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Are King Tides Becoming The ‘New Normal’ In San Francisco? Hardly


A recent post at The Mercury News, “With climate change, king tides could be the new normal,” asserts that climate change will make king tides more common and more impactful in the San Francisco Bay area due to sea level rise, which will supposedly rise two feet by 2050.

This is unlikely any time soon, and certainly not by 2050. [emphasis, links added]

The Mercury News describes recent king tides in the San Francisco Bay area, which were admittedly milder than expected, but writer Will McCarthy says still “they raised the specter of an increasingly tenuous relationship between water and infrastructure in the region.”

King tides are higher-than-normal tides that occur when the moon is closest to the Earth.

They can be exacerbated if they coincide with wind patterns pushing more water toward shore, increased rainfall, or other natural phenomena.

McCarthy admits that king tides are “natural regularly occurring phenomena as old as time” that are driven by lunar cycles, not climate change, but that “as climate change pushes sea levels higher, the flooding apparent during king tides could soon become permanent.”

McCarthy claims, without any source for his data, that “projections estimate that sea levels in the Bay Area could rise by approximately two feet by 2050, which would put our permanent shoreline at the water level seen during king tides.”

Data from the National Oceanic and Atmospheric Administration (NOAA) Tides and Currents database show that San Francisco sees a relative sea level trend of about 1.96 mm of rise per year. (See figure below)

Extending that to 2050, the rise is only 50.96 mm, almost exactly two inches, not two feet, as McCarthy claims.

There is a long-term record of sea level data starting in the 1850s for San Francisco, and there is no apparent acceleration in sea level trends that could spike the rate of rise to the point where two feet might be achieved by 2050. (See figure below)

A quick web search on king tides in San Francisco brings up the California Coastal Commission website, which may be where McCarthy got the two-feet-by-2050 figure.

This website links to a government report from 2018 that details the projected sea level rise for San Francisco and, lo and behold – the 1.9 feet by 2050 figure comes from a high-emissions modeling scenario that is based on RCP 8.5, which is a highly contentious worst-case scenario for climate modeling that climate scientists acknowledge is unrealistic, as Climate Realism details in posts here, here, and here, for example.

Worse still, even under the high-emissions scenario, the 1.9-foot-rise projection is given a 0.5% probability of occurring. The “likely” range lists 1.1 feet of sea level rise by 2050. [There are 25 mm in an inch]

Still, again, these projections are based on a modeling scenario that is well outside of realistic projections, and a study from 2014 that is out of date.

It’s shameful that the California government’s coverage of how climate change and sea level rise might impact their coastlines relies almost exclusively on RCP 8.5, as though it is a realistic “high emissions” scenario.

This isn’t new, however, as Climate Realism has seen in other coverage regarding California’s coasts (here and here for example), the high projections get a lot of press.

What is more shameful, however, is the lack of any curiosity or skepticism from the journalist class in California regarding these extreme claims.

A glance at San Francisco’s sea level rise data would call into question some of the state government’s claims, but practically no mainstream journalists are willing to do so.

Top photo by Alex Perry on Unsplash

Read more at Climate Realism

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