Earth's worst heat waves of recent decades didn't happen when you think they did

A recent study found that the worst heatwaves in known history took place decades ago.
A recent study found that the worst heatwaves in known history took place decades ago. (Image credit: Bloomberg/Getty Images)

Despite the impact of climate change on Earth, the worst heat waves on our planet aren't happening now. They actually occurred 40 years ago, a new study has found.

The summer of 2021 may have brought the highest recorded temperatures to swaths of the American Northwest. When compared to local averages, however, this devastating heat wave loses out to hot spells that took place about 40 years ago in other parts of Earth, according to a review by researchers from the University of Bristol in the United Kingdom.

For example, the 1985 heat wave in Brazil, which peaked at temperatures of 97.7 degrees Fahrenheit (36.5 degrees Celsius), and the 1980 heat wave that struck the American South with temperatures of up to 101 degrees F (38.4 degrees C), were both more severe when compared to local averages than the 2021 heat wave in the American Northwest, the scientists said in a statement. The 1998 heat wave in Southeast Asia, with temperatures hitting 91 degrees F (32.8 degrees C), was also relatively more intense, despite the fact that last year, temperatures in British Columbia, Canada, hit a much higher record of 121 degrees F (49.6 degrees C). The average temperature of Earth is about 57 degrees F(13.9 degrees C).

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"The recent heat wave in Canada and the United States shocked the world," Vikki Thompson, a climate scientist at the University of Bristol and lead author of the new paper said in a statement. "Yet we show there have been some even greater extremes in the last few decades."

The authors said that the global public may have paid less attention to some of the earlier heat waves because they took place in developing countries. 

"Climate change is one of the greatest global health problems of our time, and we have shown that many heat waves outside of the developed world have gone largely unnoticed," said Dann Mitchell, Professor in Climate Sciences at the University of Bristol and co-author of the paper. "The country-level burden of heat on mortality can be in the thousands of deaths, and countries which experience temperatures outside their normal range are the most susceptible to these shocks."

Last year's heat wave in western North America was the deadliest in Canadian history, the researchers said in the statement, causing hundreds of fatalities and widespread destruction through wildfires. 

Thompson added that models suggest that the progressing climate warming is likely to increase the magnitude of heat waves over the next 100 years. 

The study was published in the journal Science Advances on Wednesday (May 4).

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Tereza Pultarova
Senior Writer

Tereza is a London-based science and technology journalist, aspiring fiction writer and amateur gymnast. Originally from Prague, the Czech Republic, she spent the first seven years of her career working as a reporter, script-writer and presenter for various TV programmes of the Czech Public Service Television. She later took a career break to pursue further education and added a Master's in Science from the International Space University, France, to her Bachelor's in Journalism and Master's in Cultural Anthropology from Prague's Charles University. She worked as a reporter at the Engineering and Technology magazine, freelanced for a range of publications including Live Science,, Professional Engineering, Via Satellite and Space News and served as a maternity cover science editor at the European Space Agency.