Prolonged and expansive heat waves have altered daily life in Europe, causing train cancellations and transforming typically verdant terrain into yellowed lands.
Although heat waves are stoked by a confluence of weather events like the behavior of winds high up in the atmosphere, the rise in global temperatures spurred on by human-caused climate change has given heat waves -- including this one -- a potent boost.
"It’s safe to say as the world is warming up, we shouldn’t be surprised we’re going to get these extreme heatwaves here [United Kingdom], and all over the world," Ed Hawkins, a climate scientist at the University of Reading in the UK, said in an interview.
In 1976, Hawkins noted the UK experienced a famously brutal summer heat wave, during the nation's hottest summer on record. This summer, however, the UK is not alone.
Algeria, Japan, Scandinavia, the Western U.S., and other regions have all been hit by record-breaking, extreme heat.
"It’s an increase in heat waves that is very stark and noticeable," said Hawkins.
And in the higher-latitude UK, where recent temperatures as high as 95 degrees Fahrenheit (35 Celsius) are extreme, the effects are visible and palpable.
"All the grass is brown and we’re having problems on the railways as well because the tracks get too hot," Hawkins added. "People are struggling in [overheated] buildings and are working outside."
In the last 40 years, Earth has experienced an accelerating warming trend, which NASA scientists have been watching closely. Overall, in the last 150 years, the globe's average temperature has increased by 1 degree Celsius (1.8 degrees Fahrenheit).
While that might not sound like much, it is.
"That's actually a lot," Michael Wehner, a senior scientist at the U.S. Department of Energy's Lawrence Berkeley National Laboratory, said in an interview.
"We have a background of 1 degree Celsius," said Wehner, who researches how different weather events are influenced by climate. "That would make any heat wave, on any part of the planet, hotter than it would normally be."
"I’m virtually certain that nearly all heatwaves have been made more severe by climate change"
These days, when it comes to heat waves, rising global temperatures are almost always a factor, he said.
"I’m virtually certain that nearly all heat waves have been made more severe by climate change," said Wehner.
Other major weather influences may be changing too, further exacerbating heat waves, like the one in Europe.
Specifically, there's growing evidence that the jet stream -- powerful jets of wind some 30,000 to 45,000 miles above the Earth's surface that steer weather around the globe -- may be getting stalled over certain places for longer periods of time, Jennifer Francis, a scientist at Rutgers University's Department of Marine and Coastal Sciences, said in an interview. This can jam up weather traffic, keeping either storms or domes of heat suspended over large regions.
Additionally, the jet stream can split, Francis said, allowing weather patterns, like blocks of hot air, to "stagnate" between these strong air currents.
"This implies that these persistent heat waves will happen more in the future," she said.
While it can be difficult to attribute some weather events, like hurricanes, to human-caused climate change, the case is much clearer when it comes to heat waves.
"We’re past that point where, according to our analysis, you would have a heat wave where you wouldn’t expect some human influence," said Wehner.
A decade ago, it would have been challenging to say if a particular heat wave might have been influenced by the warming climate, Wehner pointed out.
"But that's not true now," he said.
