Report: Sea level rise poses grave threats
A new scientific model provides more certainty about how much ocean levels could rise in California in the next 30 years and predicts slightly less rising in some scenarios than previously thought. But the predictions still show grave threats to California, where 70% of the population lives near the coast.
Statewide, sea levels are due to rise by an average of 0.8 feet (9.6 inches) by 2050 compared to a baseline of 2000, according to the draft report. That is for what is considered “intermediate” level sea level rise, based on what is known now about likely levels of global warming in that period. Predictions become more difficult through the end of the century, when they are expected to rise by 3.1 feet at intermediate levels and up to 6.6 feet in a worst case. By 2150, they could go up by 6.1 feet or as high as 11.9 feet, though the authors say it’s difficult to have much certainty after 2100.
Released Friday by the California Ocean Protection Council, the new draft “State of California Sea Level Rise Guidance” is meant to help community planners and incorporates advances in science since the state’s last such report in 2018. The draft report was created in collaboration with a panel of scientists, mostly from California universities, and is based partly on new federal guidelines released in 2022. It is open to public comments until March 4, and a final version will be published likely in June.
“We have greater certainty and we’ve narrowed the range through 2050,” said Kaitlyn Kalua, deputy director of the Ocean Protection Council. “The longer-ranging scenarios are where there’s higher uncertainty and higher potential risk, which is challenging for planning.”
The various possible sea level futures for California are broken down into five categories: low, intermediate low, intermediate, intermediate high and high, depending on expected rates of global warming.
Sea level rise is due to vary within the state because of different influences such as tectonic activity, which gives the Humboldt Bay region the fastest rate of sea level rise in the state, predicted to reach 1.2 feet by 2050 at intermediate levels in the new report.
In San Francisco, the intermediate rate of sea level rise is predicted to be 0.8 feet, like the statewide average, and 0.6 feet in Alameda, the new predictions say.
In the last report, a “high” statewide sea level rise in 2050 was projected at 1.9 feet while the new draft report predicts 1.2 feet in the high scenario.
“It can be a reflection of a little bit of a slower acceleration than we thought,” said Laura Engeman, coastal resilience specialist at UC San Diego’s Scripps Institution of Oceanography and a co-chair of the science task force that contributed to the draft report. “There’s just more information about where we are in our climactic cycles. Sea level rise is not a linear process.”
But the slight change is not cause to celebrate. Even at around 1 foot of sea level rise by 2050, the potential and frequency for flooding will be much higher and would occur throughout the year, said Engeman.
“As sea levels increase, what is today’s king tide will be every month’s high tide,” said Engeman. Waves that would normally reach 10-15 feet become 11-16 feet with an extra foot of sea level rise, she added.
“For much of the Bay Area, anything over a foot of sea level rise is a major challenge,” said Warner Chabot, executive director of the nonprofit San Francisco Estuary Institute. “Sea level rise is the Bay Area’s No. 1 climate change threat, especially to underserved, disadvantaged communities. This state report clearly validates that threat.”
Chabot noted that the state’s most recent budget proposal included almost $3 billion in cuts to climate resilience, including $184 million in coastal resilience programs.
The new report also went into detail about how groundwater levels will rise along with sea levels, which can spread contaminants in the soil and threaten underground infrastructure. It could also make levees that are being planned to hold back flooding ineffective, said Kristina Hill, an associate professor at UC Berkeley and director at its Institute of Urban and Regional Development.
“Those conventional adaptation strategies to prevent flooding aren’t going to work,” said Hill, who was on the science task force advising the report. “Those levies will keep the waves out, but they won’t stop the groundwater from rising.”
The most recent science around climate change gives communities more granular knowledge about how to plan for the future, said Engeman.
“Between now and 2050 is a critical time for planning,” she said.
And, she said, there’s still a chance to stave off the worst predictions.
“The hope is that as a global society we mitigate our global warming temperature increases,” she said. “If we did that, the high sea level rise scenarios would likely get dropped.”