A slow-moving emergency is lapping at California’s shores — climate-driven sea-level rise that experts now predict could elevate the water in coastal areas up to 10 feet in just 70 years, gobbling up beachfront and overwhelming low-lying cities.

The speed with which polar ice is melting and glacier shelves are cracking off indicates to some scientists that once-unthinkable outer-range projections of sea rise may turn out to be too conservative. A knee-buckling new state-commissioned report warns that if nothing changes, California’s coastal waters will rise at a rate 30 to 40 times faster than in the last century.

The potential result: crippled economies, compromised public safety, submerged infrastructure and a forced retreat from our iconic Pacific coast.

No state has done more than California to curb greenhouse gas emissions that contribute to climate change and sea-level rise. But experts say that even if carbon reductions continue, residual warming of the ocean will continue unchecked, breeding surges that will impact the state’s coast and Sacramento-San Joaquin Delta.

Last month the U.S. Geological Survey estimated that without concerted intervention, as much as 67 percent of Southern California’s beaches could be lost to rising seas by the end of the century.

A consensus of scientific research makes catastrophic projections that, in the worst case, will be reality by the end of this century:

• International airports in San Francisco and Oakland will face flooding, rendering them unusable.
• Housing perched on fast-eroding coastal bluffs in Pacifica and elsewhere will continue to crash into the sea.
• Malibu’s Broad Beach will dwindle into a seldom-seen slice of sand, its name an oxymoron.
• Flooding in the Delta will overwhelm rivers and strain levees critical to California’s water supply.
• Power plants, nuclear waste sites and other sensitive waterside sites need to be fortified or will be lost.
• Roads, bridges and railways along the coast from Mendocino to San Diego will be abandoned and relocated inland.
• San Francisco’s Embarcadero and low-lying cities such as Huntington Beach will flood more frequently and more severely.
• More than 42,000 homes in California will be under water — not merely flooded, but with seawater over roofs.

The grim outlook is mirrored in the latest report, which is being presented April 26 for adoption by the state’s Ocean Protection Council. Its sea-level rise projections will assist state agencies and local governments with planning.

No stretch of the state’s 3,400 miles of coast, bays, inlets and islands will be spared. Addressing sea-level rise will cost a staggering amount of public and private money, and will particularly impact the poor and vulnerable. The problem becomes more urgent with much of California’s wealth huddled along the coast, supporting an ocean-dependent $44 billion economy.

In the end, state and local officials may come to the gut-wrenching conclusion that some coastal land should be simply abandoned.

“We’re not doing well at all,” said Democratic Assemblyman Mark Stone, chairman of the Select Committee on Coastal Protection and Access to Natural Resources. “We have yet to really start to answer the hard questions and make policy — saying, ‘No, we are not going to put public money here.’ Eventually we should get to the point that we are not going to do any public investment in those places any more.”

Most scientists tread lightly in the policy realm, providing the information for others to craft into regulations. Not Bill Patzert, who has for years sounded the alarm about rising oceans.

“It’s not an existential threat. It’s real. It’s gonna happen,” said Patzert, a climatologist at NASA’s Jet Propulsion Laboratory. “Here’s the bigger issue: If you’re in the tunnel and you see the train coming at you, what do you do? Do you race towards it or do you back out? It’s just common sense. As a society, why aren’t we doing that?”

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How high will it go? Check sea level rise near your neighborhood
Scientists use maps such as this to help state and local officials plan for sea level rise and associated flooding. This interactive graphic shows potential flood zones with water up to 10 feet, the outer range of current projections. (Map by Climate Central)

From deep in the hive of large brains at the Jet Propulsion Laboratory in Pasadena, set hard against the San Gabriel Mountains, an intense group of scientists from Caltech and the NASA are harnessing satellites that for decades have been peering into space and are now directing their gaze to Earth.

The researchers — with advanced degrees in physics, mathematics and oceanography — are engaged in what many consider to be the critical research of our time.

They are watching ice melt.

Sitting alone in a cubicle, bathed in the glow of a computer screen or staring down the barrel of a telescope, can be a balm for scientists. Concerning themselves with one finite slice of a planet-wide catastrophe allows them to compartmentalize and disengage from the entire sobering picture.

But even professional detachment fails against the unfolding horror show depicted in the cold display of satellite imagery.

“We are in the process of watching the ice sheet in Greenland disappear,” said the lab’s oceanographer Josh Willis, who leads a team studying Greenland. “This is the first time humans have been able to measure it. The last time it was shrinking at this rate was tens of thousands of years ago.”

The diminishment of Greenland’s ice mass has been accelerating alarmingly, losing a trillion tons in the last four years. The rapid melting is getting the attention of scientists because locked away in the Greenland ice sheet is the possibility to raise global sea levels by 24 feet. The Antarctic holds 187 feet of potential ice melt. Polar ice loss on that scale would have unfathomable consequences for continued life on Earth.

