Sea level is bumpy, but it rising overall as polar and glacial ice melts. This image shows TOPEX sea level data in Eastern Equatorial Pacific from Dec. 4, 1997, during an El Nino event (visible as high red surface). Image courtesy of NASA/Goddard Space Flight Center Scientific Visualization Studio
Satellite tracking of the oceans and the melting of ice sheets and glaciers from 2005 to 2011 now confirms that the seas worldwide have risen 2.39 millimeters per year over that seven-year period, and hasn’t stopped. That’s almost 17 millimeters over those seven years, or more than 5/8ths of an inch, about the width of a typical adult index finger at the first knuckle.
There is also the matter of those places where the land is also sinking, which is common along the Gulf Coast, for instance. Sinking land increases the effective sea level rise in those places. In New Orleans, for instance, satellite data has shown that different parts of the city are sinking at rates ranging from 1.79 to more than 15 millimeters per year. Tack on another 2.39 millimeters to those numbers to get a general idea of how much sea level is rising relative to the ground under the Big Easy.
Then they factored in changes in the density of the oceans using data from a network of oceans floats. They found that a drop in water density — usually that means warming water — over the same period led to a sea-level rise of about 0.6 millimeters per year. Add that to the the 1.8 mm per year and you have a number that matches a figure calculated by other researchers using totally different data from different satellite sensors.