Statistical analysis of recent Mediterranean Sea-level data

The Global rate of sea level rise during the 20th century is generally agreed to be 1-2.5 mm/year. An examination of the four sea-level data series available for the Mediterranean shows a sea-level rise of a similar rate. A statistical analysis based on linear regression reveals this trend to be inconsistent over the century. The four time-series were divided into two different sets: the first consists of records prior to 1960, when sea level was rising consistently, and the second from 1961 and onward, when there was no significant sea-level trend. Dividing these two data sets into shorter time periods, by using additional data from 41 tide-gauging stations in the Mediterranean, showed a consistent trend prior to 1960. Between 1961 and 1989 the records show no significant trend. This can be due to a rise in mean surface atmospheric pressure of 1.74-3.31 hpa during that period, rather than an eustatic decrease in the rate of sea-level rise. From 1990 onward the sea level recorded in most Mediterranean tide gauges indicates a rise in sea level at a rate 5-10 times higher than the 20th century mean rate. While this trend should be regarded with some caution because of the relatively short data series, the trend observed coincides with the increase in global land and marine surface temperatures during the 1990s, and it is important to note that no other short sub-period in the data sets shows such an extreme trend.