The extreme heat blanketing the southern regions of the U.S., Mexico, and Europe this month would have been nearly impossible without the warming effects of human-induced climate change, according to a study released Tuesday by a group of European scientists who carry out rapid assessments of extreme weather events.
The study by World Weather Attribution, a group of researchers based in London and the Netherlands, found that three separate heat waves in July across the Northern Hemisphere were made much worse because of decades of fossil-fuel emissions that have raised the planet’s average temperature by 2 degrees Fahrenheit since the late 19th century.
“It’s something that we definitely will see more of in the future,” said Friederike Otto, co-founder of World Weather Attribution, an author on the new study and a senior lecturer in climate science at the Grantham Institute in London. “We don’t know what the new normal or the new extreme will be in the future because we don’t know when we will stop burning fossil fuels.”
The study hasn’t been peer-reviewed, which is considered the gold standard for validating research findings; however, it is based on peer-reviewed methods the group published in 2020.
To assess the recent heat waves, the scientists ran a dozen climate models comparing the temperatures observed this month with projections of a similar world without climate warming. They concluded that without human-induced climate change, the extreme heat in China would have been about a one-in-250-year event, while the heat waves in July in the U.S., Mexico, and southern Europe would have been virtually impossible.
For the past few years, global temperatures have been moderated by the cooling effects of a three-year La Niña weather pattern in the Pacific Ocean. Now, the Pacific is switching to its opposite pattern, known as El Niño, which brings warm water to the eastern Pacific and influences weather patterns across the globe.
Last month was the world’s hottest June in the 174-year global climate record tracked by the National Oceanic and Atmospheric Administration. U.S. officials said recently that the first week of July was the hottest globally since record-keeping began in 1850, and expect the entire month will be the hottest ever, surpassing the previous hottest month of July 2016.
“We anticipate that July is likely to be the warmest absolute month on record, and that’s going to be a record that effectively goes back many hundreds if not thousands of years,” said Gavin Schmidt, director of the National Aeronautics and Space Administration’s Goddard Institute for Space Studies in New York, during a press call last week. “We don’t see this every year.”
Climate scientists have a good understanding of temperatures before record-keeping based on so-called proxy measures, which include the thickness of tree rings, lake and ocean sediments that record pollen from plants, ice cores taken from glaciers and ice sheets, corals, fossils and records from ship logs and early weather observers, according to NOAA.
July’s extreme heat affected over 100 million people across the U.S. and dozens of people have suffered heat-related deaths along the border with Mexico and throughout Arizona, the study said. More than 200 heat-related fatalities have been reported in Mexico, half in the northern state of Nuevo Leon, the study said.
Phoenix has suffered under 25 straight days of 110-degree-plus heat, a record for the city, forcing construction workers to pour concrete at night and cool materials with buckets of ice.