Lake Tahoe is pretty. The water is clear; the mountains surrounding it are beautiful. For half a century, the environmental group Keep Tahoe Blue has fought to preserve the region’s environmental sanctity, primarily by putting bumper stickers on Volvos, as far as I can tell.

Turns out that those Volvos are doing more harm than good. From the Santa Cruz Sentinel:

Climate change could profoundly affect the Tahoe area, scientists say, taking the snow out of the mountains and the blue out of the water. …

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New climate models show that in a worst-case scenario average temperatures in the Tahoe area could rise as much as 9 degrees Fahrenheit by the end of the century. That’s equivalent to moving Lake Tahoe from its current elevation of 6,200 feet above sea level to 3,700 feet, climate scientists report in a special January issue of the journal Climatic Change. That’s as high as the peak of Contra Costa County’s Mount Diablo, which gets only an inch of snow a year. …

It’s not just the mountains that would look different in a warmer climate, according to Climatic Change. The worst-case scenarios also predict a devastating ecological collapse of the lake and loss of its signature clarity and blue color.

Many lakes undergo a process every year, or every few years, that keeps the lake water well-mixed. As water temperature changes through the seasons, it creates circulation in the lake. The warm water on top of the lake in summer cools off in the fall and sinks, mixing with cold deep water. In a warmer climate, the surface water won’t cool off enough to mix with deeper water.

Without that mixture, oxygen doesn’t penetrate the lake, changing its chemistry. So long clarity. So long blue.

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Sadly, there’s not a lot that can be done besides stemming climate change globally. The process is already underway; last season, Tahoe ski resorts didn’t see natural snow until January. Happily, this season started off better.

As we’ve noted before, the problem isn’t confined to Tahoe. Warming temperatures are threatening mountain climates across the country. But few have environmental legacies — and environmental success stories — as rich as Lake Tahoe’s.

A recommendation, then, for those who wish to help: Get a “Keep Tahoe Blue” bumper sticker and paste it over your car’s tailpipe.

A wintry scene from the mountains near Tahoe. Enjoy it while you can.

A wintry scene from the mountains near Tahoe. Enjoy it while you can.