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Global Mean Sea Level

The average height of the world ocean, measured from space since 1993.

Global mean sea level since 1993

Satellite sea level observations. Credit: NASA
Rise since 1993
…mm
Rate now
…mm/yr
Acceleration
…mm/yr²
Monthly meanUncertainty12 month running meanQuadratic fit
Monthly means of NASA's roughly 10 day global mean sea level series, with the seasonal cycle retained. Uncertainty is NASA's stated value for each measurement.

Key takeaways

  • Global mean sea level is about … mm (… inches) higher than in 1993.
  • The rise is accelerating. The rate has grown from about … mm per year in 1993 to about … mm per year today.
  • Year to year wiggles come mostly from El Niño and La Niña, which shift water between ocean and land.

What is global mean sea level?

Global mean sea level is the average height of the entire ocean surface. Because it averages over the whole ocean, it filters out tides, waves and most local effects, leaving the signal of water being added to the ocean and of the ocean expanding as it warms.

What are we looking at?

Since late 1992 a series of radar altimeter satellites has measured the height of the sea surface along the same ground track every ten days: TOPEX/Poseidon, Jason-1, OSTM/Jason-2, Jason-3 and now Sentinel-6 Michael Freilich. Careful cross calibration during overlap periods stitches these missions into one continuous record. The chart shows the change relative to the start of 1993.

The seasonal cycle is still in the data, so sea level peaks each northern autumn. The dashed line removes that cycle with a 12 month running mean. The dotted line is a quadratic fit, whose steadily increasing slope is the acceleration of sea level rise.

Why does it go up and down?

During La Niña, heavy rain falls over land, especially over South America and Australia, temporarily lowering the ocean. During El Niño, that water returns to the sea and heat is released from the tropical Pacific, so sea level jumps. In 2025 La Niña held the yearly rise to under 1 mm. The rise through 2026 shows the ocean catching back up as conditions in the Pacific turn toward El Niño.

Why do we care?

Each millimeter of global rise is spread over 360 million square kilometers of ocean. Along coasts, a higher baseline means tides and storm surges reach farther inland and more often. Global mean sea level is the single best measure of how much the climate system has changed the ocean, and it sets the starting point for every local projection.

Data: NASA global mean sea level indicator, distributed through NASA Earth Indicators and PO.DAAC. Reference: Hamlington, B.D. et al. (2024), The rate of global sea level rise doubled during the past three decades, Communications Earth & Environment, doi:10.1038/s43247-024-01761-5.