Though global sea levels "varied little" for the 2,000 years before the 20th century, [1]CNN reports that sea levels then "started rising and have not stopped since — and the pace is accelerating."

And sea level rise "was unexpectedly high last year, according to a recent NASA [2]analysis of satellite data."

> More concerning, however, is the longer-term trend. The rate of annual sea level rise has more than doubled over the past 30 years, resulting in the global sea level [3]increasing 4 inches since 1993. "It's like we're putting our foot on the gas pedal," said Benjamin Hamlington, a research scientist in the Sea Level and Ice Group at NASA's Jet Propulsion Laboratory. While other climate signals fluctuate, global sea level has a "persistent rise," he told CNN.

>

> It spells trouble for the future. Scientists have a good idea how much average sea level will rise by 2050 — around [4]6 inches globally, and as much as [5]10 to 12 inches in the US. Past 2050, however, things get very fuzzy. "We have such a huge range of uncertainty," said Dirk Notz, head of sea ice at the University of Hamburg. "The numbers are just getting higher and higher and higher very quickly." The world could easily see an extra 3 feet of sea level rise by 2100, he told CNN; it could also take hundreds of years to reach that level. Scientists simply don't know enough yet to project what will happen.

>

> What scientists are crystal clear about is the reason for the rise: human-caused global warming. Oceans absorb roughly 90% of the excess heat primarily produced by burning fossil fuels, and as water heats up it expands. Heat in the oceans and atmosphere is also driving [6]melting of the Greenland and [7]Antarctic ice sheets , which together hold enough fresh water to raise global sea levels by around 213 feet. Melting ice sheets have driven [8]roughly two-thirds of longer-term sea level rise, although last year — the planet's hottest on record — the two factors flipped, making ocean warming the main driver. [SciTechDaily reports that between 2021 and 2023 the Antarctica ice sheet actually showed an overall increase in mass which exerted [9]a negative contribution to sea level rise .]

>

> It's likely that an increase of about 3 feet is already locked in, Notz said, because "we have pushed the system too hard." The big question is, how quickly will it happen? Ice sheets are the biggest uncertainty, as it's not clear how fast they'll react as the world heats up — whether they'll melt steadily or reach a tipping point and rapidly collapse... [I]t's still unclear how processes may unfold over the next decades and centuries. Antarctica is "the elephant in the room," he said. [10]Alarming changes are unfolding on this vast icy continent, which holds enough water to raise levels by 190 feet.

>

> Notz describes the ice sheet as an "awakening giant:" It takes a long time to wake up but once awake, "it's very, very difficult to put it back to sleep."

The article notes that U.S. coastlines "are tracking above global average and toward the upper end of climate model projections, NASA's Hamlington said." (The state of Louisiana [11]has one of the highest rates of land loss in the world , with some places experiencing nearly 4x the global rate of relative sea level rise.) But it's not just a problem for America.

"Over the next three decades, islands such as Tuvalu, Kiribati and Fiji will experience at least 6 inches of sea level rise even if the world reduces planet-heating pollution, according to NASA....

> "Entire villages in Fiji have been formally relocated," said Fijian activist George Nacewa, from climate group 350.org, "the incoming tides are flooding our roads and inundating our crops." However, if the pace accelerates rapidly, "it will be very, very difficult to adapt to, because things unfold too quickly," he said.

"Humans still have control over how fast sea level rises over the next decades and centuries by cutting emissions, Notz noted."

Thanks to long-time Slashdot reader [12]RoccamOccam for sharing the news.



[1] https://www.cnn.com/2025/05/09/climate/sea-level-rise-melting-ice-sheets

[2] https://www.nasa.gov/missions/jason-cs-sentinel-6/sentinel-6-michael-freilich/nasa-analysis-shows-unexpected-amount-of-sea-level-rise-in-2024/

[3] https://www.nasa.gov/missions/jason-cs-sentinel-6/sentinel-6-michael-freilich/nasa-analysis-shows-unexpected-amount-of-sea-level-rise-in-2024/

[4] https://earth.gov/sealevel/sea-level-explorer/?type=global&scope=section_1

[5] https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level

[6] https://www.cnn.com/2025/03/12/climate/arctic-sea-ice-heat-downward-spiral

[7] https://www.cnn.com/2024/05/20/climate/doomsday-glacier-melt-antarctica-climate-intl

[8] https://earth.gov/sealevel/us/sea-level-101/global-sea-level-rise/the-basics/

[9] https://scitechdaily.com/antarcticas-astonishing-rebound-ice-sheet-grows-for-the-first-time-in-decades/

[10] https://www.cnn.com/2023/02/21/world/antarctic-sea-ice-record-low-climate-intl

[11] https://www.epa.gov/climateimpacts/climate-change-connections-louisiana-mississippi-river-delta

[12] https://www.slashdot.org/~RoccamOccam