More than 60 scientists including Dr Linda May from the Centre for Ecology & Hydrology took part in the research, published in the journal Geophysical Research Letters.
The study found lakes are warming an average of 0.34 degrees Celsius each decade. That’s greater than the warming rate of either the oceans or the atmosphere, and it can have profound effects, the scientists say.
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. Algal blooms that are toxic to fish and animals would increase by five percent. 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.
“Lakes are important because society depends on surface water for the vast majority of human uses,” said co-author Stephanie Hampton, director of Washington State University’s Center for Environmental Research, Education and Outreach. “Not just for drinking water, but manufacturing, for energy production, for irrigation of our crops. Protein from freshwater fish is especially important in the developing world.”
A total of 235 lakes were monitored for at least 25 years. While that’s a fraction of the world’s lakes, they contain more than half of the world’s freshwater supply. Loch Leven, one of CEH’s most important long-term monitoring sites, was part of the study.
“At Loch Leven, the only UK lake included in the study, average summer surface water temperatures are increasing by 0.75 degrees per decade, making it one of the fastest warming lakes in the world. We have already noticed some of the effects of this on a year-to-year basis, with much less ice cover occurring in recent years than in the 1980s.” said co-author Linda May. “This change is likely to affect water quality, with algal blooms becoming more common during the summer months. This could affect its value as a water resource and limit its recreational use in years to come. The widespread evidence that we have found of lake warming across the globe, suggests that large changes are not only imminent, but already underway.”
"At Loch Leven, average summer surface water temperatures are increasing by 0.75 degrees per decade, making it one of the fastest warming lakes in the world." Dr Linda May, CEH
In general, the researchers write, “The pervasive and rapid warming observed in these lakes signals an urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts.”
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 long-term hand measurements and temperature measurements made from satellites, offsetting the shortcomings of each method.