A description of the uncertainties in the Global Mean Sea Level (GMSL) record has been performed; 25 years of satellite altimetry data were used to estimate the error variance–covariance matrix for the GMSL record to derive its confidence envelope. Then a least square approach was used to estimate the GMSL trend and acceleration uncertainties over any time periods. A GMSL trend of 3.35 ± 0.4 mm/yr and a GMSL acceleration of 0.12 ± 0.07 mm/yr² have been found within a 90 % confidence level.