Big Waves and High Tides Can Be Just as Insidious as Hurricanes

Mint

13-06-2025

(Bloomberg Opinion) -- A couple of days before Christmas last year, battered by heavy waves, the end of the half-mile-long Santa Cruz Municipal Wharf unexpectedly tumbled into Monterey Bay.
A tourist magnet claiming to be the longest fully wooden structure of its kind in the Western hemisphere, the wharf was open for business when the collapse happened, forcing visitors and workers to evacuate. Two engineers and a project manager at the wharf's terminus fell in the water but escaped serious injury. Some heavy construction equipment and a large public restroom weren't so lucky.
The collapse, triggered by waves that may have been up to 30 feet high, came just a year after another winter storm had damaged the same section of pier (a storm that came one year after another winter storm hit Monterey Bay). The construction equipment and workers were there to help with repairs. For much of the past decade, Santa Cruz had planned wharf upgrades that included a 'landmark' building on the section that fell in the drink. Now even the idea of simply restoring the missing part of the wharf, a $14 million project, is up for debate.
Santa Cruz isn't alone. Cities on every coast face hard, expensive decisions about rebuilding damaged neighborhoods and piers, relocating scenic roads, train lines and other infrastructure and otherwise battling waters that are becoming higher and more destructive as the planet gets hotter.
When we talk about climate-fueled ocean disasters, we usually talk about either powerful hurricanes or the slow but steady rise of ocean levels as polar ice melts. But the more mundane effects of a warming planet are just as insidious, and they're already here, tossing us and our bathrooms into the ocean and demanding a response before we're ready.
'Most states and countries are trying to project sea-level rise. Meanwhile, large waves and high tides are already beating up the shoreline,' Gary Griggs, a professor of earth and planetary sciences at the University of California, Santa Cruz, told me. He recently published a paper in the Journal of Marine Science and Engineering pointing out that, while current sea-level rise of 4 millimeters a year — about the width of two nickels — is a slow-motion disaster, we're not prepared for the faster catastrophes happening now. 'Twenty-eight-foot waves and 7-foot tides overpower everything just like a Hurricane Sandy.'
Though waves don't get nearly as much attention as sea-level rise, studies suggest they're growing bigger and more powerful as a result of climate change. The idea is that a warmer sea surface generates faster winds, which in turn drive higher waves that also produce more energy. A 2019 study by a UC Santa Cruz associate professor, Borja Reguero, and others used satellite data and modeling to suggest waves had grown 0.47% more powerful each year (or about 1 megawatt per meter per year) between 1948 and 2008 and then 2.3% each year between 1994 and 2017. Two separate studies last year in the journal Applied Energy found similar results.
A fun thing to know about waves is that they create tiny earthquakes every time they slam into shore. A 2023 study by Peter Bromirski, a researcher at the Scripps Institution of Oceanography at UC San Diego, used decades of seismic data from the California coast to show that waves have become taller since global heating started accelerating in the 1970s.
The 8 to 9 inches the oceans have risen since 1880 may not sound much scarier than those two nickels' worth of annual increase. That's barely enough to splash your calves at the beach. But the rate of increase has accelerated since roughly the early 1990s; about half of all sea-level rise has occurred since 1993. Maybe not coincidentally, the growth in wave power accelerated around the same time.
Higher seas are a force multiplier for those bigger waves. They also make high tides higher and more destructive, boosting the risk of 'sunny day flooding' on many coasts. High-tide flooding has increased by more than 400% on the southeast Atlantic coast and 1,100% on the Gulf Coast since 2000, according to the National Oceanic and Atmospheric Administration.
More than 900 critical infrastructure assets in the US, including schools, public housing, power plants, fire stations, hospitals and more, were at risk of flooding at least twice a year in 2020, according to a study last year by the Union of Concerned Scientists. That could rise 20% by the end of the decade. Hundreds of thousands of coastal homes, meanwhile, are at increasing risk of chronic flooding, according to an earlier UCS study, helping fuel our national insurance crisis.
Once upon a time, Griggs told me, you could chalk up the most damaging California storms to El Niño events, which raise Pacific water levels. But El Niño was only in place during the 2023-24 storm season. The storms one year before and after that formed under supposedly calmer La Niña conditions. Climate change may make El Niños stronger or more frequent; the jury is still out. But you don't need an El Niño to get a destructive surf. All you need is a little sea-level rise, bigger waves and a high tide. Those factors also make hurricanes more destructive, as happened with Hurricane Sandy, which hit during a full moon that made tides higher.
Even if all fossil fuels were miraculously raptured out of existence overnight, thus cutting off the primary source of the greenhouse gases heating up the atmosphere, their effects on the ocean would linger. As it stands, we're on course for all of these factors to worsen in the decades to come. They're already bad enough, and the example of the Santa Cruz Wharf shows we're not ready.
President Donald Trump isn't helping by cutting off billions in Federal Emergency Management Agency (RIP) grants to harden homes, buildings and infrastructure against natural disasters. He has even frozen funding from the Building Resilient Infrastructure and Communities program, part of a law signed in 2018 by the overly woke … President Trump.
Perhaps Trump has what Griggs terms 'disaster amnesia,' the affliction gripping many people who rush to rebuild after disasters without considering the possibility of another one. Or who open an already-surf-damaged wharf to people during another pounding surf. Amnesia is less likely when the disasters happen year after year. Hopefully they might even foster something like foresight. That's our best hope at making them much less costly.
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This column reflects the personal views of the author and does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
Mark Gongloff is a Bloomberg Opinion editor and columnist covering climate change. He previously worked for Fortune.com, the Huffington Post and the Wall Street Journal.
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