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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.
The thermal survey of 167 major lakes by the Jet Propulsion Lab at CalTech relied on satellites collecting infrared 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. The report can be found at http://www.agu.org/pubs/crossref/2010/2010GL045059.shtml.
An unrelated study 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. It found a 13 percent reduction in China's overall surface area covered by lakes, and also a vanishing of almost 250 discrete water bodies. Those lake losses do not just reflect the drying up of some little ponds, the researchers note, because their analysis surveyed only lakes that initially had been at least 1 square kilometer in size.
Most lake disappearances occurred in northern provinces and autonomous regions. Although the evidence is "limited," the researchers note, in these areas lake reductions or losses "might be associated primarily with climate change." By contrast, lake losses or contraction in southern provinces appear most likely due to the effects of human influences, which presumably would reflect diversion for irrigation and drinking water or landscape remodeling for urban development. The report (in Chinese) can be found at http://www.hjcz.org/bbs/simple/index.php?t261265.html. It will be published in the near future in the Geophysical Research Letters [doi:10.1029/2010GL045514].