If the city of San Diego does nothing, in 80 years ocean waves will probably flood Mission Beach’s iconic boardwalk, lapping dangerously close to Belmont Park’s Giant Dipper roller coaster. Homes and businesses along portions of Neptune Avenue in La Jolla will lose their beachfront, threatening the already crumbling cliffs.

And that’s the best-case scenario, according to San Diego’s sea-level rise vulnerability assessment, a report quietly published on Christmas Eve on the city’s website.

Worst-case scenario? The Pacific Ocean could swallow up to 90 percent of San Diego’s beaches, 60 percent of its hotels, motels and restaurants, and a huge chunk of its water infrastructure over the coming century.

Whole portions of the city could crumble away in just decades, especially during storms when tidelines surge well past existing sea walls and other coastal infrastructure.

The report’s seemingly apocalyptic findings make no mention of cost. There’s no quantifying of damage to property and infrastructure, disruption to city services or insurance liability. In fact, there’s only one dollar sign in the 56-page document, a reference to nearly 10 percent of households in San Diego earning over $200,000 annually.

That means the city, in its sea-level rise assessment, has not yet answered who will pay for these local impacts brought on by the demands of a global economy. Likewise, the report does not describe the cost of doing nothing.

“What we have right now is a high-level cost estimate if we do nothing,” said Heidi Vonblum, environmental policy program manager in the city planning department. “But that’s not the plan.”

The city declined to provide that total estimate, citing the complexity of attaching a dollar figure to the threat sea-level rise poses.

But the city has formally estimated a portion of those costs in another report, on the impact to state land within city limits. In that report, the city said rising seas could cause $335 million in damages to state land in San Diego by 2030 if the city takes no action. And that’s without factoring in ocean surges during storms. State lands, however, represent only a “small subset” of San Diego property, the report states.

What infrastructure will be exposed to flooding? Worst-case scenario: No global slowdown of fossil fuel use, the Arctic as well as a large portion of Antarctica melts and the city takes no action. Just under 80 percent of lifeguard stations

Just under 40 percent of wastewater pipes

About 85 percent of wastewater pump stations

Just under 60 percent of drain pump stations

About 50 percent of stormwater outfalls

Over 60 percent of the city’s 1,291 acres of marshland

Over 70 percent of the city’s beaches – and almost 90 percent during storms

Eleven historic and cultural resources are threatened by flooding (during storms) at about one foot of sea-level rise.

Worst-case scenario: What are the economic impacts? Over 90 percent of the city’s 45 marina docks are already exposed to flooding at the ocean’s current level.

Just under 60 percent of all hotels and motels

About 15 percent of restaurants

The Science Is Uncertain, but the Direction Isn’t

There are still many unknowns and uncertainties surrounding what science can tell us now about our future world. A lot depends on how quickly the global economy (and population) can adapt to life and commerce without burning excessive amounts of fossil fuels.

The amount of sea-level rise depends roughly on how much global temperatures spike and ice in the Arctic and Antarctic melt.

The oceans actually suck up a lot of the heat that would otherwise go into the atmosphere, preventing a quicker heating of the planet (thank you, mother ocean). But when water warms, it expands, another reason why high tides are getting higher and January’s so-called king tides wash over more of Imperial Beach than before. (King tides occur a few times a year when the moon, sun and earth align, causing tides to be much larger than usual, often causing significant flooding.)

There’s also a wide forecast when it comes to how much water San Diego will have to wrangle. How fast the sea will rise and how high it will get in California over the next century “are uncertain, though the direction of change is not,” as the state’s 2018 sea-level rise guidance document put it.

So cities like San Diego are trying to make their best guess based on available science.

Globally, the average rate of sea-level rise is seven-tenths of an inch per decade, more than twice the average rate since the industrial revolution and the mass burning of fossil fuels began in the 1900s.

In San Diego, the situation is more dire.

Over the last century, the ocean around San Diego rose about one inch per decade.

