Everyone’s talking about this new 5,000-word New York Times love letter and research piece about the San Francisco fog, but it describes our fair fog’s cloudy future, as evidence indicates the fog has decreased by a third over the last 50 years or so.

Through much of the Labor Day week and weekend heat wave Northern California endured this year, the running joke was that the entire Bay Area and beyond was boiling with temperatures 100 degrees and above — but here was San Francisco, chillin’ in the mid-70s. And while the simple explanation for this was “Because of the fog,” science lacks a deeper explanation of how fog worlds and why; fog is a niche field whose effects are only regularly felt in a few certain areas, and the fog itself is transient and difficult to track.

Today’s New York Times has a 5,000-word, longform research piece on the fog in San Francisco that’s been an instant, huge hit on Left Coast social media since it was published. It trots out our Twitter personalities who impersonate the fog, our quirky commercial products that try to monetize the fog, and some recognizable SF names describing highly recognizable fog phenomena.    

“There’s rarely a July Fourth fireworks celebration that anybody actually sees,” SF Rec and Parks general manager Phil Ginsburg is quoted as saying in the piece, for the benefit of anyone who's never spent a July here.

But the underlying premise of the article is a lot less fun. Citing a research piece by a UC Berkeley team in the Proceedings if the National Academy of Sciences, they note that “Using observational data at airports in the coastal redwood region — from central California to its northern border, including the Bay Area — they found that the frequency of fog, measured by fog hours per day, had dropped 33 percent since the middle of the 20th century."

“Fog has decreased, more or less everywhere,” agrees University of Münster professor of climatology Otto Klemm later in the article, noting the climate change phenomenon of less fog has been observed worldwide. “Of about 1,000 stations, 600 or 700 show a statistically significant decrease. All over Europe, all over North America, South America — everywhere.”

There is coastal fog in several other countries in the world (Chile, Morocco, Peru) and like here in the U.S., foggy areas often happen to be on the western coast. Scientists have tried the idea of catching that fog and turning it into water on so-called “fog farms” in these places to address water shortages. (We’ve tried this in San Francisco, too.)

“I would tend to think of it as a small drop in the bucket,” said “fog catcher” and CSU Monterey Bay professor Dan Fernandez. “But we need a lot of small drops in the bucket to deal with what we have coming.”

Clues may lie in our famed, tall redwood trees, which have apparently figured how to harvest water from fog. They’re always moist with the ground soggy beneath them, and even in the dry season, sustaining moisture and allowing a whole ecosystem of other plants, insects, and small animals to survive because of the redwoods. The Times estimates that “30 to 40 percent of their annual moisture arrives in the form of fog.”

But decreases in fog are affecting not only the redwoods, but also the wine grapes of wine country, and everything that grows on the northern California coast. These alleged decreases in fog are bedeviling issue, though, because there is no agreed-upon gauge for measuring fog or its volumes.

“We know that the planet is warming, we know that oceans are getting warmer,” Indiana University assistant professor of earth and atmospheric sciences Travis O’Brien told the Times. “What we don’t know is what’s happening in the really near coastal environment. In particular, ocean temperatures right along the coasts are a big question mark, and they have long been thought to be really important for coastal fog.”

Or it could be, in true fog fashion, that the results are too murky to interpret because we know so little about the fog. The Times adds that “Other researchers, using satellite technology, concluded this month ‘that the number of foggy days fluctuates considerably year-to-year with no discernible positive or negative trend occurring between 2000 and 2020.’”

Related: Ask A San Francisco Native: Has The Fog Always Been Named Karl? [SFist

Image: Ziggy Stone via Unsplash