There are many factors affecting mean sea level, and local mean sea level. In general mean sea level is measuring still water, when there is no tide or anything. Imagine 2mm sea level increase, and count the area of ocean, and see the volume of water increased. Since there are tides every day, the water raise in this case is not gonna be 2mm. In California, the frequency of high wave, greater than 16 ft or 20 ft has significantly increased, especially during El Nino season. That means more flooding, cliff and bluff erosion along the coastline.