US sea levels to rise up to a foot in next 30 years, federal government warns

Disruptive coastal floods could happen ten times as often as they do now

US sea levels are predicted to rise up to a foot by 2050 due to the climate crisis, a new report from the federal government has warned.

Scientists from the National Oceanic and Atmosphere Administration (NOAA), the space agency NASA, and other federal bodies said on Tuesday that they expected the ocean to rise 10-12 inches on average over the next 30 years.

In some regions the forecast is even worse: Louisiana and Texas will see rises of between half a meter and two thirds of a meter, while western Florida, Alabama, and Mississippi will see rises of between 0.4 meters and half a meter.

By 2100 the report predicts that global sea levels could rise by as much as seven feet, and by 2150 as much as 13ft, with worst-case scenarios more likely if the planet heats between three and five degrees Celsius.

Disruptive coastal floods could happen ten times as often as they do now, the report says, meaning some coastal areas would see multiple floods each year, instead of one event every two to five years. It names Miami, New York City, and Charleston, South Carolina as cities most likely to be affected.

"This report supports previous studies and confirms what we have long known: Sea levels are continuing to rise at an alarming rate, endangering communities around the world," said NASA head Bill Nelson.

"[The] science is indisputable and urgent action is required to mitigate a climate crisis that is well underway."

Locals navigate a flooded street in downtown Annapolis, Maryland, in October 2021 (Jim Watson/AFP via Getty Images)

President Joe Biden's chief climate adviser Gina McCarthy said: "This new data on sea rise is the latest reconfirmation that our climate crisis – as the President has said – is blinking ‘code red'.

“We must redouble our efforts to cut the greenhouse gases that cause climate change while, at the same time, help our coastal communities become more resilient in the face of rising seas."

NOAA head Rick Spinrad described it as a "global wake-up call", saying the report would help coastal communities prepare for the future.

The multi-agency report forecasts the same increase in sea-level rise over 30 years as has taken place over the last century.

The rise is driven largely by the melting of glaciers and polar ice caps as the world heats up due to greenhouse gases pumped into the atmosphere by human civilisation, as well as the ocean itself expanding in volume as it gets warmer.

The predictions for 2050 are based on extrapolations of recorded sea level trends since 1970, and are likely to happen “regardless of the emissions pathway” that nations set themselves on.

Meanwhile, the longer-term projections could change based on human action and are drawn from computer simulations, studies of melting glaciers and ice sheets, and forecasts from the United Nation's Intergovernmental Panel on Climate Change (IPCC) which released its last assessment in August.

The federal report did push back the timeline of the "extreme" scenario of eight feet of mean global sea level rise by 2100, but said such levels could be reached in the early decades of the 22nd century.

"By 2050... major and moderate high tide flood events [will be] occurring as frequently as moderate and minor high tide flood events occur today," the report says.

"Without additional risk-reduction measures, US coastal infrastructure, communities, and ecosystems will face significant consequences."