"Sea level" refers to the average height of the surface of the ocean around the world. It is used as a baseline to measure the height or altitude of land above or below it. Full definition
Several different components contribute to rising sea levels rise, including water expanding as it warms, melting glaciers and ice sheets, and changes to how much water is stored on land. (carbonbrief.org)
One of these was his claim of sea level rise of up to 20 feet «in the near future». (drtimball.com)
So, 9 ″ from sinking, 3 ″ from local changes and 5 ″ from global sea level change. (wattsupwiththat.com)