Climate change is rapidly warming lakes around the world, threatening freshwater supplies and ecosystems, a new global study led by an Indian-origin researcher has warned.
The study is the largest of its kind and the first to use a combination of satellite temperature data and long-term ground measurements.
"We found that lakes are warming at an average of 0.34 degrees Celsius each decade all around the world, threatening freshwater supplies and ecosystems," said Professor Sapna Sharma from York University in Toronto.
"This can have profound effects on drinking water and the habitat of fish and other animals," said Sharma, lead author of the study
For the study funded by NASA and the National Science Foundation in US, 235 lakes, representing more than half of the world's freshwater supply, were monitored for at least 25 years.
The study found that lakes are warming at an average of 0.34 degrees Celsius each decade. That is greater than the warming rate of either the ocean or the atmosphere and can have profound effects, researchers said.
Algal blooms, which can ultimately rob water of oxygen, are projected to increase 20 per cent in lakes over the next century as warming rates increase. Algal blooms that are toxic to fish and animals would increase by 5 per cent.
If these rates continue, emissions of methane, a greenhouse gas 25 times more powerful than carbon dioxide on 100-year time scales, will increase 4 per cent over the next decade.
"Society depends on surface water for the vast majority of human uses," said Stephanie Hampton from Washington State University.
"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," she added.
The temperature of water influences a host of its other properties critical to the health and viability of ecosystems. When temperature swings quickly and widely from the norm, life forms in a lake can change dramatically and even disappear.
"These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening," said Catherine O'Reilly from Illinois State University in US.
"Combining the ground and satellite measurements provides the most comprehensive view of how lake temperatures are changing around the world," said Simon Hook from NASA.
The researchers said various climate factors are associated with the warming trend. 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.
The findings were published in the journal Geophysical Research Letters.
