New Federal Report Warns of Accelerating Impacts From Sea Level Rise

The global average sea level is rising 2 inches per decade and speeding up, but in some regions, the rate is more than twice that fast.

During the high tide the inhabitants of Ghoramara Island in India are fixing the fragile soil embankment to restrain the further land erosion and the high tide that inundates to the island that is rapidly disappearing due to the sea level rise. Credit: Debsuddha Banerjee / Climate Visuals Countdown

During the high tide the inhabitants of Ghoramara Island in India are fixing the fragile soil embankment to restrain the further land erosion and the high tide that inundates to the island that is rapidly disappearing due to the sea level rise. Credit: Debsuddha Banerjee / Climate Visuals Countdown

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SAN AGUSTINILLO, Mexico—As the rising ocean encroaches on the small spit of sand connecting San Agustinillo’s beaches to the rocky headland along Mexico’s southern coast, local fishermen say it’s getting harder to find a place to beach their outboard-powered skiffs after catching snapper, tuna and dorado in the warm Pacific waters. 

With no harbor, the boats speed out of the water and onto the sand, the driver yanking the propeller out as the bow hits dry beach.

High tides during the last couple of years have regularly cut steep bluffs from the sand, sometimes making it almost impossible to get all the boats ashore, said Anam Cruz, who has been catching fish for his family and community for 26 years. The boats for whale, dolphin and turtle spotting can also be marooned, eating into Mexico’s economically important tourism industry.

“This is new. I know the sea is coming up, but nobody told us the beaches would change this much,” Cruz said. “Sometimes now, we can’t catch fish. It only used to be like this for a few weeks after big hurricanes in the rainy season, maybe every five years.” 

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But global warming is speeding up geological change to a pace tangible in the span of a lifetime, or even a few years. 

Many residents of coastal Southern Mexico don’t know that the sea around them is likely to rise another 15 to 20 inches in just the next 30 years.

Those projections were confirmed Tuesday by an updated report from the National Oceanic and Atmospheric Administration and NASA using new satellite data and climate models along with improved evaluations of historic data from tide gauges dating back more than 100 years. 

“What we’re reporting today is historic,” said NOAA administrator Rick Spinrad, who told Americans that, on average, sea level at their coasts will climb 10 to 12 inches in the next 30 years and 2 feet by the end of the century. 

“And that estimate is on the conservative side,” he said. “Failing to curb emissions will cause even greater impacts.”

Like Cruz, Nicole LeBoeuf, director of NOAA’s National Ocean Service, has witnessed the accelerating sea level rise during her lifetime.

“I grew up on the Texas Gulf Coast, and we know the ocean and the shore always change,” she said. “These are not the kinds of changes we grew up with.” 

She warned of a “profound increase in coastal flooding with storms or heavy rainfall … and high tide flooding.”

Urgency for Adaptation

The report confirms that “things are going to get bad fast,” said Andrea Dutton, a sea level rise researcher at the University of Wisconsin, Madison. She said the report shows there will be a major shift in flooding patterns on U.S. coastlines by 2050 driven largely by sea level rise.

“That kind of language, that’s NOAA sending a red flag warning up,” she said. “We’re grappling now, trying to catch up to the changes that have happened, but because it’s accelerated it’s going to be a whole other level that we’re dealing with. We can see this freight train coming from more than a mile away.”

Dutton said the report also raises concerns about sea level “tipping points,” including a rapid increase in the melting of polar ice shelves, that could spur a much faster rise. If the frozen ice shelves around Antarctica start losing stability, or if ice cliffs start fracturing off in huge slabs, “the system goes past a threshold,” she said, “and you can’t stop this.” 

“Right now, we’re measuring sea level rise in millimeters per year. If we cross those tipping points, it will be centimeters per year,” she said. “You never know where the tipping point is until you pass it, and right now it looks like we are at, or very close to more marine ice sheet instability.”

But the tipping point is clearly close enough that everything possible should be done to prevent Antarctic ice shelves from retreating farther, she said.

And there are also land-based tipping points related to sea level, she continued. While sea level rises gradually, it’s already close to much of the coastal infrastructure in the U.S., with sea water inundating drainage systems and even some drinking water supplies.

Along some coasts, natural features like dunes and marshes may be holding back the sea a bit, but once the sea rises above those, it can spread inland, a big concern for Florida, where a lot of territory is barely above sea level.

“We’re filled to the brim,” Dutton said. “And if you get over the lip it can go a long way.”

