Some of the extreme temperatures recorded earlier in the month in the southwestern United States, southern Europe and northern Mexico were “virtually impossible” without the influence of human-caused climate change, according to research made public Tuesday.
In the first half of July, hundreds of millions of people in North America, Europe and Asia reeled under intense heat waves. Heat waves in China have increased 50 times due to climate change, researchers say.
World Weather Attribution, an international group of scientists measuring how climate change affects extreme weather events, focused on the worst heat ever for a Northern Hemisphere summer. In the United States, temperatures in Phoenix have reached 110 degrees Fahrenheit, roughly 43 Celsius, or more than 20 days in a row. Many places in southern Europe are experiencing record-breaking, triple-digit temperatures. A remote township in China’s Xinjiang has broken a national record by hitting 126 degrees.
“Without climate change, we wouldn’t be seeing this,” said Frederick Otto, senior lecturer in climate science at Imperial College London and co-founder of World Weather Attribution. “Or it’s so rare that it basically doesn’t happen.”
But in a climate altered by fossil fuel emissions, heat waves of this magnitude are “not rare events,” he said.
Before the Industrial Revolution, North American and European heat waves were virtually impossible, according to the researchers’ statistical analysis. China’s heat wave only happens once in about 250 years.
If atmospheric composition remains at today’s levels, the United States and Mexico can expect heat waves this July about once every 15 years. In southern Europe, there is a 1 in 10 chance of a similar event each year. There is a 1 in 5 chance of recurrence each year in China.
But as humans continue to burn fossil fuels and put additional greenhouse gases into the atmosphere, the odds continue to favor extreme heat: Even if we stop, temperatures won’t cool back down, they’ll just stop rising.
“The heat waves we’re seeing now, we’re definitely going to have to live with,” said Dr. Otto said.
As temperatures rise in Europe, Greece has faced a rash of wildfires that have forced the largest evacuation in the country’s history. Officials said the scorching heat made firefighting efforts more challenging. More frequent and more intense wildfires in the Mediterranean are linked to climate change, according to a recent study.
“We have increasing risks from heat,” said Julie Arrighi, director of the Red Cross and Red Crescent Climate Center and one of the researchers on the World Climate Characterization. “It’s deadly.” He emphasized the need to adapt cities and critical infrastructure to extreme heat, while at the same time reducing greenhouse gas emissions.
Many local and national governments, particularly in Europe, have created heat action plans that include public cooling centers and early warning and coordination between social services and hospitals.
But even if these programs exist, they are incomplete, and for now, the human cost of extreme temperatures remains high. The number of heat-related deaths this month has not been clear for some time, but according to the national health secretary, more than 100 people have already died this summer from heat-related causes in Mexico. According to another recent study, last summer, nearly 61,000 people died across Europe due to heat waves.
World Weather Attribution’s heat wave study was not peer-reviewed, but the findings are based on standardized methods published in 2020. The team used twelve climate models to compare real-world observed temperatures with model projections for a planet without human-caused climate change.
“This method is very standard in the field,” said Andrew Pershing, vice president of science at the nonprofit group Climate Central. He was not involved in Tuesday’s study but has previously collaborated with the World Climate Characterization.
The sheer amount of heat that much of the planet is currently experiencing is “shocking” in a historical context, Dr. Pershing said, however, that the findings of climate change’s role were “not surprising.”
The first two weeks of July may have been Earth’s hottest on record, according to an analysis by the European Union’s Copernicus Climate Change Service. The National Oceanic and Atmospheric Administration predicts more unseasonably warm temperatures across the United States in August.
