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New U.S. sea rise projections are lower but still forecast grim future for Florida

flooded street
Emily Michot
Miami Herald
A lone car is parked on a flooded street near the intersection of Northeast Bayshore Drive and Northeast 78th Road Tuesday afternoon, Nov. 9, 2021. The flooded streets were due to King Tides. This level of flooding could be much more common by mid-century as sea levels rise.

As attention and urgency ramp up around the world over the looming dangers of climate change, a major new federal report released on Tuesday offers a surprising forecast: It actually reduces the amount of sea level rise the world is expected to see as the Earth warms.

As attention and urgency ramp up around the world over the looming dangers of climate change, a major new federal report released on Tuesday offers a surprising forecast: It actually reduces the amount of sea level rise the world is expected to see as the Earth warms.

For South Florida, the region with the most coastal real estate at risk, the sobering prediction is that the sea will continue to rise — about 11 inches by 2040 — but the latest forecast is markedly less than atmospheric modeling runs produced just five years ago. That previous forecast called for 17 inches by 2040, a level likely to produce regular and damaging tidal flooding in low-lying areas from Key West to Palm Beach County and beyond.

It’s a change that really only amounts to a bit more breathing room, said Jayantha Obeysekara, head of Florida International University’s Sea Level Solutions Center and contributor to the report. The end of the century scenarios are still bleak for Florida — five to seven feet at the new worse case projections.

“We have a little bit longer time to act,” he said, “more time to prepare for something bigger, later.”

The National Oceanic and Atmospheric Administration report, issued every five years, produced a range of potential sea rise scenarios for the nation’s coastlines. The biggest changes in the updated forecast were in the higher range scenarios, which got significantly lower in Florida — largely the result, scientists say, of better data.

Ben Hamlington, co-author of the report and a researcher with NASA’s Jet Propulsion Laboratory, said the latest report included intensive new research on the threat of melting ice sheets and glaciers in Antarctica, including the one nicknamed the “Doomsday glacier.”

“These scenarios really do capture the latest and greatest in science,” he said. “We have a little more confidence, regardless of emissions, what window we’re going to fit through by 2050.”

In one other significant change, the new report also axed the apocalyptic “extreme” scenario that called for 10 feet of sea rise by century’s end. The least amount of change came in low-end forecasts, which aren’t often used for planning in this state. Overall, NOAA scientists said the refinements indicate growing confidence for what to expect in the next 30 years, which should help politicians and planners scrambling to adapt to rising seas.

William Sweet, co-author of the report and a researcher with NOAA’s National Ocean Service, stressed that the report confirmed that rising seas remain a massive challenge for most coastal communities, which will still face increased risks of potentially devastating flooding from storm surge and high tides.

“There is less sea level rise than projected in a previous report, but hitting those scenarios I’m not sure I’d say that’s good news,” he said.

Chart shows projected rise in sea levels

On a press call to announce the new report, NOAA administrator Richard Spinrad said it suggests that sea levels will rise globally about a foot by mid-century, and slightly above that along the U.S. East Coast and Gulf Coast.

“This report is a wake-up call to Americans, but a wake-up call that comes with a silver lining,” he said. “It provides us with information needed to act now to best position ourselves for the future.”

Sea level rise is perhaps Florida’s greatest threat from climate change. It threatens to erase billions of dollars in property value and thousands of homes in coming decades. As the waters creep higher, they’re already breaking the human-waste-filled septic tanks Floridians rely on, polluting major water bodies and threatening human health.

Sea rise also directly impacts how much damage hurricanes can do. A higher sea level means more water gets pushed ashore during a storm, which is the deadliest aspect of a hurricane.

For the first time, Florida has begun mounting a serious effort at helping local governments address the problem by raising roads and buildings, installing flood pumps and getting rid of the leaky septic tanks. In the past few months, Gov. Ron DeSantis announced more than $670 million in funding over the next three years from federal and state sources. But many scientists say resilience alone doesn’t go far enough and that Florida, along with other states and nations, will need to dramatically cut the root cause of climate change — emissions from burning fossil fuels.

Scientists say that cutting emissions now won’t stop sea rise immediately, since the atmosphere is already pretty warm, but it will make a difference later in the century. Spinrad said that there’s a certain amount of sea level rise that’s bound to happen by 2050.

“Current and future emissions matter, but this will happen no matter what we do about emissions,” he said.

Sweet, the report co-author, said the reason why the higher projections were more affected than lower projections in the new report is because the higher projections rely more heavily on those glaciers and ice sheets melting, and new research suggests that’s less likely than scientists thought in 2017.

Dinosaur ride in a flooded park
Emily Michot
Miami Herald
No children were playing on the dinosaur or pony ride at the Little River Pocket Mini Park Tuesday afternoon, Nov. 9, 2021, after the park was flooded with King Tide waters. This type of flooding could be much more common in the future as sea levels rise.

“The whole idea of ‘where ice melts matters’ is quite relevant when it comes to how global sea rise manifests itself,” he said.

Another update in the new report is a set of projections for future sea level rise that focus far more on how sea rise has already risen. For Florida, that set of predictions is pretty close to the new intermediate high NOAA projection.

Currently, South Florida governments rely on two projections for sea rise to decide where and how high to build. The higher one is the 2017 NOAA intermediate-high standard, which called for 17 inches of sea rise by 2040, and the United Nation’s Intergovernmental Panel on Climate Change’s median projection, which called for 10 inches of sea rise by 2040. The new NOAA projection, based on readings from the Key West tidal gauge, calls for 11 inches of sea rise by 2040.

FIU’s Obeysekara, who worked on the NOAA report and helped set the South Florida standards, said this may mean that local governments have planned for more sea rise than we’ll actually see during that period — but that’s a good thing.

“If we have used a higher scenario for our planning up to now, now that curves are a little bit lower maybe we have more resilience,” he said. “If we are more resilient overall, there’s no harm.”

This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative formed to cover the impacts of climate change in the state.