The results came with a sobering reminder: Once-incomprehensible heat waves are not only happening, but becoming more common.
“They are not rare in today’s climate,” Friedrich Otto, co-chair of the group and a climate scientist at Imperial College London, said in an interview. “What surprises me is that people are so surprised. It’s what we expected.”
It’s not unusual for large swaths of the planet to experience triple-digit temperatures this summer, shattering temperature records, threatening crops and wildlife and posing health risks to billions of people every day.
At least scientifically, Otto said, the findings support a growing consensus among researchers: As the world warms, we are more likely to experience heat waves, stronger storms and other climate-fueled disasters.
Otto and researchers from the United States, the United Kingdom and the Netherlands tried to measure the effect of climate change on heat waves that emerged earlier this month in three regions: the American Southwest and parts of Mexico, southern Europe and part of China.
Using data and simulations that compare the current climate with the past, They examined the periods of July when the heat was most intense in each region — 18 days in parts of the western United States and Mexico, one week in southern Europe and 14 days in the lowlands of China.
Ultimately, they found that the heat waves that hit southwestern and southern Europe were unlikely to occur in a world without climate change. A Chinese heat wave is about 50 times more likely to occur due to global warming, the study found, while European and North American heat waves are at least 1,000 times more likely.
Given the rapid timeline in which the study was completed, the findings have not yet been peer-reviewed, but the team used a set of peer-reviewed methods to describe the climate change fingerprint at each location.
In recent years, the group has been using such methods to identify Dozens Heat waves, extreme rainfall, cyclones, droughts and floods are becoming more frequent or more frequent due to climate change. Some, such as the 2021 Pacific Northwest heat wave that killed hundreds of people, were found to be “virtually impossible” in a world unaltered by greenhouse gas emissions.
This month’s heat waves have been unusual for a long time, and they are becoming more unusual.
Heat waves like the one in Tuesday’s study have a 1 in 15 chance of occurring in any given year in North America, 10 percent in any given year in southern Europe and about 20 percent in any given year in China, the authors said.
In each case, human-caused greenhouse gas emissions warmed the heat wave differently: about 2.5 Celsius (4.5 Fahrenheit) for the European heat wave, 2 Celsius (3.6 Fahrenheit) in North America and 1 Celsius (1.8 Fahrenheit) in China.
The researchers behind Tuesday’s study said they did not specifically examine the role of the El Niño climate pattern that has developed this summer and is known to increase temperatures and alter weather patterns. But they said climate models account for such variations, and any role El Niño plays in land-based heat waves pales in comparison to a warming atmosphere.
“Even though El Niño feeds into the numbers, the signal remains the same,” said Mariam Zakaria, a researcher at Imperial College London and co-author of the study. “The climate change signal is still clear.”
Despite emerging evidence, On display in July, he said, “is how vulnerable our communities are to these changes.”
Already, the group noted, the United States has recorded several heat-related deaths, including among migrants trying to cross the border from Mexico. More deaths have been reported in Spain, Italy and other European countries, as well as in China. Hospital admissions have increased as heat-affected patients seek emergency care, outdoor workers succumb to extreme temperatures and relentless heat has increased demand for electricity.
“This underscores the need for our systems to adapt very quickly because the risks are increasing faster than we can adapt,” Julie Arrighi, director of the Red Cross’s Climate Center, which works to reduce the impacts of extreme weather events on vulnerable populations, told reporters on Monday.
Arrighi said local to national leaders must embrace a “cultural shift” in the way they think about extreme heat and its dangers. As heat waves worsen and become more common, it is important to scale up warning systems, develop programs that provide people with cool places to escape, and strengthen the resilience of power grids, water supplies, and sanitation systems.
In recent years, scientists have said with growing confidence that not only will more extreme weather events be triggered around the planet, but the frequency and intensity of such disasters may worsen over time.
The Intergovernmental Panel on Climate Change (IPCC), a gathering of the world’s leading climate scientists, supported by the United Nations, wrote In its most recent report, “It is almost certain that warm extremes (including heat waves) have become more frequent and more intense over most land areas since the 1950s.”
Meanwhile, the team wrote, the incidence of extreme cold has become “less and less intense.”
In a previous report, the IPCC underlined that episodes of extreme heat around the world would “continue to increase”. Even if humans manage to keep global warming to 1.5 degrees Celsius — the most ambitious goal set out in the 2015 Paris climate agreement — extreme heat events are likely to increase in the future, scientists say.
If the world can’t stop warming the planet, the problem will only get worse over time. “Compared to today’s conditions, changes in extremes would be at least 2 (degrees Celsius) and quadruple global warming by 3 (degrees Celsius), compared to changes of 1.5 (degrees Celsius),” the IPCC wrote.
While not in Tuesday’s study, the warm weather that has enveloped parts of the planet in recent weeks has provided the latest evidence of just how profoundly things are changing.
July may end up being the warmest month on Earth for more than 100,000 years, scientists say. Day by day, records for average global annual temperature are falling.
For most of the month, Phoenix endured daily highs above 11o. Temperatures in one Chinese city reached 126 degrees Fahrenheit. In the Middle East, the heat index reached 152 degrees Fahrenheit, pushing the level considered the most extreme the human body can withstand.
Like past heat waves, like a brutal stretch requested With more than 60,000 lives lost across Europe last summer, the question now is whether policymakers around the world can move quickly — or mobilize resources — to help those most at risk avoid the deadliest form of extreme weather.
“The good news about heat is that we know about a variety of adaptations that can help,” said Jane Baldwin, an assistant professor of geosystems sciences at the University of California, Irvine, who was not involved in Tuesday’s study. “The bad news is that there are still a lot of places where we’re not fully utilizing them.”
Otto is adamant that the startling heat waves of recent weeks, while not uncommon on a warming planet, do not represent a new reality.
“We won’t know what the new normal will be until we stop burning fossil fuels. We’re not in a sustainable climate,” he said.
Unless the trajectory of human emissions is drastically reduced, temperature records will continue to fall. Heat waves grow more intense and prolific, providing only a glimpse of hot stretches.
“This is not what extremes will look like in the future,” Otto said. “It might even be a cold year this coming summer. It’s not something we’re going to get used to. We’re going to have to get used to it, and be worse.
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