Why sea level isn’t actually level

July 30, 2025

Sea level may sound like a flat, global average—but it’s anything but uniform. Regional differences in ocean currents, land movement, gravity, and atmospheric conditions all affect local sea levels. In Australia, sea-level rise is happening faster in the north and southeast than in other regions.

Since 1900, global mean sea level has risen by more than 22 cm—half of that since 1970. This upward trend is expected to continue for decades, even with deep cuts to emissions, for Australia, where most people live near the coast, understanding where and how sea-level rise is happening is essential for informed decision-making.

This explainer outlines how sea-level changes are measured, why the rise varies across regions, and what it means for planners and coastal communities.