SAN FRANCISCO (KRON) – The morning fog will be chilling the morning air of San Francisco less and less over the next decades, as it is already disappearing, according to a UC Berkeley scientist and government records.
Last week, KRON4 reported on why the City By The Bay’s fog is named Karl in the first place. As it turns out, the fog is lifting. Summertime coastal fog declined 33% over the course of the 20th Century, according to the Pacific Coastal Fog Project of the United States Geological Survey.
Todd Dawson, an ecology professor at the University of California, Berkeley, told KRON4 that global warming is the culprit.
“The fog records only go back 70 years, but temperature records go back more than a century, and there’s a strong association in changes of temperature and changes in fog,” Dawson said. “I’m not sure the government would show [causation] explicitly, but … long-term records of temperature inland and on the coast show things are warming.”
Dawson said that the coast is warming “at a slightly warmer rate” than inland, which has dire implications for Karl. The familiar fog is formed when the heated air from the city rises, creating a low-pressure zone that sucks in cold, foggy air from above the Pacific. This is most common in the summer, which caused Mark Twain to (allegedly) say “The coldest winter I ever spent was a summer in San Francisco.” This is also why the fog is most prevalent on the westside, close to the ocean.
“A lower temperature difference means we lose the vacuum that pulls the fog ashore,” Dawson said.
Dawson said climate change is making it hard to model just how much the fog will decline over the next decades. El Nino/La Nina, the drought, and changes in ocean currents make the future obscure.
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“I do think the trend of the fog declining is going to continue but the how to forecast how that’ll play out is very challenging,” he said.