Global Sea Level Projections to 2100 Using Methodology of the Intergovernmental Panel on Climate Change

Forecasts of sea-level rise by 2100 have such a wide range that objective planning is difficult. In 2007, the Intergovernmental Panel on Climate Change (IPCC) forecast a sea-level rise from 1990 to 2100 between 0.18 and 0.59 m, but they did not completely consider contributions from Greenland and Antarctica in determining the upper limit. Recent projections by others have been larger, typically 1–2 m, with Greenland and Antarctica being the greatest contributors. However, these projections are usually maximum possible rises without probabilities of occurrence, whereas the maximum IPCC projection is at the 95% confidence level with a 2.5% probability of being equaled or exceeded. Project planning and design generally require projections with associated probabilities to determine risk. This paper shows what worldwide tide gauge data tell us about sea-level rise trends and accelerations in the twentieth century, and satellite altimeter recordings tell us about the rise since the early 1990s. Using IPCC methodology, sea level projections with associated probabilities are made from 1990 to 2100. Projections of Greenland and Antarctica contributions are estimated based on satellite measurements of current ice-mass-loss trends and accelerations, and then they are added to contributions from thermal expansion and melting of glaciers and ice caps based on the latest information. Sea-level rise projections from 1990 to 2100 are 0.18, 0.48, and 0.82 m at 5, 50, and 95% confidence levels, respectively.