In the next 30 years, sea levels along U.S. coastlines are projected to rise by the same amount they did in the last 100 years, a government report released Tuesday warns. Louisiana is projected to see the worst of it given that the state’s coastal land is sinking as waters rise. 

The updated projections come from the National Oceanic and Atmospheric Association’s 2022 Sea Level Rise Technical Report. The 111-page report warns that coastal infrastructure, communities and ecosystems will face significant consequences over the next 30 years and beyond from rising waters. 

“A little more than a foot of sea level rise might not sound like a lot, but small sea level changes are capable of causing substantial damage to a coastline that is unprepared for them,” said Daniel Gilford, a climate scientist at Climate Central. “Twelve more inches of water is often enough to endanger existing coastal infrastructure, and may require big adaptations.”

By mid century, “typically damaging” flooding is expected to occur on average more than 10 times as often as it does today, the report says. 

The last report released in 2017 had slightly higher projections for sea level rise in the U.S. But the new numbers still paint a grim picture for the country, especially the Gulf Coast, in coming decades. 

“The new numbers have been dialed down a little bit. That doesn’t change the scenario that Louisiana is probably the most vulnerable state in the nation to climate change,” said Louisiana State Climatologist Berry Keim. “Not only is global sea level going up, but our land is going down.”

Louisiana is in a uniquely bad position. Man-made levees along the Mississippi prevent the river from replenishing its sediment deposits, leading to land loss known as subsidence. This already gives the state a higher relative sea level rise than the rest of the country. 

Grand Isle is projected to see 2 feet of sea level rise by 2050. Half of that is due to land loss, the other because of rising seas.

“For Louisiana, the stakes are immense,” Gilford said. “Not including areas protected by levees, more than 46,000 people live on land within 2 feet of the high tide line, and those 2 feet of additional water threaten more than 23,000 Louisiana homes with an estimated value exceeding $2 billion. And under-resourced communities inevitably bear a disproportionate share of the risks.”

Higher seas will make Louisiana’s coast more vulnerable to high-tide flooding, sometimes called “Sunny day flooding,” and make the state more vulnerable to higher storm surges from hurricanes. 

“We’re the front lines,” said Vincent Brown, assistant professor of research focused on weather and climate. “In every single scenario, if you look at the highest water mark, it’s us.” 

Southeastern Louisiana, including New Orleans, is especially more vulnerable to hurricane storm surge as sea levels rise, Brown said. 

Sea level rise will vary regionally along U.S. coasts because of differences in land and ocean height as well as other local factors. The Gulf Coast is projected to see 14-18 inches of sea level rise by mid century, with Louisiana and Texas seeing the worst of it. 

Since the industrial revolution, the burning of fossil fuels – primarily carbon dioxide – has led to global warming via the greenhouse effect. Increases in temperature leads to sea level rise in two ways. 

Warmer water expands and the melting of ice sheets and glaciers add more water to oceans, Keim explained. 

Since the effects of global warming lag, the report says, the changes in the coming decades are the product of warming that’s already happened. In other words, if humans stopped burning fossil fuels today, the projections would still hold. 

Burning greenhouse gasses, Brown explained, is like setting off a freight train. Even if we stop it now, the train will slowly ease to a stop along its track. 

“We are in essence paying right now for warming we’ve generated in the past,” he said. “What’s happening now is just a taste of probably what will happen in the future, given what we’ve been doing the last 20 or 30 years.”

How quickly economies transition away from burning fossil fuels will impact longer term sea level rise scenarios. About 2 feet of sea level rise along U.S. coasts is “increasingly likely” between 2020 and 2100 because of current emissions. 

“Failing to curb future emissions could cause an additional 1.5 – 5 feet of rise for a total of 3.5 – 7 feet by the end of this century,” the report warns.

Louisiana is one of the few Southern states to have a climate plan to reduce greenhouse gas emissions. Louisiana Gov. John Bel Edwards’ wants to reduce the state’s emissions to net zero by mid century will require a dramatic shift to renewable energy like wind and solar away from oil and gas, which the state’s economy has historically depended on.