The Washington PostDemocracy Dies in Darkness

The European heat wave bears the fingerprint of climate change

Placeholder while article actions load

The extraordinary heat wave that is gradually relinquishing its hold on Western Europe will enter the history books as one of the most intense such extreme events on record. The benchmarks it set in countries such as the United Kingdom, Belgium, Germany and the Netherlands are extraordinary.

To climate scientists, they’re also part of a disturbing pattern that’s likely to be repeated more often.

Researchers say that what is important to look at is not how many records were toppled. It’s by how much they were broken, or in this case, obliterated, that matters. Usually when a new all-time temperature record is set, it beats the old one by a few tenths of a degree. But not this time.

This heat wave featured multiple all-time records that were broken by several degrees.

For example:

  • In France, Paris set an all-time record temperature of 108.7 degrees on Thursday. The previous record was 104.7 degrees set in June 1947. This means Thursday’s temperature surpassed the 72-year-old record by an astonishing four degrees. Similarly, Lille set an all-time record temperature of 106.5 degrees on Thursday, smashing its previous record — set last year — by seven degrees.
  • Germany set a national temperature record when a sensor in Lingen measured 108.7 degrees on Thursday, eclipsing the old record, set just the previous day, by 3.8 degrees.
  • Belgium set a national record of 107.2 degrees on Thursday in Begijnendijk. According to Meteo-France forecaster Etienne Kapikian, this beat the previous Belgium record by an astonishing 6.1 degrees.
  • The Netherlands set a national record high temperature of 107.1 degrees on Thursday. The previous record was 101.8, set in August 1944. That’s a difference of 5.3 degrees. According to the Royal Netherlands Meteorological Institute, none of their sensors had ever ticked above 104 degrees before.

What makes this heat wave stand out

Heat of this magnitude is impressive. But a heat wave demolishing records by such an obscene margin over such a large area? Virtually unprecedented. “Some of these records were not beaten by a small increment,” wrote J. Marshall Shepherd, director of the University of Georgia’s atmospheric sciences program, in an email. “They established an entirely new baseline.”

Shepherd likens the significance of beating a record by five or even six degrees to having a dangerous fever. “If you have temperature of 99.6 degrees, it is alarming,” he said, and 103 degrees “would send you right to the doctor.”

According to University of Oklahoma meteorology professor Jason Furtado, “the degree by which the records were broken is astounding.”

Climate scientists can connect changes in the frequency and magnitude of extreme events to human-caused climate change.

World Weather Attribution, an international scientific collaboration dedicated to exploring the link between extreme weather events and climate change, recently released a preliminary report concerning a previous, though less intense, European heat wave in late June and early July.

“Every heat wave occurring in Europe today is made more likely and more intense by human-induced climate change,” the study concluded. “The observations show a very large increase in the temperature of these heat waves.”

Even a seemingly small shift in the global average temperature can spur disproportionately large changes in the likelihood and intensity of temperature extremes. Our heat-trapping emissions are doing it in two ways: by altering both the mean and variance of temperatures.

Mean describes the average of a quantity. In the case of global average temperatures, that mean has risen about 1.8 degrees over the past century, according to Berkeley Earth. That subtle nudge of temperature distributions disproportionately increases the likelihood of top-tier extreme heat. And it doesn’t stop there.

Human behavior is also increasing the variance of our climate. Variance characterizes the variability or “spread” of a quantity. By increasing the variance of our climate, we “nudge” the extremes further and further from the more “normal” zones in the middle. That also increases the probability of ending up with an extreme event.

Coupled together, these two effects are already having dire consequences, given that extreme heat can be deadly. Oftentimes, these deaths go unreported in the media, as it takes months to analyze how and to what extent heat may have played a role in any fatalities. A similar European heat wave in 2003 is estimated to have killed 70,000.

“The verdict is in: Increasing greenhouse gas concentrations due to human activity — by raising average temperatures — have loaded the dice toward more frequent record breaking heat extremes (like this event),” wrote Radley Horton, a climate researcher at Columbia University, in an email. “But the magnitude with which all-time records are being broken — [four degrees] for Paris — suggests an accomplice. Specifically, human-driven increases in the variability of our day-to-day weather.”

Heat waves will happen with or without humans. But we’re altering their characteristics in ways that make it harder for humans to cope with them. Shepherd wrote a piece in Forbes comparing human activity to a “performance-enhancing drug” for the climate.

Meanwhile, the dome of heat plaguing Western Europe is on its way out, offering some much-needed relief for the beleaguered region. But we’re far from finished seeing the impacts from the system behind the massive heat wave. In the coming days, that system is set to target the Arctic.

Europe’s heat wave is about to bake the Arctic