Graph: Measured and projected global sea level rise (credit: NASA/JPL-Caltech)
Last year, global sea level rose faster than expected. The rate of sea level rise in 2024 was 5.9 millimetres per year, much higher than the expected rate of 4.3 millimetres per year, according to a NASA-led analysis. This was due to the extraordinary high temperatures of the oceans in 2024.
In recent years, about a third of sea level rise came from the thermal expansion of seawater. Two-thirds of sea level rise was due to the melting of glaciers and the ice of Greenland and the Antarctic. In 2024, those contributions flipped: Two-thirds of sea level rise was caused by thermal expansion of the unusually warm oceans.
Sea level rise is accelerating. The rate of global sea level rise has increased from 2.1 mm per year in 1993 to 4.5 mm per year in 2023, the time series of satellite data shows. The rate of sea level rise is increasing by an additional 1 mm every ten years. The ‘jump’ of 4.5 to 5.9 millimetres of sea level rise in 2023 and 2024, respectively, is an extraordinary situation and not a trend. In 2025, sea level rise will probably drop below 5 millimetres per year again.
However, it will take only a few years before the trend is exceeding the 5 millimetres per year sea level rise. This value has a special meaning: Studies have shown that deltas and low-lying coastal zones may start to drown once sea level rise enters a critical range of 5-10 mm per year. With an acceleration of sea level rise by 1 mm every ten years, we are about to enter this uncharted territory.
Sources:
- Veng, T. en O. B. Andersen, 2020. Consolidating sea level acceleration estimates from satellite altimetry. Advances in Space Research 68 (2): 496-503.
- Hamlington, B.D. et al., 2024. The rate of global sea level rise doubled during the past three decades. Communications Earth & Environment 5, 601.
- https://www.jpl.nasa.gov
