Global sea level record from satellite altimetry: accomplishments and challenges

The trend of sea level change and its geographic pattern present a powerful indicator of the overall extent of climate change as well as pose a long-term threat to the world's heavily populated coastal zones. The global and direct measurement of sea level from satellite altimetry over the past two decades, as a key part of a global observing system, has enabled quantitative determination of sea level change and its relation to natural and human-induced causes. Major results from the data record will be reviewed to highlight the challenges in distinguishing between natural variability and long-term trends from human activities. As long-term climate data records from satellite observations are inevitably to be built from successive missions with progressively changing technologies, a major challenge is concerted effort in cross-calibration to ensure consistency between new measurements with existing records. As the desire of increasing spatial resolution to resolve energetic small-scale variability dictates the development of high-resolution wide-swath altimeter, the need for thoughtful design of a system that is able to demonstrate proper transition of technologies in terms of providing consistent global sea level data record will be discussed.