The Global Sea Level Observing System (GLOSS) uses a network of 290 sea level stations located around the world to measure global sea levels. GLOSS has been used to collect real-time measurements of sea levels since the 2004 Indian Ocean tsunami, and this information is used to support long-term climate change studies.
GLOSS measures global sea levels as part of the IOC's Global Ocean Observing System (GOOS). Measurements are conducted under the auspices of the Joint Centre for Oceanographic and Marine Meteorological Observing Programme Support (JCOMMOPS) of the Intergovernmental Oceanographic Commission (IOC) and the World Meteorological Organisation (WMO).
GLOSS website: http://www.gloss-sealevel.org