Journal Article

Evaluating IPCC Projections of Global Sea‐Level Change From the Pre‐Satellite Era

Hamlington, Benjamin D., Törnqvist, Torbjörn E., Dangendorf, Sönke, Conrad, Clinton P.

2025

Overview

With an acceleration of global sea‐level rise during the satellite altimetry era (since 1993) firmly established, it is now appropriate to examine sea‐level projections made around the onset of this time period. Here we show that the mid‐range projection from the Second Assessment Report of the IPCC (1995/1996) was strikingly close to what transpired over the next 30 years, with the magnitude of sea‐level rise underestimated by only ∼1 cm. Projections of contributions from individual components were more variable, with a notable underestimation of dynamic mass loss from ice sheets. Nevertheless—and in view of the comparatively limited process understanding, modeling capabilities, and computational resources available three decades ago—these early attempts should inspire confidence in presently available global sea‐level projections. Such multidecadal evaluations of past climate projections, as presented here for sea‐level change, offer useful tests of past climate forecasts, and highlight the essential importance of continued climate monitoring. Plain Language Summary The ultimate test of climate projections occurs by means of subsequent observations. Three decades of satellite‐based measurements of global sea‐level change now enable such a comparison and show that early IPCC climate projections were remarkably accurate. Predictions of glacier mass loss and thermal expansion of seawater were comparatively successful, but the ice‐sheet contributions were underestimated. Nevertheless, these findings provide confidence in model‐based climate projections. Key Points IPCC projections in the mid‐1990s of global sea‐level change over the next 30 years were remarkably robust The largest disparities between projections and observations were due to underestimated dynamic mass loss of ice sheets Comparison of past projections with subsequent observations gives confidence in future climate projections

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Altimetry / Climate change / Climate monitoring / climate projections / Evaluation / Ice sheets / Intergovernmental Panel on Climate Change / Satellite altimetry / Sea level / sea‐level change / Time series