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

Craig Miller

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.

Looy is looking for pollen in the cores, to learn what plants grew around Clear Lake when the climate was warmer, and how the plant life changed as the climate did. Then she’ll compare that data to models other scientists have made that attempt to paint a picture of California’s future landscape.

To extract the cores, Looy and her team are working on a barge that looks — and sounds — like a construction site that sprouted in the middle of the lake. In fact, they rented the barge from a local construction company. DOSECC, a company that specializes in scientific drilling (the name stands for Drilling, Observation and Sampling of the Earth’s Continental Crust), supplied the drill and the drillers — the drill they’re using would normally be used for mining for precious metals.

Looy acknowledges that her previous ecology fieldwork didn’t quite look like this. “Normally we go into a forest and we say ‘OK, I’m going to measure all the plants, for instance, in a 100 x 100 meter area,’ but this is completely different,” she shouts, over the incessant racket on the barge. “It’s a different type of work.”

As DOSECC’s drillers pull the cores up from the lake bed, they hand them off to UC Berkeley grad students, who work with scientists from LacCore, a group that works exclusively on lake cores. The students cut the ten-foot cores into more manageable segments, then seal and label them.

The cores will eventually go to LacCore’s facilities at the University of Minnesota, where half of each one will be stored permanently, in a library of lake bed cores from all over the world. Looy will slice up and analyze the other half, counting and identifying miniscule pollen grains, documenting what it looked like around Clear Lake through the ages. And that will help us imagine what the landscape around Clear Lake will look like in the future.

Looy’s Clear Lake coring project is part of the Berkeley Initiative in Global Change Biology, a program focused on cutting edge, cross-disciplinary climate change research.

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.”

The study also forecasts several climate change impacts on Lake Tahoe itself. Prolonged droughts in California could cause the lake level to fall below out-take valves, which feed the Truckee River. The Truckee supplies water to Pyramid Lake and the city of Reno, Nevada. Output levels have fallen in the past, but under the worst case climate change scenario, those periods could stretch 10 to 20 years.

That would also change the face of the iconic lake. “Suddenly lakefront homes would be hundreds and hundreds of feet from the water. It’s going to be a very different looking lake,” said Schladow.

Lake Tahoe’s unique ecology could also change. Mixing of water from different depths is a critical process for any lake, since it takes oxygen from the surface and makes it available for fish and other species living throughout the water column. Because Lake Tahoe is so deep, today it only mixes fully every three to four years. By the second half of the century, that mixing period will become longer. “At some point, it may not mix for decades at a time,” said Schladow.

Schladow says the study focused on Lake Tahoe as an important case study for changes happening throughout the Sierra Nevada. “These same processes are happening everywhere across the West. Tahoe is the canary in the coal mine.”

Forecasting climate change impacts like these at the regional level has become a Holy Grail for climate scientists. Historically, computer climate models could only scale down to sections of land hundreds of miles across, which made it difficult to predict changes in a landscape as varied as California.

Schladow says newer climate models allow them to see changes at a much more granular level. “What we were able to do is to use grids that were more like one or two miles. That way we could distinguish between effects at the mountain peaks and effects down at the lake level.”

Schladow is hopeful that this study can give land and water managers an early indication of what the future may hold.