Sea levels along the coastal United States will rise by about a foot or more on average by 2050, government scientists said Tuesday, with the result that rising water now considered “nuisance flooding” will become far more damaging.
A report by researchers from the National Oceanic and Atmospheric Administration and other agencies also found that, at the current rate of warming, at least two feet of sea-level rise is expected by the end of the century.
“What we’re reporting out is historic,” said Richard Spinrad, the NOAA administrator, at a news conference announcing the findings. “The United States is expected to experience as much sea level rise in the next 30 years as we saw over the span of the last century.”
Mr. Spinrad said that while cutting greenhouse gas emissions to limit warming was critically important, the projected sea level rise by 2050 “will happen no matter what we do about emissions.”
The report is an update of a 2017 study, but includes far more precise estimates of sea level rise by 2050, a result of improved computer modeling and better scientific understanding of the impact of global warming on the Greenland and Antarctic ice sheets. That is “providing more confidence in our ability to predict” effects by midcentury, said William Sweet, an oceanographer with NOAA’s National Ocean Service.
About 40 percent of the United States population, or about 130 million people, live within 60 miles of the ocean. But sea level rise will not affect all of them equally, because it is not uniform.
In the United States, land subsidence and compaction of sediments along much of the East and Gulf coasts add to the increase; in those areas sea level rise may exceed one foot in the next three decades, the report said.
On the West Coast, subsidence and compaction are less common, so sea level rise is expected to be at the lower end of projections.
For communities on the East and Gulf coasts, the expected sea level rise “will create a profound increase in the frequency of coastal flooding, even in the absence of storms or heavy rainfall,” said Nicole LeBoeuf, director of the National Ocean Service.
Currently many communities on those coasts experience regular “nuisance” or “sunny day” flooding, when high tides become even higher because of the influence of the moon or other factors. That will change, Dr. Sweet said.
“We definitely are predicting a flood regime shift,” he said.
