Observations of sea level from coastal tide gauges indicates that global sea level has been rising at a rate of between 1 and 2 mm/yr during the 20th century. This is substantially faster than estimates of global sea-level rise of 0.5 mm/yr over the last 6000 years and 0.1-0.2 mm/yr over the last 3000 years. There is no discernible acceleration in the rate of sea-level rise during the 20th century.For the 21st century, models indicate that ocean thermal expansion will be the largest contributor to sea-level rise. The melting of glaciers and ice -caps also contributes to sea-level rise. For Greenland, increased ablation is estimated to be somewhat larger than increased precipitation. For Antarctica, increased accumulation is estimated topartially offset a rise in sea level from other sources. There will be a continuingcontribution to sea-level rise as a result of the response of the ice sheets to changes in climate since the Last Glacial Maximum. Changes in terrestrial storage is estimated to have partially offset sea-level rise from other sources. Combining estimates of each of these components results in a calculated rate of sea-level rise during the 20 thcentury which ranges from about zero to about 2 mm/yr, and with little computed acceleration over the period.Sea-level rise projections for 2100 are several tens of centimetres above 1990 levels. For the early decades of the 21st century, the range of projections is dominated by modelling uncertainties. For longer lead times, uncertainties in greenhouse gas emissions also contribute significantly to the range in sea -level projections. Beyond 2100, sea level will continue to rise for centuries after greenhouse gas concentrations have stabilised. After 500 years, sea-level rise from thermal expansion may onlyhave reached half of its eventual level. Ice sheets will continue to react to climate change during the next thousand years even if the warming is stabilised.