Flood of Emotions

Along with the direct physical impacts, Dutton said it might be time to start thinking about sea level rise in the context of loss, grieving and acceptance.

“It’s like when you first realize as a kid that people die someday,” she said. “Accepting that the future is going to look and be different is a first step. Sometimes I feel like, instead of the science and engineering, we should be putting money into grief counseling for coastal communities.”

The report includes a detailed map for sea level rise, and federal agencies and researchers have other tools that can show how rising sea levels affect American coastal communities block by block. There are well-known, if expensive, ways to protect some places, with floodwalls, dikes or levees, or with restored coastal ecosystems like marshes and mangrove forests.

“The coastline is going to move,” Dutton said, adding that some places simply won’t be able to persist.

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Much of the information in the report was distributed broadly around the world as part of the Intergovernmental Panel on Climate Change’s report on the physical basis of climate change last summer, which vividly showed that no coastal area of the world is safe from rising seas and other threats from global warming.

But that doesn’t mean the information is going where it needs to, and even if it does, many countries don’t have the resources to prepare for the rising waters. The nations that are least capable of holding back the flood are often those that have produced the smallest amounts of the climate-warming emissions that are swelling the oceans.

The International Federation of Red Cross and Red Crescent Societies (IFRC) documented coastal impacts in a recent report called Turning the Tide that describes abandoned coastal villages in the Mexican state of Tabasco, where there are few resources for relocation. 

Some of the few people remaining now have to shore up the foundations of their houses every day. In Bangladesh, the relief agency described a family that has already lost its home three times to the rising waters. Some villages there now remain flooded for many months after tropical cyclones hit.

For some island nations, the updated report from the U.S. science agencies confirms the death sentence that was handed down years ago. Even if greenhouse gas emissions stopped tomorrow, Pacific atoll islands such as Kiribati, the Marshall Islands, Tuvalu and the Maldives, in a region where sea level is rising 2 to 3 times faster than the global average, are in danger of disappearing over the coming decades.

In a 2019 report, the IPCC warned that sea level was 20 to 30 feet higher than today during past geologic eras when the global average temperature was just 1 to 1.5 degrees Celsius warmer than it is currently—temperatures that the planet will exceed if it continues on its current trajectory of heating. 

Trickling Down Through Coastal Ecosystems

In coastal Oaxaca, biologists say it’s not just humans that have to worry about global warming and sea level rise. The rapid changes are threatening sea turtles, which have been around for more than 100 million years by adapting to mega-climate changes that happened on a slower, geologic time scale.

But as sea level races up faster than the beaches can reconfigure themselves, the same sand cliffs that frustrate the fishing boats also hamper some of the turtles from crawling to their breeding sites. Studies show that increasing beach erosion is a key threat to sea turtle breeding globally. 

In some cases, researchers have also documented that turtles seem to be crawling  farther from the ocean to get away from the encroaching water, but that can lead them to dig their nests in much warmer sand, which affects how many eggs hatch and the gender of the hatchlings. If it gets too warm, some turtles could go extinct because too few males hatch.

Coastal bird nesting areas in marshes are also being swamped by the ocean, and because human developments have already changed many estuaries, there aren’t a lot of options left for some species. The U.S. Geological Survey is tracking several small mammal species in coastal marshes that may soon go extinct.

A warming, climbing ocean is affecting sea turtle breeding already, and sea level could go up as much as another 15 to 20 inches by mid-century if carbon emissions don't decrease soon. In some places, the turtles are climbing far from the sea to a hotter section of the beach where reproduction is more challenging. Credit: Bob Berwyn
A warming, climbing ocean is affecting sea turtle breeding already, and sea level could go up as much as another 15 to 20 inches by mid-century if carbon emissions don’t decrease soon. In some places, the turtles are climbing far from the sea to a hotter section of the beach where reproduction is more challenging. Credit: Bob Berwyn

Other research suggests that rapid sea level rise could wipe out coastal mangrove forests that currently protect shoreline communities. Mangroves also suck a lot of carbon dioxide from the air, so their loss also would cause greenhouse gas levels to increase and further warm the climate.

The new federal report improves confidence in projecting the rates of sea level rise, especially for the next 30 years, said Natalie Snider, Environmental Defense Fund vice president for climate resilient coasts and watersheds. That’s important for near-term decisions about how to protect people and ecosystems.

“A lot is also going into thinking about how some communities are not going to be able to stay where they are,” she said. “Some people have already reached their tipping point, mostly well-off white people, in some places leaving behind a disadvantaged population that doesn’t have the capacity to move.”