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Posted on December 16, 2015

Dr. Derek Gray on a boat on a riverDr. Derek Gray, an assistant professor in Cal U’s Department of Biological and Environmental Sciences, is a key contributor to a global study that finds climate change is rapidly warming the world’s lakes, threatening freshwater supplies and aquatic ecosystems.

The study’s findings were announced Dec. 16 at the fall meeting of the American Geophysical Union. With nearly 24,000 attendees, it is the world’s largest Earth and space science meeting.

An international cohort of more than 60 scientists contributed to the study of lake temperatures. Gray was a lead participant in the data analysis phase and one of four co-authors of a report slated for publication in the journal Geophysical Research Letters.

“Fresh water is one of our most vital resources,” said Gray, who noted that lakes are important sources of water for drinking, irrigation, energy and food production. “Yet this is one of the first studies to take a worldwide, long-term look specifically at lakes.”

About the study

Funded in part by NASA and the National Science Foundation, the study is the largest of its kind and the first to use a combination of satellite temperature readings and measurements taken manually at lakes around the world.

Gray and his fellow researchers assembled and analyzed a massive database of temperature readings for 235 lakes and reservoirs — more than half the world’s freshwater supply — between 1985 and 2009.


The study reveals that lakes are warming an average of 0.61 degrees Fahrenheit each decade, more than the warming rate of either the oceans or Earth’s atmosphere.

Warming fastest are lakes in the northern latitudes that typically ice over during the winter.

“The ice is breaking up earlier every year,” said Gray, whose postdoctoral research examined the impacts of climate change on Lake Baikal, in Siberia.

“In fact, some of the ice-covered lakes are warming even more rapidly than the air around them.”

The study also points to a significant increase in algal blooms — the rapid and sudden growth of microscopic algae — that over the next century may have harmful effects on both water quality and aquatic life, including fish harvested for food.

The researchers forecast a 4 percent increase worldwide in lakes’ emission of methane, a potent greenhouse gas implicated in global warming, over the next decade. And as lake water warms, evaporation increases and water levels decline, making less fresh water available for human use.

“This study shows that warming of lakes already has begun, with potentially serious consequences,” Gray said.

“Ultimately, water security is an issue that affects us all.”