New Clues to California’s Climate Future From the State’s Oldest Lake

Scientists are using ancient pollen to help predict what’s next for California’s flora

A radio version of this story aired on The California Report.

Clear Lake, north of San Francisco Bay, is California's oldest lake and a potential treasure trove for climate scientists.

Clear Lake is one of the largest lakes in the state, and one of the oldest in North America. For half a million years or more, pollen and dead bugs have been collecting on the bottom. That gives scientists a unique opportunity to look deep into California’s past to learn what’s grown here through ice ages and warmer “interglacial” periods.

Dr. Cindy Looy, an assistant professor in Berkeley’s Department of Integrative Biology, is leading a project to core Clear Lake, unearthing sediment that’s been collecting on the lake bed for up to 200,000 years. Looy is especially interested in the interglacials, times between ice ages, when the climate was warmer. We’re in one now — it began about 12,000 years ago — but Looy is prospecting in the one that began about 130,000 years ago, when the earth might have been warmer than it is now.

“There are a lot of people working on models to predict what the climate will look like,” she says. “In order to find out how plant life and animal life will respond to climate change, you can go back in the past, to periods where the climate was changing rapidly and even getting warmer than it is today.”

Video produced by Harry Gregory.
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Tahoe Forecast: Shrinking Snow, Longer Walk to the Water

Lake Tahoe's water level could drop within the century. (Photo: Lauren Sommer)

The average snowpack in the Tahoe Basin could decline 40 to 60% by 2100 and some years could see all rain and no snow. That’s according to climate change forecasts released this week by the UC Davis Tahoe Environmental Research Center.

The decrease in snowpack would be driven by two processes, according to study author Geoffrey Schladow. With warmer temperatures, more precipitation will fall as rain during the winter, instead of snow. And as any skier knows, when rain falls on snow, it melts the snowpack in what scientists call “rain-on-snow” events.

These findings are a concern since the Sierra Nevada snowpack is often called California’s “frozen reservoir.”  That reservoir is critical to the state’s water supply — and it’s free. “What the snowpack affords us is a way to very economically store water,” said Schladow. “If the water is falling as rain, rather than snow, then we have to build more dams and reservoirs to catch it, which is expensive.” Continue reading