Lakes across the globe are warming faster than oceans and air temperatures in a sign that climate change may be affecting freshwater environments more than anyone had previously understood.

That’s the finding of a report published in the journal Geophysical Research Letters and announced Wednesday at the fall meeting of the American Geophysical Union.

The study found lakes worldwide warmed an average of 0.61 degrees Fahrenheit per decade between 1985 and 2009.

In northern climates, that increase averaged 1.3 degrees per decade.

“The world’s deepest ice-covered lakes warmed twice as fast as the overlying air temperatures,” the report notes.

Temperature is among the most basic factors in lake ecosystems, the study’s authors noted, and when “the temperature swings quickly and widely from the norm, life-forms in a lake can change dramatically and even disappear.”

The 225 lakes studied in the research, while only a fraction of the world’s total number of lakes, account for more than half of the world’s freshwater supply.

“These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening,” said Catherine O’Reilly, associate professor of geology at Illinois State University and lead author of the report, in a statement released with the report.

More than 60 scientists took part in the research, including University of Minnesota Duluth researcher Jay Austin.

“Several years ago, a couple of us at UMD documented warming trends across the Great Lakes. Other authors have published similar results for individual lakes or sets of lakes around the world,” said Austin. “This study gives credence to the idea that this is a global phenomenon, not just local.”

That’s greater than the warming rate of either the oceans or the atmosphere, and according to the scientists involved, it can have profound effects, eventually reducing the ecosystems’ productivity.

Austin and fellow UMD researcher Steve Colman first announced in 2007 that their research had found that Lake Superior’s average summertime water temperature had risen 4.5 degrees Fahrenheit since 1979, an increase twice as large as what Northland air temperatures had seen in the same period. Moreover, Lake Superior’s rapid temperature rise was among the largest recorded anywhere on Earth.

Authors of the recent study say that if lakes continue to warm at the rate they did during the 25 years studied, algal blooms will increase by 20 percent during the next century. Those blooms rob lakes of oxygen and some can be toxic to fish, animals and even humans.

The trend also will spur more methane production, the study found - worsening the greenhouse gas problem that most scientists say is causing climate change - as well as increased evaporation.

Lakes are critical for humans, not just for recreation, but also for drinking water, irrigation of crops, manufacturing and producing protein - namely fish - said co-author Stephanie Hampton, director of Washington State University’s Center for Environmental Research, Education and Outreach.

The study, funded by NASA and the National Science Foundation, is the largest of its kind and the first to use a combination of long-term hand measurements as well as temperature measurements made from satellites to offset any errors from each method.

The researchers note that in northern climates lakes are losing their ice cover earlier, and many areas of the world have less cloud cover, exposing their waters more to the sun’s warming rays.

Warm-water tropical lakes may be seeing less dramatic temperature increases, but increased warming of these lakes can still have large negative impacts on fish. That can be 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.

Even though the two recent winters have seen vasts areas of ice on the Great Lakes, the long-term trend has been far less ice each winter, Austin noted.

“This study signals the urgent need to take into account this pervasive and rapid warming when looking at vulnerability assessments and adaptation efforts for lakes,” the authors noted.

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