Report: Rising seas threaten Sonoma County as climate warms

by Guy Kovner, The Press Democrat

Global warming likely will drive the sea level in Sonoma County up as much as 3 feet and potentially more than twice that high by 2100, according to a state-commissioned report released last week.

The report, authored by a team of seven scientists from California to Massachusetts, also said in the most extreme scenario — rapid melting of the Antarctic ice sheet — the sea level rise throughout the Bay Area, including Sonoma County, could run as high as 10 feet.

That rate of sea level rise would be 30 to 40 times faster than the pace over the past century, the 71-page report said.

Consequences are already evident, local officials said, with winter storms and exceptionally high tides causing flooding on Highway 37 along the edge of San Pablo Bay and in Duncans Mills on the Russian River, closing Highway 101 ramps in Marin County and splashing water onto San Francisco’s Embarcadero.

King tides, caused by the relative positions of the Earth, sun and moon, mimic sea level rise, backing up the Petaluma River “all the way to Dempsey’s Restaurant” in downtown Petaluma, said Sandy Potter, a Sonoma County planning manager.

The tides also back up the Russian River, causing flooding at Duncans Mills, about 4 miles from the ocean, she said.

Low-lying San Francisco International Airport is also vulnerable, and on a global scale 150 million people live within 3 feet of high tide, said Gary Griggs, chairman of the science team and a professor of Earth sciences at UC Santa Cruz.

The report, “Rising Seas in California,” was requested by the California Ocean Protection Council and the California Natural Resources Agency in collaboration with the governor’s office as a guide for state and local decisions concerning California shorelines.

Rising seas threaten “hundreds of miles of roads and railways, harbors and airports, power plants and wastewater treatment facilities, in addition to thousands of businesses and homes,” the report said.

Sea level rise is inevitable: It’s been measured by satellites at an average rate of 1.3 inches per decade since 1993, more than twice the rate over the entire 20th century, according to the report.

The campaign to curb fossil fuel combustion can make a difference, Griggs said.

Under a “business as usual” scenario, with no significant global effort to curb greenhouse gas emissions from burning coal, oil and gas, there’s a 67 percent probability the sea will rise up to 3.4 feet in Sonoma County by 2100 and a one-in-200 chance it would rise 6.9 feet, the report said.

A strong global campaign, cutting carbon dioxide emissions to zero by 2080, would blunt the ocean’s rise by about 1 foot, down to a high probability of 2.4 feet and long odds of 5.7 feet in the county by 2100, according to the report.

For people living close to the water, “that 1 foot is really important,” Griggs said in an interview.

County officials have anticipated a 6-foot rise, which would result in flooding at Bodega Bay, Duncans Mills, Jenner and other areas. Suki Waters, owner of WaterTreks EcoTours, a kayak and stand-up paddle board rental business in Jenner, said that likely would mean flooding of Highway 1 at high tide.

“I’m definitely a sustainability advocate,” said Waters, a Kashia Pomo whose ancestors inhabited Penny Island in the Russian River estuary at Jenner. “We need to do everything we can to offset that carbon.”

But President Donald Trump is reversing key climate change policies, Griggs said.

“I think that’s been evident from day one,” Griggs said, citing Trump’s move to revive the nation’s flagging coal industry.

Trump administration officials will reportedly meet this week to discuss whether the president should stick to his campaign promise to pull out of the Paris climate agreement in which nearly 200 nations committed to limiting their carbon dioxide emissions.

“Policy makes a difference,” Griggs said. “To hold sea level rise to any reasonable value, we’ve got to make serious changes in how we produce energy.”

If the United States pulls out of the nonbinding Paris accord, other major nations — China, India, Japan and European countries — may slacken their efforts, as well, he said.

“Effects of many decisions made today will persist for decades,” the report said, for some “50, 70 and even 100 years into the future.”

It comes as scientists are paying more attention to the role of the Greenland and Antarctic ice sheets as key drivers of rising seas.

All of the world’s mountain glaciers contain only enough ice to raise sea levels about 1.5 feet, the report said. If the entire Greenland ice pack melted, it would raise seas 24 feet while melting of the Antarctic ice would push the oceans up a whopping 187 feet.

No such meltdown is likely, even over thousands of years, the report said, but a fractional loss of Greenland or Antarctic ice could have “devastating consequences” for global shorelines.

California would be especially impacted, as a loss of West Antarctic ice that caused a global sea level rise of 1 foot would result in a 1.25-foot rise here, the report said.

It includes an “extreme scenario” that anticipates a 10-foot sea level rise in the Bay Area by 2100, which should not be overlooked, said Sam Veloz, climate adaptation group director for Point Blue Conservation Science, a Petaluma-based nonprofit research organization.

“I would want to be prepared for the higher end” of the forecasts, he said.

Flooding around the Bay Area during storms this year is “just going to get worse,” as sea levels rise, Veloz said, calling for attention to the problem.

“We do have some time,” he said, referring to the sea level estimates stretching to 2100. “The danger is we do have some time.”

The report, which will be presented at an April 26 meeting of the Ocean Protection Council in Sacramento, is available online at


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