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UC Researcher Warns Campaign To 'Make Tahoe Blue' Again May Be Too Late

LAKE TAHOE (CBS SF) -- Lake Tahoe's famous crystal clear water is turning murky.

President Obama and concerned local leaders will gather at a summit Wednesday to discuss how to ''Keep Tahoe Blue.'

University of California at Davis researcher Brant Allan has been studying the lake for the last twenty years. He says the impacts of Tahoe's health extend far beyond the Tahoe basin. They are global.

Despite local efforts to clean up the lake, no bumper sticker campaign can curb climate change.

"If you look at the overall picture of the research for the last 15 years, it shows that climate change is having a greater and greater impact on the lake compared to human impact," says Allan. "They are starting to become equal."

The most recently released numbers show big changes.

Despite a normal winter, lake temperatures are rising at an unprecedented rate, and the surface temperature is at a record high.

The water isn't mixing as deeply and it lost almost five feet of clarity this year.

Tahoe's lake clarity is measured by dropping a 10-inch wide Secchi disk -- a circular, white disk resembling a dinner plate -- into the water and waiting to see when it disappears. Davis researchers reported in 2015 the average annual clarity levels at 73.1 feet. In the 60s it was almost 100 feet.

The lake hasn't been this murky since the 90s, before the campaign to keep the water blue began. The shift from human impact to climate change will also shift the focus of Wednesday's Lake Tahoe Summit, likely raising concerns and a lot of questions.

"With climate change we are looking at changes we haven't experienced before. We've always been focused on what the human impacts in the Tahoe Basin are. Now we've got to deal with what are the climatic impacts and the long-term effects of those," says Allan.

Despite decades of work and millions of dollars in improvements, keeping Tahoe blue could soon be out of human hands.

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