It’s hard to wrap your head around what seems like a tiny change, but that means the ocean around San Diego is rising 32 percent higher than the global average, according to the National Oceanic and Atmospheric Administration. The reasons why have to do with Earth’s gravity and ocean currents and nothing to do with climate change, said Helen Fricker, a glaciologist at Scripps Institution of Oceanography.

So, under the “worst-case scenario,” by 2030 San Diego could see up to a foot more water, up to about 3 feet more by 2050 and by 2100, over 10 feet.

But even that scenario doesn’t account for another possibility. Scientists identified an unstable situation in eastern Antarctica that could potentially unleash five more feet to global estimates, the Washington Post reported Monday.

“The immediate threat of sea-level rise is there. It’s not going to happen tomorrow or next week but it probably will in a few years,” Fricker said. “We should be planning for it now so we’re not overwhelmed.”

Fricker worked on a report to California’s governor on rising seas, in which she said there’s a 50 percent chance the ocean will rise over a foot in La Jolla by 2100. Fricker says she wouldn’t buy a house at sea-level right now.

“We should be preparing for the worst and hoping for the best,” Fricker said. “It’s a bit like flattening the curve with this (COVID-19) pandemic. We’re going to get a lot of ice coming off Antarctica, it’s just a matter of how much and how quickly.”

How the Cliffs Will Crumble

How much and where the beach and cliffs will crumble is also hard to predict.

It doesn’t really matter, though, because research by scientists at Scripps Institution of Oceanography suggests where a cliff once crumbled in the past is not a good predictor of where it will crumble in the future.

Under the best climate change scenario – if all the global powers collectively cut emissions – San Diego may still lose 31 percent of its beaches at the end of the century, the report states.

Beach nourishment, a fancy term for piling more sand on a beach, is a common Band-Aid to the problem of shrinking shorelines. It’s a popular solution in places like Imperial Beach where king tides already creep into beach houses and city streets, backing up sewer systems and sucking sand back into the depths.

San Diego’s report essentially says beach nourishment won’t work in the future as the seas swell from climate change. That leaves few options for cities to adapt to unstoppable nature, the least unpopular of which is “managed retreat,” a bureaucratic term for abandoning or moving your property and livelihoods elsewhere.

Tallying the Cost

The cost of climate change is hard to calculate. It’s a cataclysm that touches almost every aspect of human, animal and plant life on the planet.

For some context, a new South Mission Beach lifeguard station (a more permanent structure than the traditional hoisted plastic capsule towers) cost $4.9 million. Vonblum, from the planning department, said that tower was actually designed to withstand rising seas. Its equipment lives on the higher floors, and the city added barriers to control erosion.

Another report that should shed light on how much of a blow sea-level rise, and climate change more generally, poses to the city’s infrastructure gives no hints on costs.

A 197-page staff report dated Feb. 25 to the Public Facilities Financing Authority, which authorizes the city to issue bonds, take out loans and draw down debt, discloses the city’s risks to investors. Investing in city infrastructure is safe for investors, because city projects are typically backed by taxpayers, a reliable stream of cash.

The report summarizes its climate change risks in four paragraphs and, in a document riddled with dollar signs, not a one appears there. Its warning is plain, but unspecific: “Initial findings of the assessment identify increasing exposure of assets from now through the end of the century.”

Dan Rabasco, a Boston-based head of municipal bonds at Mellon Investments, warned against precisely that type of generic risk assessment. He told the Financial Times on Jan. 7 that government borrowers need to start spelling out their climate change resilience plans explicitly.

“What plans are they making? Are they hardening their infrastructure … Are they trying to insulate central services?” he said. “If they’re just stating the obvious, that’s not sufficient.”

San Diego is mandated by the state to have a plan on how it will adapt and survive the climate crisis by 2022.

“The information we have available to us shows that every dollar we spend on mitigation (and adapting) to climate change saves four dollars we would spend on the ‘do-nothing’ approach,” said Vonblum.