World's lakes getting hotter, more than the air

Seth Borenstein, Associated Press Yahoo News 23 Nov 10;

WASHINGTON – A first-of-its-kind NASA study is finding nice cool lakes are heating up — even faster than air.

Two NASA scientists used satellite data to look at 104 large inland lakes around the world and found that on average they have warmed 2 degrees (1.1 degree Celsius) since 1985. That's about two-and-a-half times the increase in global temperatures in the same time period.

Russia's Lake Ladoga and America's Lake Tahoe are warming significantly and the most, said study co-author Simon Hook, a scientist at the Jet Propulsion Lab in Pasadena, Calif. Tahoe has heated up by 3 degrees (1.7 degrees Celsius) since 1985, while Ladoga has been even hotter, going up by 4 degrees (2.2 degrees Celsius).

The study was published Wednesday in the journal Geophysical Research Letters.

Hook and his colleague used several satellites and looked at thermal infrared images of the lakes in winter and summer. They also confirmed the numbers by comparing them to buoy data.

"It fits with what we see with air temperature measurements," Hook said. "We were surprised that in some places the lakes appear to be warming more than the air temperature."

The next question to look at is why the lakes seem to be warming faster than the air or land, Hook said. One reason could be the way lakes warm — in a more gradual manner than land but also slower to cool.

NASA climate scientist Gavin Schmidt, who was not part of the study, said the research made sense and adds another independent measuring system to show that the world is warming up. Eleven different indicators — including air temperature, humidity, snow cover, ocean heat content — show statistically significant man-made global warming, while no environmental measurements show otherwise, according to the National Oceanic and Atmospheric Administration.

Warming lakes is No. 12 and "another brick in the wall," said University of Victoria climate scientist Andrew Weaver.

Overall, 41 lakes increased temperatures in a statistically significant way, with another 59 individually warming but not enough to be considered significant. Only four showed temperature drops, but not significantly, Hook said.

NASA says Earth's lakes are warming
Yahoo News 23 Nov 10;

WASHINGTON (AFP) – The Earth's largest lakes have warmed up over the past 25 years in response to climate change, the US space agency said Tuesday, announcing the first such global study of its kind.

Scientists Philipp Schneider and Simon Hook of NASA's Jet Propulsion Laboratory in Pasadena, California used satellite data to measure the surface temperature of 167 lakes around the world, NASA said.

"They reported an average warming rate of 0.81 degrees Fahrenheit per decade, with some lakes warming as much as 1.8 degrees Fahrenheit per decade," NASA said in a statement.

"The results were consistent with the expected changes associated with global warming," it said.

Researchers found the "largest and most consistent area of warming was northern Europe," while the "warming trend was slightly weaker in southeastern Europe, around the Black and Caspian seas and Kazakhstan," NASA said.

"The trends increased slightly farther east in Siberia, Mongolia and northern China."

The southwestern United States experienced "slightly higher" trends than the Great Lakes region, while the tropics and mid-latitudes of the Southern Hemisphere showed "weaker" warming, NASA said.

"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 published this week in the journal Geophysical Research Letters.

"The results have implications for lake ecosystems, which can be adversely affected by even small water temperature changes."

NASA selected bodies of water that were at least 193 square miles (500 square kilometers) or larger, and had significant amounts of water away from the shoreline so that land temperature changes did not interfere with measurements.