Lakes Warming Up, Say NASA

The temperatures of lakes throughout the world have risen during the past 25 years according to a newly published NASA study. 

NASA used satellite data to measure the surface temperatures of 167 lakes worldwide and found an average warming rate of .81 degrees Fahrenheit per decade and in some lakes, as much as 1.8 degrees Fahrenheit per decade.

The study's results incorporated other techniques to verify the satellite data, such as direct measurements of water temperature.

Simon Hook, a scientist with NASA's Jet Propulsion Laboratory in California said the greatest increases were in the mid- to high- latitudes of the Northern Hemisphere, in a pattern consistent with changes associated with global warming.

He added: "From a scientific point of view, small differences in lake temperatures can have big change in a lake's ecosystem – a new fish species that people don't want, new plants; so from our point of view, what we want to do next is understand what the impact of these changes is going to be on the lake's ecosystem."

Of the 167 lakes surveyed, researchers were able to use data from 104, with 41 producing results that were "statistically significant," he said. Four lakes showed signs of cooling, but the differences were small enough to render them neutral, Hook said.

The satellite temperature trends largely agreed with trends measured by buoys in the Great Lakes, Earth's largest group of freshwater lakes in terms of total surface area and volume.