Figure 5.A.2. (a) Number of tide gauge stations in the Northern Hemisphere (NH) and Southern Hemisphere (SH) used to derive the global sea level curve (red and blue curves in Figure 5.13) as a function of time. Lower panels show the spatial distribution of tide gauge stations (denoted by red dots) for the periods (b) 1900 to 1909, (c) 1950 to 1959 and (d) 1980 to 1989.