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The Great Lakes are in an extreme new era
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Caption
Red boxes show the intensity of heat waves, while blue boxes show the intensity of cold spells on Lake Superior, the fastest warming of the Great Lakes, since 1940. Black lines indicate “breakpoints” or significant shifts in trends (similar plots are available for all of the Great Lakes). Credit: Adapted with permission from Abdelhady, H.U., et al. Commun. Earth Environ., 2025, DOI: 10.1038/s43247-025-02341-x (Used under a CC BY 4.0 license)
Heat waves and cold spells are part of life on the Great Lakes. But new research from the University of Michigan shows that is true today in a fundamentally different way than it was even 30 years ago.
“The appearance of these extreme temperatures is increasing,” said Hazem Abdelhady, a postdoctoral research fellow at the U-M School for Environment and Sustainability, or SEAS. “For most lakes, the appearance is up more than 100% compared with before 1998.”
That timing is significant because it coincides with the 1997-1998 El Niño, which is one of the strongest on record, he added.
To reveal this trend, Abdelhady and colleagues developed a state-of-the-art approach to modeling the surface temperature of the Great Lakes, which allowed them to study heat waves and cold spells dating back to 1940.
The surface water temperature of the Great Lakes plays an important role in the weather, which is an obvious concern for residents, travelers and shipping companies in the region. But the uptick in extreme temperature events could also disrupt ecosystems and economies supported by the lakes in more subtle ways, Abdelhady said.
Hot and cold streaks can affect Tribal, recreational and commercial fishing in the Great Lakes, as well as their health and water quality.
Ayumi Fujisaki-Manome and Drew Gronewold of SEAS also contributed to the study.
Study: Climate change-induced amplification of extreme temperatures in large lakes