Use of DInSAR techniques for the assessment of tide gauge measurements for long term past sea level evolution estimation reliability

Before the satellite altimetry era, tide gauges are the unique source of information to monitor global sea level rise due to anthropogenic climate change. As sea level changes display regional variability, its global mean can be estimated by averaging trends from good quality tide gauge. This leads to sea level rise rates of 1.65 +/− 0.2 mm/yr during the 20th century. However, this value and the related uncertainties are subject to discussion: 1. the network of available tide gauges is distributed in an uneven way: most of datasets available cover the Northern hemisphere, whereas previous studies suggest that sea level rise has been different in the northern and southern hemispheres. 2. over the altimetry era (1992-present), the sea level budget can be estimated by summing each contributing factor (mountain glaciers, ice sheets, thermosteric effects, land water storage), within uncertainties reaching 10 to 15% for each component. The same validation is more difficult for the recent period, because less data are available, thus questioning again the precise rate of mean sea level over the 20th century.