"That's a lot of water," he notes. "We're not saying that it's going to keep increasing at that rate, but the fact that it can change so quickly is disturbing."

'The fact that it can change so quickly is disturbing.' Geoffrey Schladow, UC Davis freshwater scientist

Even more disturbing to scientists is how all this warming has affected the lake's ability to mix its own waters, a natural process that is thermally driven. The warm winters have stunted that process, meaning that oxygen-rich surface water is not making it to the lake bottom, depriving fish and other life forms of oxygen. Scientists routinely measure how deep the mixing occurs -- the deeper, the healthier for the lake -- and last year's level was 262 feet, the most shallow ever recorded. Tahoe's maximum depth is more than 1600 feet.

"What we’re seeing now is that the climate and the weather are starting to affect the lake more directly," says Schladow, who notes that Tahoe is only a mirror held up to the rest of the state; if this critical mixing process is shutting down in Tahoe, it's doubtless happening in other lakes around the West.

For years, scientists have warned that the Sierra would gradually see more rain and less snow because of the warming climate, a trend that has potentially dire consequences for California's water supply. But the trend of the last few years has been stunning. The report's authors noted that during the winter of 2014-2015, just 6.5 percent of precipitation at the lake level fell in the form of snow. Decades ago it was more like a 50-50 mix.