production of data set time series of variables that describe the state of the atmosphere, land, ocean and the cryosphere. Sea ice is listed as one of the 13 Essential Climate Variables and the aim of [...] group is to produce datasets of sea ice concentration sea ice thickness sea ice drift that include Arctic and Antarctic sea ice and the respective uncertainties. The data sets both parameters will consist [...] thickness time series from data of the ERS-1, ERS-2, EnviSat and CryoSat-2 radar altimeter missions of Arctic and Antarctic sea ice. The production of a time-series of Antarctic sea-ice thickness is based on