Willis uses satellites to measure the warmth of the waters around Greenland. Because he has a sense of humor, his project is known to all as OMG: Oceans Melting Greenland. (He preferred calling it Water Temperature Fjords, but couldn’t get the acronym past government sensibilities.)

“As scientists, we’re witnessing these huge events, and it’s telling us how the Earth is changing,” Willis said. “Of course, I’m also a citizen, I live on this planet, and it is worrying that it’s happening. It’s sometimes profoundly shocking to wake up and realize we’re reshaping our entire planet.”

Understanding the threat of sea-level rise in California depends to some extent on where you are standing: Boots in the dust of the Central Valley and you might curse the lateness of a rail shipment held up by flooding at the port of Oakland; bare feet in the sand at Huntington Beach and you may have to consider relocating your family, your home and all your possessions.

Some simple math: Every inch of sea-level rise equates to an 8- to 10-feet loss of beach. So, using the conservative projection of a 4-foot rise, and the lower-end 8-foot-per inch formula, that equates to 384 feet of coastal beach loss in the next 70 years.

The 10-foot rise scenario, which scientists peg as the new worst-case, would cause a land loss of 800 feet — the length of two-and-a-half football fields. The sea will not rise the same amount in every place; scientists say each discrete elevation is dependent on factors such as the shape of the sea floor and the slope of the landfall.

Considering the scope of this coming catastrophe, it does not appear to be front-of-mind to many in the state. But that doesn’t mean it’s gone unstudied. California has a peerless capacity to turn over problems until they are smooth and shiny. Understanding comes first, with action often a distant and expensive second.

A tour through recent scientific analyses:

A 2009 report on sea-level rise commissioned by the state paints worst-case scenarios that are the stuff of disaster movies: A half-million Californians at risk of flooding and more than $100 billion worth of infrastructure. More than two dozen coastal power plants flooded, along with hundreds of hazardous waste facilities, as well as schools, hospitals, police stations, ports and major airports.

A 2012 report prepared for the California Energy Commission focused just on the San Francisco Bay and its 1,000 miles of shoreline, concluding: “Rising sea levels will overwhelm the existing protection structures, putting the 140,000 people currently living in vulnerable areas at increased risk.” The authors cautioned their findings did not reflect worst-case scenarios. And, if no action is taken to address the vulnerabilities, the risk projections should be considered “substantially low.”

The California Assembly weighed in with a report in 2014, and the next year the Senate chimed in with its own review, amping it up a bit: “With current projections, rising seas combined with a 100-year flood event would close over 2,000 miles of roadway, the Oakland and San Francisco airports, and the Port of Oakland.”

The sobering fact of those state-of-the-art reports, recent though they are, is that they are already out of date and not nearly comprehensive enough in describing the scope of what currently faces California. Nor remotely scary enough. What scientists are observing now is, they say, a rapid and steep change that, even as it unfolds over comparatively long periods of time, is nonetheless occurring at a breathtaking pace.

Sea-level rise is caused primarily by two factors related to global warming: the expansion of seawater as it heats up and the added water volume from melting ice. Researchers focused on glacial melt in Greenland and Antarctica see the process as an action-packed cataclysm marked by heaving ice shelves collapsing into the sea and sheets of decaying ice sloughing off the end of a continent.

The power unleashed by that tide of ice is awesome to contemplate. Water has always been one of the most destructive and transformative forces in nature. With warmer waters creating more energy that incubates more powerful storms, some see a near future in which seas assault our coast more frequently and with greater force. Exhibit A: California’s past winter, when repeated storms lashed the state, resulting in a preliminary price tag of $569 million and a federal disaster declaration.

Scientists warn that intensified El Nino events, coupled with higher seas, will bring about unprecedented flooding. What civil engineers refer to as nuisance flooding — overwhelmed storm sewers and street flooding — is already more common. King Tides are getting worse. Commuting times, the ability of first-responders to get to an accident scene, and the transportation of goods by road will be severely compromised, researchers say.

That risk, too, can be observed at its point of origin. The National Oceanic and Atmospheric Administration (NOAA) maintains tide gauges that bob and float in U.S. waters, sentinels sending out a stream of data measuring current sea levels. The information feeds tidal forecasts used by surfers and mariners, and is also monitored by emergency services.

The tide and currents map is both colorful and alarming. The maps depict the North American continent ringed by arrows pointing straight up, denoting trending rising sea levels, like pickets defending the coast.

It turns out the coast is all-but defenseless.

Brett Sanders, a civil and environmental engineer at UC Irvine, is using a grant from the National Science Foundation to help inform communities along the California and northern Mexican coast about the risk of rising waters. Most people are thrilled that they’ve managed to fulfill a dream of living near the beach, Sanders said, and are unaware of what they should do to protect themselves.

“We have done a bad job of mapping flood risk. It’s awful,” Sanders said.

Zillow, the website that calculates residential real estate values, recently took its maps of coastal property and overlaid NOAA’s sea-level projections. Using what are now thought to be conservative projections, the company estimated 2 million coastal homes in the United States would be underwater by the end of the century. Not as in being upside down on a mortgage, but as in fish swimming through the den. The total value of those homes? Nearly $1 trillion, in California, $49 billion.

