As we speak, President Obama is arriving in South Lake Tahoe preparing to deliver the keynote address at this year's Lake Tahoe Summit, an annual gathering since 1997 of federal, state, and local leaders "dedicated to the goal of restoring and sustaining Lake Tahoe as one of our most precious environmental treasures." The President is expected to speak to the topic of climate change, and as CBS 5 reports, it's climate change that is now becoming more to blame for the lack of clarity in North America's largest alpine lake, about which there has been an environmental protection campaign since the 1960's to "Keep Tahoe Blue."*

You've likely seen the bumper stickers, but according to UC Davis researcher Brant Allan, who's been studying the lake for the last 20 years, the situation may no longer be fixable through the reduction of human impacts on the lake.

"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," Allan tells CBS 5. "They are starting to become equal."

Allan notes that the lake is returning to levels of murkiness not seen since the 1990's, saying that when the last test was done in 2015 — involving dropping what looks like a 10-inch white plate into the water and recording the level at which it disappears — clarity stopped at 73.1 feet. To compare, back in the 1960's, it was 100 feet.

So, yes. Depressing!

In slightly better, earlier news, the Bay Area is uniquely well positioned to weather a rise in average temperature and sea level due to climate change in the next century, so there's that.

*This post has been corrected to show that the Keep Tahoe Blue campaign dates to the 1960's, not the 1990's.

Previously: Video: Rare Sighting Of Momma Bear And Cubs Swimming With People In Lake Tahoe