Ocean

Sea Level

Key message

Global mean sea level reached observed record levels in 2026

Explanation

Global mean sea level has been measured by satellites since 1993 using altimeters that record the time it takes for a radar signal to reach the sea-surface and return to the satellite. The rate of sea level has increased since 1993 due to increased melt from glaciers and ice sheets as well as expansion of the warming upper ocean waters.

Data source

Legeais, J.-F., Ablain, M., Zawadzki, L., Zuo, H., Johannessen, J. A., Scharffenberg, M. G., Fenoglio-Marc, L., Fernandes, M. J., Andersen, O. B., Rudenko, S., Cipollini, P., Quartly, G. D., Passaro, M., Cazenave, A., and Benveniste, J. (2018). An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative. Earth System Science Data, 10, 281-301. DOI: 10.5194/essd-10-281-2018.

Related resources

Methodology

This indicator is based on satellite altimetry measurements, which provides the height of the sea surface with respect to a reference surface (typically a reference ellipsoid). The data have been adjusted to account for a number of factors, including how the atmosphere affects radar signals, the state of the ocean surface, tides and the continuing long-term rebound of the solid Earth following the last ice age, and the responses of the ocean to the atmosphere.

 

An instrumental drift of the TOPEX-A radar, one of the first satellite altimeters used in the series covering the period 1993–1998, has been corrected using an empirical correction applied consistently to all datasets.

 

The data have been de-seasonalized. Anomalies were calculated relative to a 1999-2025 baseline for each dataset, which is period common to all four datasets.