The results come with a sobering reminder: Once unmeasurable heat waves not only occur, but become more common.
“They’re not uncommon in today’s climate,” said Friederike Otto, team co-leader and climate scientist at Imperial College London. “What surprises me is that people are so surprised. That is exactly what we expected to see.”
It’s not unusual for triple-digit temperatures to persist across large swaths of the planet this summer, breaking temperature records, threatening crops and wildlife and posing health risks to tens of millions of people every day.
Scientifically at least, Otto said, the findings support a growing consensus among researchers: The warmer the world, the more likely regions are to experience crippling heatwaves, stronger hurricanes, and other climate-induced disasters.
Otto and researchers from the United States, United Kingdom, and the Netherlands sought to quantify the impact of climate change on the heat waves that took place earlier this month in three regions: the southwestern United States and parts of Mexico, southern Europe and a large swath of China.
Using data and simulations that compare the current climate with the past, they examined periods during July when the heat was most intense in each region – 18 days in the western United States and parts of Mexico, a week in southern Europe and 14 days in the lowlands of China.
In the end, they found that the heatwaves that scorched southwestern and southern Europe had little chance of occurring in a world without climate change. The study found that heatwaves in China were about 50 times more likely due to global warming, while heatwaves in Europe and North America were at least 1,000 times more likely.
The findings have yet to be peer-reviewed, due to the quick time to complete the study, but the team used a set of peer-reviewed methods to detail the footprint of climate change in each place.
In recent years, the group has used such methods to determine dozens Heat waves, extreme rain, storms, droughts and floods are more likely or more intense due to climate change. Some, such as the 2021 Pacific Northwest heatwave that killed hundreds, are also said to be “virtually unlikely” in a world untouched by greenhouse gas emissions.
Heatwaves this month won’t happen not long ago, but they are becoming less unusual.
Heatwaves like the one in Tuesday’s study now have about a 1 in 15 chance of occurring in any given year in North America, about a 10% chance of occurring annually in Southern Europe, and about a 20% chance of occurring annually in China, the authors said.
In each case, the team found, anthropogenic greenhouse gas emissions made the heatwave hotter than usual: about 2.5 degrees Celsius (4.5 degrees Fahrenheit) hotter for a heatwave in Europe, 2 degrees Celsius (3.6 degrees Fahrenheit) hotter in North America, and 1 degree Celsius (1.8 degrees Fahrenheit) hotter in China.
The researchers behind Tuesday’s study said they did not specifically examine the role of El Niño climate patterns that have developed this summer and are known to increase temperatures and change weather patterns. But they say climate models account for such variations, and that any role El Niño plays in land-based heatwaves pales in comparison to the role of the warming atmosphere.
“Although El Nino passed in the numbers, the signal stayed the same,” said Mariam Zachariah, a researcher at Imperial College London and study co-author. “Climate change signals are still clear.”
Despite emerging evidence, What was on display in July, she said, “is how vulnerable our society is to these changes.”
The group noted that the US has recorded many heat-related deaths, including migrants trying to cross the border from Mexico. Other deaths have been reported across Spain, Italy and other European countries, as well as in China. Hospitalizations have increased as heat-affected patients seek urgent care, outdoor workers succumb to the scorching heat, and the relentless heat has caused electricity demand to spike.
Julie Arrighi, director of the Red Cross’s Red Crescent Climate Center, which works to reduce the impact of extreme weather events on vulnerable people, told reporters on a call on Monday: “It underscores the need for our systems to adapt much faster, because the risks are growing much faster than we can.
Arrighi said leaders from the local to the national level must accept a “cultural shift” in the way they think about extreme heat and its dangers. As heat waves worsen and become more common, it’s important to scale up warning systems, develop plans that give people cool places to escape, and strengthen the resilience of power grids, water supplies, and health systems.
In recent years, scientists have increasingly confidently asserted that not only are humans driving more intense extreme weather events across the planet, but that the frequency and severity of such disasters are likely to get worse over time.
The Intergovernmental Panel on Climate Change (IPCC), a United Nations-backed gathering of some of the world’s leading climate scientists, Written in its most recent report that “it is almost certain that extreme heat waves (including heat waves) have become more frequent and more intense over most of the mainland since the 1950s.”
Meanwhile, the panel wrote, extreme cold cases “have become less frequent and less severe”.
In an earlier report, the IPCC emphasized that extreme heat waves “will continue to increase” globally. Scientists say that even if humans try to keep the Earth’s warming to no more than 1.5 degrees Celsius – the most ambitious goal set out in the 2015 Paris climate accord – extreme heat events will proliferate in the near future.
If the world can’t stop warming the planet, the problem is likely to get worse over time. “Compared with today’s conditions, changes in the intensity of extremes would be at least twofold at 2 (degrees C) and quadruple at 3 (degrees C) of global warming, compared with changes at 1.5 (degrees C),” the IPCC wrote.
Even without Tuesday’s study, the scorching hot weather that has engulfed parts of the planet in recent weeks offers the latest evidence of how profoundly things are changing.
Scientists have said that July is likely to become the hottest month on record on Earth, and possibly for another 100,000 years. Day after day, records for the annual average global temperature have been falling.
For most of the month, Phoenix maintained a daily high above 11o. The temperature in one Chinese town reached 126 degrees Fahrenheit. In the Middle East, the heat index reached 152 degrees Fahrenheit, pushing what is said to be the most intense that the human body can withstand.
As in previous heat waves, such as the brutal stretch that declare With more than 60,000 lives lost across Europe last summer, the question is whether policymakers around the world can act fast enough — or can muster resources — to help those most at risk avoid the deadliest form of extreme weather.
“The good news about heat is that we’re aware of the many different ways adaptations can be helpful,” said Jane Baldwin, assistant professor of Earth system science at the University of California at Irvine who was not involved in Tuesday’s study. “The bad news is that there’s still a lot of space we haven’t taken advantage of.”
Otto is adamant that the astonishing heat waves of recent weeks, while no longer uncommon on a warming planet, do not represent a new reality.
“We don’t know what the new normal is until we stop burning fossil fuels. “We are not in a stable environment,” she said.
Until the trajectory of human emissions plummets, temperature records will continue to fall. Heat waves will become more intense and more frequent, giving us only a glimpse of the potential for more heat ahead.
“These are not future extremes,” said Otto. “This could even be a cold year in the coming summers. This is not what we need to get used to. We need to get used to this, and worse.”
