The fingerprints of climate change are being felt throughout the extreme heat waves sweeping the world this month, a new study finds.
Researchers say the deadly heatwaves in southwestern and southern Europe would not have happened without the continued build-up of greenhouse gases in the air.
Unusually severe heat waves are becoming more common, a study said on Tuesday. The same research found that an increase in greenhouse gases, largely from the burning of coal, oil and natural gas, made another heat wave — the one in China — about 50 times more likely with a probability of occurring every five years or so.
The study found that the stagnant atmosphere, warmed by carbon dioxide and other gases, made the European heat wave 4.5 degrees Fahrenheit (2.5 degrees Celsius) hotter, that of the United States and Mexico 3.6 degrees Fahrenheit (2 degrees Celsius) warmer and those in China 1.8 degrees Fahrenheit (1 degree Celsius) toaster.
Many climatologists, using tree rings and other backup functions for temperature records, say this month’s heat is likely to be the hottest it has been in about 120,000 years, and the hottest in human civilization.
“If there had been no climate change, such an event would not have happened at all,” said the study’s lead author, Mariam Zakaria, a climatologist at Imperial College London. Heatwaves in Europe and North America have been described as “nearly impossible” without an increase in heat since the mid-19th century.
Statistically, it would have happened in China without global warming.
Since the advent of industrial-scale burning, the world has warmed by 2.2 degrees Fahrenheit (1.2 degrees Celsius), so “it’s not rare in today’s climate and the role of climate change is quite overwhelming,” said Imperial College climatologist Frederick Otto, who leads the team of international volunteer scientists at World Weather Attribution who conducted the studies.
Particularly extreme heat waves experienced in Texas, California, Arizona, New Mexico, Nevada, Baja California, Sonora, Chihuahua and Coahuila are likely to occur about once every 15 years in the current climate, the study said.
But the climate is not stable even at this level. If it gets a few tenths of a degree warmer, Otto said, this month’s heat will become more common. Phoenix set a record of 25 days of temperatures at or above 110 degrees Fahrenheit (43.3 degrees Celsius) and more than a week when the nighttime temperature never fell below 90 degrees Fahrenheit (32.2 degrees Celsius).
The study said temperatures in Spain, Italy, Greece and some Balkan countries are likely to recur every decade in the current climate.
Because the weather attribution researchers began their analysis of three simultaneous heat waves on July 17, the results have yet to be reviewed, which is the gold standard for science. But it used scientifically valid techniques, the team’s research is published regularly, and several outside experts told the Associated Press it makes sense.
The way the scientists do these quick analyses, said study co-author Ezidine Pinto, a climatologist at the Royal Netherlands Meteorological Institute, is by comparing observations of current weather in the three regions to repeated computer simulations of “a world that might have been without climate change.”
In Europe and North America, the study does not claim that human-caused climate change is the only cause of heat waves, but rather a necessary component because natural causes and random chance cannot produce this on their own.
The study was reasonable, said Texas climatologist John Nielsen-Gammon, but it looks at a wide area of the southwestern United States, so it may not apply to every place in the region.
“In the United States, it is clear that the entire Southern Hemisphere will experience the worst of ever-increasing temperatures, and this summer should be seen as a serious wake-up call,” said Jonathan Overbeck, dean of the environment at the University of Michigan.
With heat waves, “the most important thing is that they kill people, kill, harm and destroy the lives and livelihoods of those who are most vulnerable,” Otto said.
The Associated Press’s climate and environmental coverage receives support from several private foundations. Learn more about the AP’s climate initiative here. AP is solely responsible for all content.