Brutal heatwaves are hitting Europe and the US this week, with scorching temperatures forecast for much of China until the end of August.
In addition to record temperatures, wildfires are raging in southern Europe in cities in Italy and Greece.
According to scientists and climatologists, the increase in temperature caused by human activity is part of global warming.
Hot, frequent heat waves
Climate change is making heat waves hotter and more frequent. This is the case in most land regions, and has been confirmed by the United Nations Intergovernmental Panel on Climate Change (IPCC).
Greenhouse gas emissions have warmed the planet by 1.2 degrees Celsius since pre-industrial times. That warm baseline means extreme temperatures can be reached during extreme heat events.
“Any heat wave we’re experiencing today has been made hotter and longer because of climate change,” said Friedrich Otto, a climate scientist at Imperial College London who leads the World Climate Behavior Research Collaboration.
But other factors affect the heat wave. Air circulation is important in Europe.
A study published this month in the journal Nature found that heatwaves in Europe are three to four times faster than in northern mid-latitudes such as the United States. The authors linked this to changes in the jet stream – a fast west-to-east flow of air in the Northern Hemisphere.
Imprints of climate change
Scientists conduct “scenario studies” to determine exactly how much climate change has affected a particular heat wave. Since 2004, more than 400 such studies have been conducted for extreme weather events, including heat, floods and droughts – calculating how much of a role climate change has played in each.
This involves simulating the modern climate hundreds of times and comparing human-caused greenhouse gas emissions to the climate.
For example, scientists with the World Climate Statement determined that a severe heat wave in Western Europe in June 2019 would have been 100 times more likely to occur in France and the Netherlands if human-induced climate change had not occurred.
The heat wave is still getting worse
Global average temperatures will be around 1.2C warmer than pre-industrial levels. This is already leading to extreme heat events.
“On average, temperature extremes on Earth, which would have occurred once every 10 years without human influence on the climate, are now three times greater,” said Zurich climate scientist Sonia Seneviratne.
Global warming will only stop if humans stop adding greenhouse gases to the atmosphere. Until then, the heat waves are getting worse. Failure to deal with climate change will make temperature extremes more dangerous.
Countries have agreed to limit global warming to 2°C and reduce emissions fast enough to avoid the most dangerous impacts, and to 1.5°C under the global 2015 Paris Agreement. Current policies do not reduce emissions fast enough to meet both goals.
The IPCC says that a heat wave occurring once per decade in the pre-industrial era will occur 4.1 times per decade at 1.5°C warming, and 5.6 times at 2°C.
Allowing warming to exceed 1.5 degrees Celsius means many years “will be affected by warmer extremes in the future,” Seneviratne said.
Climate change causes WILDFIRES
Climate change will increase hotter, drier conditions that help fires spread faster, burn longer, and rage.
In the Mediterranean, that contributed to early rise and burning of more land. More than half a million hectares burned in the EU last year, the worst forest fire in the EU since 2017.
Hot weather helps fire spread by absorbing moisture from vegetation and turning it into dry fuel.
Copernicus senior scientist Mark Parrington said: “The warmer and drier conditions we have now, the more dangerous it is.”
Countries such as Portugal and Greece experience wildfires most of the summer, and have the infrastructure to try to manage them – although both received emergency EU aid this summer. But warmer temperatures are pushing wildfires into regions they’re not used to, so they’re less prepared to deal with them.
Climate change is not the only factor in fires
Forest management and ignition sources are also important factors. More than nine out of 10 fires in Europe are started by human activities such as incinerators, disposable barbecues, power lines or waste glass, according to EU data.
Countries including Spain face the challenge of depopulation in rural areas as people move to cities, clearing vegetation and creating “fuel” for forest fires.
Certain actions can help limit serious fires, such as burning controlled fires that mimic low-intensity fires in natural ecosystem cycles, or introducing gaps in forests to stop large-scale fires.
But scientists agree that heat waves, wildfires, floods and droughts will worsen unless the greenhouse gases that cause climate change are reduced.
“When we look back at the fire in a decade or two, it probably looks relatively simple,” said Victor Resco de Dios, professor of forest engineering at the University of Lleida in Spain.