Sea level is rising — and speeding up

Two things make water rise: warmer oceans expand, and melting land ice adds volume. Both are accelerating, and together they have lifted the global mean sea surface by about 111 mm (4.4 inches) since 1993.

The rate has doubled

The satellite-era average is about 3.4 mm per year, but the current rate has climbed to roughly 4.5 mm per year — more than double the early-1990s pace. NASA measured an unexpectedly large rise in 2024, driven more by thermal expansion than usual.

Ice is the wild card

• Glaciers lost about 450 billion tonnes in 2024; every one of the world's 19 glacier regions has lost mass for three straight years (WGMS).
• Arctic sea ice shrank to 4.60 million km² in September 2025 and is declining about 12% per decade.
• Antarctic sea ice hit near-record lows for the fourth year running, after an abrupt downturn since 2016.

Sea ice does not raise sea level directly (it already floats), but it is a sensitive gauge of a warming planet and its loss accelerates further warming. The land ice locked in glaciers and the Greenland and Antarctic sheets is what will determine coastlines for centuries.

Why millimetres matter

A few millimetres a year sounds small, but it compounds, and it raises the baseline from which storm surges and high tides operate. Hundreds of millions of people live within a metre or two of present sea level.