Tahoe rapidly warming

INCLINE VILLAGE - Lake Tahoe's waters are heating up at twice the rate of the world's oceans, according to one of Lake Tahoe's leading scientists who addresed this and other local-level global-warming issues Wednesday at a lecture.

Bob Coats, a professor with the UC Davis Tahoe Environmental Research Center since 1971, talked about his studies on how warming will affect Lake Tahoe, its surrounding water resources and the basin's forest health.

Lake Tahoe's temperature has risen an average of .015 degrees Celsius per year since 1970, according to Coats, a figure placing the rate of warming at roughly twice the rate of the world's oceans.

"We feel very confident about the long- term trend," Coats said in a phone interview Monday. "When all the models are pointing in the right directions and are consistent with measured values, then you have to ask yourself, 'Is there something going on here?'"

A warmer lake may already be facilitating the spread of warm-water, non-native fish like large-mouth bass from sheltered marinas, and could also be detrimental to clarity of the lake.

"A warming lake is a more stable lake," said Coats. "Fine sediments would be mixed to greater depths less frequently."

This less-frequent mixing could leave sediment trapped near the surface where it would do the most damage to visibility.

During his lecture Wednesday, Coats also addressed predictions of a dwindling Sierra snowpack caused by a decrease in the number of days with temperatures below freezing and more precipitation falling as rain rather than snow.

Rain replacing snow "has already happened, and I'm pretty certain that it's going to continue happening," he said.

An increase in average nighttime temperatures will also take a toll on the snow that does reach the ground, according to Coats. Average nighttime temperatures in the basin have been steadily rising since 1914, going up approximately two degrees Celsius from 1914 to 2002.

This increase places the basin just above the 0.2 degrees Celsius per decade increase in global nighttime air temperatures seen by the National Oceanic and Atmospheric Administration.

If precipitation and warming trends remain in line with current trends over the next 100 years, Coats also expects a basin with vegetation similar to what is currently found around 3,700 feet.