Global sea levels are rising faster than they were three decades ago, and scientists say warming oceans are now one of the main forces pushing the increase. New climate assessments show that the pace of sea-level rise has doubled since the early 1990s, while ocean warming itself has also accelerated sharply.
According to NASA-supported satellite analysis, the rate of global sea-level rise increased from about 2.1 millimetres per year in 1993 to roughly 4.5 millimetres per year by 2024. Over decades, those small yearly numbers add up. Since satellites began tracking global sea level in the early 1990s, the ocean has risen by more than 10 centimetres overall.
The reason is simple, but deeply worrying: as the planet warms, the ocean absorbs most of the trapped heat. Warmer seawater expands, and that expansion pushes sea levels higher. Melting glaciers and ice sheets also add more water to the ocean, making the problem worse.
UNESCO has warned that the ocean absorbs about 90% of excess heat trapped by greenhouse gases. Its State of the Ocean findings say warming ocean temperatures now account for around 40% of global sea-level rise, while the rate of sea-level rise has doubled over the past 30 years, adding about 9 centimetres in that period.
The World Meteorological Organization’s latest climate assessment adds another worrying signal. It says ocean heat content reached its highest level in the 66-year observational record in 2025, beating the previous record set in 2024. The rate of ocean warming from 2005 to 2025 was more than twice the rate recorded from 1960 to 2005.
This is not just about water creeping up slowly on a chart. Higher seas make coastal flooding more frequent, worsen storm surges, speed up shoreline erosion and push saltwater into freshwater supplies. Low-lying communities, island states and crowded coastal cities are especially exposed.
The danger is also uneven. Some coastlines see sea levels rise faster than the global average because of land sinking, ocean currents or regional wind patterns. That means two cities can face very different risks even when the global trend is the same.
Scientists say the acceleration is a long-term warning. Even if yearly changes look small, the direction is clear: the ocean is getting warmer, expanding faster and placing more pressure on coastal life.
For millions living near the sea, this is no longer a distant climate issue. It is becoming a planning problem, an infrastructure problem and, increasingly, a survival problem.
