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Environment & Science

#ISeeChange: Could San Francisco's famous fog disappear?




A view of the north tower of the Golden Gate Bridge.
A view of the north tower of the Golden Gate Bridge.
Justin Sullivan/Getty Images

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Grace Gornall grew up in the Bay Area. As a child, she remembers days that were cool, crisp, and foggy. “San Francisco as far as I’ve known, and I grew up here, has always been in the mid 50s, upper 60s at the most,” Gornall said.

She lived in Los Angeles for five years as an adult, and when she moved back to San Francisco, the city’s climate felt warmer and muggier. There  also seemed to be a lot less fog. "I would compare it, personally, to more of the days that I was in Hollywood," she added.

This made her wonder, "are we looking towards San Francisco’s climate essentially becoming closer to Southern California’s climate?"

Travis O’Brien says yes, in some ways, we are. O’Brien is a research scientist at the Lawrence Berkeley National Lab at UC Berkeley. He studies things like fog and explains that, in the San Francisco area, the wind blows off the ocean and stirs up the water, and then some of that moisture blows onto land and creates that heavy mist

"You get the fog droplets on your skin, they evaporate off and it’s a very distinct cold,"  says O'Brien. "Whereas, when it’s muggy out, there’s not cloud droplets in the air, they’re not getting on your skin and re-evaporating away and sucking heat away from you."

The temperature in coastal cities is directly related to the temperature of the ocean, he explains. In the case of San Francisco, it’s about 55 degrees Fahrenheit, basically the same as what Gornall remembers as a kid.

But, O’Brien notes, the Pacific Ocean is getting warmer. And as the ocean warms up, the moisture in the fog warms up too and it evaporates. Research shows that fog in Northern California has decreased over the last hundred years by about a third. O’Brien says, if that continues, "We could expect to see a roughly fog-free San Francisco by the end of this century." 

That could mean the end of those postcard-perfect images of the Golden Gate Bridge hidden in the mist. And while mornings in Berkeley could get a little sunnier, the effects could go beyond the Bay Area.

“There’s definitely a ‘it could be nicer weather in my backyard because of climate change,’ sort of side to this,’” O’Brien said, “but the other part of our backyard up here is the redwood forests.” He says less moisture in the air could be a big problem for California’s coastal Redwoods. “Something like a third of their water comes from fog water. And that comes during the driest time of year. It’s not clear whether they’ll be able to survive that.”

No one knows for sure if the fog will disappear from San Francisco, or what will happen to the redwoods. There are many variables. But if the ocean and the air continues to warm, O’Brien says it could be a dramatically different looking Bay Area.

A Bay Area where, as Gornall noticed, San Francisco’s weather is a lot more like Hollywood’s. "The temperature in general, it was lighter, you could wear a t-shirt, without a jacket," Gornall said. "Personally I love it, but I know that that’s not a good thing."

#ISeeChange is a national effort to track how climate change is affecting our daily lives. 

Notice any bugs in your backyard lately? Wondering why you're seeing coyotes where you don't expect? Seen changes in your favorite tide pool? Snap a picture and tag it @KPCC and #ISeeChange on Twitter or Instagram, let us know through our Public Insight Network, or post your questions on www.iSeeChange.org. Then see what others have found and observed in their environment.