Aug. 19, 2022

Thirty years ago, scientists and engineers launched a new satellite to study the rising and falling of seas over time, a task that once could only be done from the coast. TOPEX/Poseidon rocketed into space on August 10, 1992, and started a 30-year record of ocean surface height around the world. The observations have confirmed on a global scale what scientists previously saw from the shoreline: the seas are rising, and the pace is quickening.

Scientists have found that global mean sea level—shown in the line plot above and below—has risen 10.1 centimeters (3.98 inches) since 1993. Over the past 140 years, satellites and tide gauges together show that global sea level has risen 21 to 24 centimeters (8 to 9 inches). That's like covering the contiguous U.S. in about 16 feet (about 5 meters) of water. Recent rates have been unprecedented over the past 2,500-plus years.

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Key Indicators: Global Mean Sea Level