How we track sea-level rise

What the dashboard shows, where the numbers come from, and what they can’t tell you.

The short answer

The global ocean is about 8 centimetres (3 inches) higher than in 1993, when continuous satellite measurements began. That sounds small, but the rise is speeding up: it now runs at roughly 4 to 5 millimetres a year, about three times the average rate from 1901 to 1990. A faster rise is what turns occasional coastal flooding into routine flooding, so the dashboard leads with the rate rather than the total.

Two things raise the sea: warmer water takes up more space, and melting land ice adds water. For 2006–2018, the IPCC attributes about 39% of the rise to warming water, about 45% to melting glaciers and ice sheets, and the rest to changes in how much water is stored on land.

How we know

From space. Since 1992, a series of satellites (TOPEX/Poseidon, Jason-1, -2 and -3, and now Sentinel-6 Michael Freilich) has flown the same path, timing radar pulses bounced off the sea surface to measure its height. Averaged over the whole ice-free ocean every ten days, this gives global mean sea level. We use the combined record from NOAA’s Laboratory for Satellite Altimetry, counted from 1993.

From the coast. Tide gauges on harbour walls measure sea level relative to the land, which itself can be sinking or rising. Where the ground is sinking, as in Jakarta or parts of the US Gulf Coast, the rise residents experience can be much faster than the satellite average. The dashboard keeps the two apart and says which is which.

From the ice sheets. The ice-loss figures for Greenland and Antarctica come from IMBIE, an international assessment that reconciles satellite measurements of ice height, flow and gravity. Over 1992–2020 Greenland lost about 169 billion tonnes of ice a year and Antarctica about 92, and the loss has sped up: it was roughly three and a half times faster in 2016–2020 than in 1992–1996.

Reading the dashboard

The speed-up. The headline compares the rate of rise in the recent half of the satellite record with the rate in the early half. The same two trend lines are drawn on the chart with their rates, so the headline and the picture show the same calculation.

City figures. The city tiles and 2050 ranges are reference values from published projections, not live calculations for each city.

How current each part is

Satellite sea level: NOAA has not updated this series since February 2025 and it is no longer maintained. We keep the whole record it covers and still check it every night. A maintained satellite record will be added: where the two overlap, it serves as an independent check on this one, and it carries the series forward from 2025.
Ice-sheet loss: IMBIE’s 2023 assessment, covering 1992–2020; updated when the next assessment is published.
What makes the sea rise: IPCC Sixth Assessment Report, 2006–2018.
City trends and projections: reference values, updated by hand.

What the dashboard can’t tell you

It cannot tell you the flood risk at a particular address. That depends on local land movement, the shape of the coast, tides and storms. Global mean sea level is a planetary benchmark, not a street-level forecast.

The satellite record also depends on corrections most readers never see: for the slow rebound of the land since the last ice age, for small differences between one satellite and the next, and for the sinking of the ocean floor. These are handled by the space agencies; the remaining uncertainty is why the rate, not the last millimetre, is the honest headline.

Credits

The sea-level record exists because NASA and the French space agency CNES built and flew TOPEX/Poseidon and the Jason satellites, and NASA, NOAA, the European Space Agency and EUMETSAT now fly Sentinel-6; NOAA’s altimetry team maintains the combined record; the IMBIE community reconciles the ice-sheet numbers; and tide gauges such as the one at The Battery in New York have measured continuously since the 1850s. This dashboard collects and presents their work.

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