Predictions of global and regional sea-level rise using AOGCMs with and without flux adjustment

Abstract

Future global and regional sea-level changes have been calculated using two versions (HadCM2 and HadCM3) of the Hadley Centre coupled atmosphere-ocean general circulation model forced by the IS92a scenario for emissions of greenhouse gases. HadCM3 is a newly developed model which does not require flux adjustment to maintain a stable climatology. Global-average sea-level rise from 1990 to 2100 is predicted to be 0.48 m in HadCM2 and 0.44 m in HadCM3, 60% resulting from thermal expansion of sea-water and the rest from loss of mass of glaciers and small ice-caps. Sea-level rise is smaller in HadCM3 principally because the radiative forcing is slightly less, giving reduced ocean heat uptake and thermal expansion. However, the heat penetrates less deeply in HadCM3; consequently the surface warming is nearly the same. There is marked geographical variation of sea-level change, which is generally similar in the two models; local values range between zero and twice the global average.