Zillow’s chief economist, Svenja Gudell, said she was surprised that when the company shared its information with mayors or city planners, officials saw it as an event that would take place far in the future. “For some of these places the time horizon is not 100 years, it’s happening now,” she said. “It’s not as top of mind as it should be or you would like it to be. People are underinsured when it comes to flood insurance. The system is broken.”

Gudell said that her research showed that homeowners living in high-risk areas are not getting market cues —real estate values in beach areas destroyed by Hurricane Sandy are now higher than before the superstorm that played out on national television in the fall of 2012.

“We were not able to explain that rationally,” Gudell said. “We will see in the future, if you are on a cliff and that cliff is further eroding and if you put a piece of property on that land, it won’t be safe anymore. For now, the benefit of living in these homes clearly outweighs the current and future cost of living there.”

Which leaves us with the National Flood Insurance Program, a troubled and debt-ridden program operated by the Federal Emergency Management Agency. The flood insurance covers millions of Americans living in flood zones, based on maps that are decades out of date. The program is currently $24 billion in debt and requires reauthorization from Congress.

Critics of the federal insurance say the rates don’t reflect current risks, leaving taxpayers on the hook for someone else’s folly.

Democratic state Sen. Henry Stern represents a coastal district that includes Malibu and a string of state beaches. A lifelong surfer, he understands the attraction.

“It’s so alluring,” he said of living by the beach. “But my whole thing is to make the market tell the truth about it. We know where sea level rise is going to happen. What I don’t want to happen is for all of us to bear the bill afterwards.”

Even with the horrific projections scientists have repeatedly shared about public health and safety associated with rising seas, it might be the economic cost that spurs action. A 2016 paper published in the journal Nature estimated the annual global cost for sea-level rise adaptation measures at about $421 billion per year.

The authors of the study argue that the figure doesn’t take into account population growth and clustering around coasts. By the year 2100, the report warns, the price tag for mass relocations could exceed $14 trillion. Given California’s coastal population clusters — 75 percent of the state’s residents live in a coastal county — the figure here will be enormous.

The Ocean Protection Council receiving the new science report is a state agency whose mission, as its name implies, is to look after the welfare of California’s piece of the Pacific Ocean. It’s an almost laughably large responsibility, and one that the members approach thoughtfully.

The report placed the scientific findings at the forefront, said Liz Whiteman, the science and strategy director for the Ocean Science Trust, which was a partner in the study. That means the analysis does not entertain the question of whether climate change is altering the behavior of the Pacific. Nor does it belabor stale arguments about how weather has always changed. It is, rather, an unsparing document that presents the best projections about the range of sea rise, and, for the first time, assigns a probability and risk to those numbers.

“California is in a great place for being willing to call the hard question and not shying away,” Whiteman said. “There is no doubt that there is some scary information contained in a report looking at sea-level rise and our future.”

Dan Cayan, one of seven scientists who contributed to the newest report, is a researcher at Scripps Institution of Oceanography, investigating how climate affects changes in oceans. Viewed from his office window in La Jolla, the Pacific Ocean appears benign and soothing. But a glimpse into the updated information he’s assembling paints a different, darker picture.

New data and more sophisticated modeling, he said, coupled with more extreme climate warming, “Is going to be pushing the amount of sea-level rise above what was thought to be reasonable.”

Comparing previous projections to current ones, he said, is no longer useful. “We’re actually off this scale,” he said.

Cayan pulls out the 2012 report from the National Research Council, which is the basis for California’s current sea-level rise assumptions and the predicate for the state’s coastal policies. The mid-range of its projections envisions about 3 feet of rise by 2100.

Then he carefully takes out a sheet with the new data. Cayan points at the the elaborate graphs to the updated mid-range projection— 8½ feet. Cayan and his colleagues shrug off questions about how to apply their science—that’s the job of the politicians. But the report does counsel state officials to consider the worst-case scenario in their deliberations, and cautions: “Waiting for scientific certainty is neither a safe nor prudent option.”

So what now? California planners and policymakers will pore over the latest report. Their deliberations will result, at some point, in “updated guidance” to use the parlance of the bureaucracy. The final document will help local officials incorporate the sea-level rise projections into their future plans for building and safety, in some cases altering zoning and building codes.

Meanwhile, Greenland’s summer ice melt season begins, and the 2-mile deep ice sheet that was created in the last Ice Age continues to shrink. Researchers drilling ice cores have been astounded to find more and more streams of water rushing below the sheet—a river of water scything through ice. The proliferation of these ‘melt streams’ is leading scientists to consider that the loss of Greenland’s ice may be set on an unstoppable trajectory.

No longer a matter of if, but only of when.

This is the first in a series: Next up — how is California planning for the seemingly inevitable. CALmatters.org is a nonprofit, nonpartisan media venture explaining California policies and politics.