Science News - Globally, Inland Lakes' Nighttime Temperatures Rising 1C/Decade Since Mid-1980s

[hatrack]

Throughout the past quarter-century, inland lakes have been experiencing a small, steadily rising nighttime fever. Globally, the average increase has hovered around 0.045 degrees Celsius per year, but in some regions the increase has been more than twice that — or about 1 °C per decade. In some regions — notably the Northern Hemisphere’s mid and upper latitudes — lakes have been warming faster than have surrounding air temperatures.

No question, the upticks have been small. They also appear to have been inexorable since at least 1985. Indeed, these observations, published November 24 in Geophysical Research Letters, represent “a new independent data source for assessing the impact of climate change throughout the world,” according to the study’s authors, NASA scientists Philipp Schneider and Simon Hook of the Jet Propulsion Laboratory at Caltech.

JPL’s thermal survey of 167 major lakes relied on satellites. Like hovering thermometers, those eyes in the sky have been collecting infrared — heat — measurements of surface features. Nighttime lake surfaces were surveyed during summer months in the Northern Hemisphere and in January through March in the Southern Hemisphere. Overall, lakes in northern Europe appeared to be warming fastest. In North America, lakes in the U.S. Southwest warmed somewhat faster than did the Great Lakes.

An unrelated study due out soon in the same journal has mapped changes in the existence and size of 2,938 lakes throughout China. The new analysis compared data collected between the 1960s and ’80s with others from the mid-2000s. And it finds not only a 13 percent reduction in China’s overall surface area covered by lakes but also a vanishing of almost 250 discrete water bodies. Those lake losses do not just reflect the drying up of some little ponds, the authors note, because their analysis surveyed only lakes that initially had been at least 1 square kilometer in size.

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http://www.sciencenews.org/view/generic/id/66448/title/Science_%2B_the_Public__Lakes_are_warming_across_the_globe

[OKIsItJustMe]

1. Earth's lakes warming due to climate change

http://www.agu.org/news/press/pr_archives/2010/2010-40.shtml

Earth's lakes warming due to climate change

AGU Release No. 10–40
23 November 2010
For Immediate Release

WASHINGTON—In the first comprehensive global survey of temperature trends in major lakes, researchers have determined that Earth's largest lakes have warmed during the past 25 years in response to climate change.

Philipp Schneider and Simon Hook of NASA's Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperatures of 167 large lakes worldwide.

They reported an average warming rate of 0.45 degrees Celsius (0.81 degrees Fahrenheit) per decade, with some lakes warming as much as 1 degree Celsius (1.8 degrees Fahrenheit) per decade. The warming trend was global, and the greatest increases were in the mid- to high-latitudes of the Northern Hemisphere.

"Our analysis provides a new, independent data source for assessing the impact of climate change over land around the world," said Schneider, lead author of the study that will be published on 24 November in the journal Geophysical Research Letters, a publication of the American Geophysical Union. "The results have implications for lake ecosystems, which can be adversely affected by even small water temperature changes."

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http://dx.doi.org/10.1029/2010GL045059