Record-breaking heat waves in US and Europe prove climate change is already here, experts say

Hundreds of millions of people around the world are currently experiencing sweltering, dangerous heat -- a new reality as the effects of climate change continue to manifest in severe weather events of every kind.

A scorching airmass remains over the majority of the continental U.S. on Wednesday, with a heat dome sitting over the Southwest and Great Plains and triple-digit temperatures stretching throughout the Midwest and up and down the East Coast.

While Wednesday brought slight relief to Europe with its own block of boiling weather that helped to reach the hottest temperature ever recorded in London, there were wildfires across the continent and more than 1,500 heat-related deaths in Spain and Portugal alone.

The predictions climate scientists have been making for decades about what awaited the planet should the temperatures continue to rise are currently coming into fruition in the form of these heat waves that are occurring concurrently in lands thousands of miles apart, experts told ABC News.

The "most direct" connections between weather and climate change are the increase in intensity, frequency, duration and expanse of heat waves, said Jennifer Francis, senior scientist at the Woodwell Climate Research Center. And "even stronger extremes" are expected in the future, World Meteorological Organization Secretary-General Petteri Taalas said during a press conference Tuesday.

Extreme heat is a "basic consequence of climate change," and the fact that it's happening in several different locations at the same time is characteristic of the average global temperatures rising, Jason Smerdon, a climate scientist for the Columbia Climate School's Lamont-Doherty Earth Observatory in New York, told ABC News.

"While each heat wave itself is different, and has individual dynamics behind it, the probability of these events is a direct consequence of the warming planet," Smerdon said, adding that a break in low airmass off the Atlantic Ocean moved east and blanketed Spain and Portugal, which is why those countries experienced the worst of the prolonged heat.

Historically, when records are broken, they are done so in very small increments, such as a fraction of a degree -- another characteristic that makes the current heat waves much more severe than in years past, Smerdon said. The previous record in the U.K. occurred at the Cambridge Botanic Gardens at 101.6 degrees Fahrenheit in July 2019. On Tuesday, that record was broken when the temperature measured at 104 F -- a hallmark that the Earth's climate is currently in "uncharted territory," Francis said.

"These things are blowing the roof off of the previous record," Smerdon said, adding that the same applies to the record-breaking heat waves that occurred in the Pacific Northwest last year. Those heat waves would have been "virtually impossible" without climate change, a study published in 2021 found.

If the Earth were in "normal times," there would be an even distribution between low-temperature and high-temperature records being broken, Francis said.

The fact that Britain, which is essentially at the same latitude as Calgary in Canada, is experiencing triple-digit temperatures at such frequency poses a danger to human health because the majority of the infrastructure was built during a century that never saw such heat, Smerdon said. A large portion of the population is not equipped with air conditioning in their homes, and therefore are not able to cool off all the heat exhaustion that built up during the day, Rachel Licker, principal climate scientist at the Union of Concerned Scientists, told ABC News. The heat is also colliding with other climate hazards, such as the wildfires in Spain and the poor air quality that comes with it, she added.

Look to the Arctic for another explanation as to why extreme heat will occur more often, the experts said. Because the North Pole is warming faster than the rest of the planet, therefore reducing the difference in temperature between the equator and the North Pole, it's shifting the atmospheric patterns of the jet stream, the band of strong winds created by cold air meeting warmer air that moves west to east and drives many weather patterns around the globe, Smerdon said.

There is research to suggest that the pattern of the jet stream in the northern hemisphere is becoming more wavy due to the melting Arctic, which would increase the possibility of "pumping a tremendous amount of heat up into western and northern Europe," Smerdon said.

The weakening jet stream can also be blamed for the extreme cold that reaches southern states that normally do not experience freezing temperatures, such as the freeze that struck Texas in February 2021, knocking out the power grid and leaving millions in the cold.

One of the reasons temperatures in western Europe heated up so quickly was the combination of the dry soil, changes in the jet stream and high-pressure airmass that stalls over one place over a long period of time, Sjoukje Philip, a researcher at the Royal Netherlands Meteorological Institute, said in a statement on Friday.

Temperatures reaching up to 50 degrees Celsius, or 122 degrees Fahrenheit, are not out of the realm of possibility in the coming decades if greenhouse gas emissions are not reduced to zero, Robert Vautard, director of the Dynamic Meteorology Laboratory at Sorbonne University in Paris, said in a statement last week.

"We know such a jump is possible," Vautard said.

Despite decades of research that projected these heat events, scientists are not immune to worrying about the state of global warming as they watch these heat waves disrupt the daily lives of so many millions of people, Licker said.

"There are all of these different segments of society that are particularly vulnerable to extreme heat," such as the elderly and outdoor workers, she said.

The "silver lining" of these heat waves may be the wakeup call that the government and industries need to really focus on reducing carbon footprints in the next decade, Francis said, adding, "We don't have much time left."

Climate scientists will now be tasked with answering more prevailing questions, such as whether there are amplifying features they are missing in their predictions.

"Is there a potential that we've under-predicted the magnitude of these extreme events because of subtle features in the climate system that we haven't characterized, adequately?" Smerdon said of the immediate future of climate research.