From afar, San Francisco looks lofty compared to the sea that surrounds it on three sides. But take a walk down the Embarcadero on the right day, and you can find yourself up to your ankles in brackish Bay water. Scientists have a word for these super high tides, but it's not nearly as catchy as what the activists call them: king tides.
King tides---a type of perigean spring tide (there's your science jargon)---occur when extra-high tides line up with some other meteorological anomalies. They're not a huge deal: The water flowing over the seawall is part novelty, part nuisance. But these rare days hint at a new normal, when sea level rise will render current coastlines obsolete.
Tides happen because the sun and moon yank on the spinning Earth's oceans. During new and full moons, the sun and moon line up, and their gravitational pulls join forces, tugging on the ocean. These are called spring tides. But wait, there's more. Every year at the beginning of January the Earth's not-exactly-circular orbit takes it screaming by the sun's surface---a mere 91.4 million miles away! Relax, that's not close enough to do much but contribute a little extra gravitational yanking to the oceans, turning spring tides into king tides.
On January 21 and 22, the king tide will bring San Francisco's shoreline about a foot higher than average high tide. "El Niño brings another six to 16 inches to the equation," says David Behar, climate program director for the San Francisco Public Utilities Commission. And should the state get hit with one of its signature offshore winter squalls, add another another three and a half feet. Stacked atop one another, these astronomical, oceanographic, meteorological phenomena provide a real life watermark for the three to six and a half feet (depending on who you ask) of sea level rise scientists expect by 2100.
The glimpse into the future is fleeting. Peak king tide only lasts for about a minute before slowly receding. A storm surge, if it comes, lasts hours, days maybe. El Niño will be gone in several months. "Sea level rise is distinct in that it is permanent, for all intents and purposes," says Behar.
Without some kind of adaptation, that sea level rise is going to wreck a lot of the Bay Area coastline. One extra foot drowns roads in Marin County. Two feet and you lose runways at Oakland's and San Francisco's international airports. Six feet and the Googleplex is a fortified island in an industrial lagoon. Thousands of homes, businesses, and pieces of infrastructure will be threatened.
Threatened enough that the nine counties surrounding the Bay are contemplating a $12 tax on every parcel of real estate, with the money going towards climate adaptations. "The money would primarily go towards wetland restoration, but the tax is explicit in saying these measures are to address sea level rise," says Behar.
And the Bay Area isn't the only region facing these kinds of threats. Four out of every 10 Americans live in FEMA-designated Coastal Shoreline Counties, where encroaching waters can cause serious damage. The seas are rising gradually, but their first forays onshore will be during events like king tides and storms. Eventually, the novelty is going to wear off.
