Climate change rapidly warming world’s lakes, threatening freshwater supplies

Temperature increases close to or above the average .61 degrees F rise were seen in some of the world’s most popular waters, including Lake Tahoe (+.97 F by hand, +1.28 by satellite), the Dead Sea (+1.13 F), two reservoirs serving New York City, Seattle’s Lake Washington (+.49 F), and the Great Lakes Huron (+1.53 F by hand, +.79 by satellite), Michigan (+.76 F by hand, +.36  by satellite), Ontario (+.59 F) and Superior (+2.09 F by hand measurement, +1.44 F by satellite).

See a table of lake temperatures here.

Study co-author Simon Hook, science division manager at NASA’s Jet Propulsion Laboratory in Pasadena, California, said satellite measurements provide a broad view of lake temperatures over the entire globe. But they only measure surface temperature, while hand measurements can detect temperature changes throughout a lake. Also, while satellite measurements go back thirty years, some lake measurements go back more than a century.

“Combining the ground and satellite measurements provides the most comprehensive view of how lake temperatures are changing around the world,” he said.

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.

Previous work by Hook using satellite data indicated that many lake temperatures were warming faster than air temperature and that the greatest warming was observed at high latitudes, as seen in other climate warming studies. This new research confirmed those observations, with average warming rates of 1.3 degrees Fahrenheit (0.72 degrees Celsius) per decade at high latitudes.

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, where fish is an important source of food.

“We want to be careful that we don’t dismiss some of these lower rates of change,” said Hampton. “In warmer lakes, those temperature changes can be really important. They can be just as important as a higher rate of change in a cooler lake.”

In general, the researchers write, “The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.”

WSU notes that the study exemplifies the interdisciplinary work of WSU’s Grand Challenges, areas of research addressing some of society’s most complex issues. The study is also in keeping with the theme of the challenge “Sustainable Resources: Food, Energy and Water,” which will develop strategies that link optimized agricultural practices, water management and energy production.

— Read more in Catherine M. O’Reilly et al., “Rapid and highly variable warming of lake surface waters around the globe,” Geophysical Research Letters, Early View (16 December 2015) (DOI: 10.1002/2015GL066235)