Illinois State University’s Catherine O’Reilly is part of a global study that found climate change is rapidly warming lakes around the world, threatening freshwater supplies and ecosystems.

The new study, announced today at the fall meeting of the American Geophysical Union in San Francisco, included more than 60 scientists from across the world, and is set to be published in the journal Geophysical Research Letters.

O’Reilly, an associate professor of geology at Illinois State who is the lead author of the study, calls the findings alarming. “We found that many lakes all around the world are warming much faster than the air or the oceans,” she said. “The study found lakes are warming an average of 0.34 degrees Celsius, or 0.61 degrees Fahrenheit, each decade. That can have profound effects on drinking water and the habitat of fish and other animals.”

Catherine O’Reilly head shot

Catherine O’Reilly

The study, funded in part by NASA and the National Science Foundation, is the largest of its kind, and the first to combine manual lake measurements—made by scientists over more than a century—along with 25 years worth of satellite measurements of lake temperatures. “Manual measurements are mostly done in small lakes, that are generally easy to reach,” said O’Reilly, who noted more than 90 percent of the planet’s lakes are small. “In contrast, satellite images only work if the lake is very big, but they can also gauge temperatures in remote and inaccessible places.”

The study projects that at the current rate, algal blooms—which can ultimately rob water of oxygen—are projected to increase 20 percent in lakes over the next century. And these rates imply that emissions of methane, a greenhouse gas 25 times more powerful than carbon dioxide, will increase four percent over the next decade.

A total of 235 lakes were included in the study. “While that’s a fraction of the world’s lakes, they contain more than half the world’s freshwater supply,” said O’Reilly. She added those numbers are particularly important in the African Great Lakes, home to one-fourth of the planet’s freshwater supply and an important source of fish for food.

“Lakes are our most important source of freshwater,” said O’Reilly. “Until now, we didn’t know on what scale the increase was happening.”

More on the study can be found here.

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