Producer's Notes: Science of Fog

While foggy days aren’t ideal for a summertime picnics, coastal fog does benefit the ecology of the Bay Area.

Normally I wouldn’t be hoping for a chilly, foggy day during the summertime here in San Francisco. For the purposes of filming our Science on the SPOT story, “Science of Fog,” however, we hoped that the Presidio would be socked in with a thick blanket of fog for our interview with UC Berkeley’s Todd Dawson.

Luckily, Mother Nature cooperated with us to give us plenty of atmospheric fog to work with for our shoot. We interviewed Dawson about the two types of fog that are prevalent in the Bay Area, and about his ongoing research on the decline of fog along the California coast.

Dawson also elaborated on some conflicting reports in the media on whether fog was declining or actually increasing. “There was a study done previous to ours over a shorter period of time. It’s only about 35 years. And the records came only from the Los Angeles area and from San Francisco. They weren’t a comprehensive sort of investigation of all of the temperature records that we’ve done throughout California.

Those investigators came to the conclusion based on a model that they had developed based on those just temperature records, [with] no fog data. They ran the model, and it gave them an output that says, ‘Oh, fog is going to be increasing.’

Our investigation is much longer. It takes place over more than 110 years. It’s hourly temperature records and precipitation records. It involves all of the fog data from the airports that we’ve been able to get throughout the entire state. And, of course, it’s a longer period.

And just like the stock market, if you look at a small part of a change in the stock market, on any given day it might look like it’s rising. But if you look over 100 years of the stock market, you’re going to say that, ‘Ah, stocks have been declining steadily over that longer period of time.’

So what looks to be a bit of a conflict is really just because we’re looking at different windows of time and different kinds of information. And I think that’s why sometimes people kind of go, “Well, somebody told me that fog’s supposed to be increasing.’ And our data is saying no, it’s decreasing. It kind of depends on the window of time you’re looking at.”

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