greece evacuated.
The searing heat is part of a global pattern of rising temperatures that scientists attribute to human activity.
Climate change is making heat waves hotter and more frequent. This applies to most land regions and has been confirmed by the United Nations Global Panel of Climatologists (IPCC).
Greenhouse gas emissions from human activity have warmed the planet by about 1.2 degrees Celsius since pre-industrial times. This warmer baseline means that higher temperatures can be reached during heat extremes.
“Every heatwave we experience today has been getting hotter and more frequent due to climate change,” said Friederike Otto, a climatologist at Imperial College London who is also one of the leaders of the World Weather Attribution research collaboration.
But other conditions also affect heat waves. In Europe, atmospheric circulation is an important factor.
A study published in the journal Nature this month found that heatwaves in Europe are increasing three to four times faster than in other northern mid-latitudes such as the United States. The authors attribute this to changes in the jet stream, the fast airflow from west to east in the northern hemisphere.
To find out exactly how much climate change has affected a particular heatwave, scientists are conducting “attribution studies.” Since 2004, more than 400 such studies of extreme weather events, including heat waves, floods and droughts, have been conducted to estimate the role climate change has played in each.
This includes modeling the current climate hundreds of times and comparing it to climate simulations without anthropogenic greenhouse gas emissions.
For example, scientists from World Weather Attribution have determined that a record heat wave in Western Europe in June 2019 is 100 times more likely now in France and the Netherlands than if people had not changed the climate.
Heat wave will continue to intensify
Global warming is already causing extreme heat events.
“On average, on land, extreme temperatures that would occur once every 10 years without human influence on the climate now occur three times more often,” said ETH Zurich climatologist Sonya Seneviratne.
Temperatures will stop rising only if people stop emitting greenhouse gases into the atmosphere. Until then, the heat will continue to rise. If the problem of climate change is not addressed, extreme heat will become even more dangerous.
Under the 2015 global Paris Agreement, countries agreed to cut emissions fast enough to limit global warming to 2°C and aim for 1.5°C to avoid its most dangerous effects. The current policy will not cut emissions fast enough to meet any target.
According to the IPCC, a heatwave that occurred once per decade in the pre-industrial era would occur 4.1 times per decade for 1.5°C warming and 5.6 times per decade for 2°C warming.
If warming exceeds 1.5°C, Seneviratne said, it means that most years “will be affected by extreme hot events in the future.”
Climate change leads to forest fires
Climate change exacerbates hot and dry conditions, which contribute to faster spread of fires, longer burning and more intense raging.
In the Mediterranean, this contributed to the fire season starting earlier and burning more land. More than half a million hectares burned in the European Union last year, making this wildfire season the second worst in the bloc’s history after 2017.
Hotter weather also drains moisture from vegetation, turning it into dry fuel that helps fires spread.
“Right now, hotter, drier conditions are making [fires] much more dangerous,” said Mark Parrington, senior researcher at Copernicus.
Countries like Portugal and Greece have fires for most of the summer and have the infrastructure to try to deal with them, although both countries received emergency EU aid this summer. But warmer temperatures are also causing wildfires in regions that are not used to them and therefore less prepared to deal with them.
Forest management and sources of ignition are also important factors. More than nine out of 10 fires in Europe are caused by human activities, such as arson, disposable barbecues, power lines or clogged glass, according to the EU. But the climate crisis usually creates conditions that greatly exacerbate the effects of these fires.
Countries, including Spain, are facing depopulation in rural areas as people move to cities, leaving a smaller workforce to clear vegetation and avoid fuel for wildfires.
Some actions can help limit the extent of large fires, such as building controlled fires that mimic low-intensity fires in natural ecosystem cycles, or creating gaps in forests to stop wildfires from spreading quickly over large areas.
But scientists agree that without drastic cuts in greenhouse gas emissions that cause climate change, heat waves, wildfires, floods and droughts will get much worse.
“When we look back at the current fire season in one or two decades, it will probably seem moderate by comparison,” said Victor Resco de Dios, professor of forest engineering at the Spanish University of Lleida.