Greenhouse warming and changes in sea level

Abstract

It is likely that the anticipated warming due to the effect of increasing concentration of carbon dioxide and other greenhouse gases will lead to a further and faster rise in world mean sea level. There are many processes in the climate system controlling sea level, but the most important factors in this connection are; thermal expansion of ocean water, retreat of mountain glaciers and small ice caps, changes in the net accumulation of snow over the polar ice. sheets (Greenland, Antarctica), and possible disintegration of the West Antarctic Ice Sheet. A re-evaluation of the various contributions, based on some recent calculations and insights presented in the literature, predicts as most likely changes in sea level (relative to the year 1980): 2040: + 27 cm; 2080:+ 46 cm; 2120: + 69 cm. These are global mean values for eustatic sea level. To arrive at local relative sea level, compaction and crustal movements of tectonic and isostatic origin have to be taken into account. Also, the elastic response of the solid earth to a change in the distribution of surface loading (ice and water) may lead to regional differences. As shown by the time evolution of probability density functions for sea level, the uncertainty in the projection grows rapidly with time. The major part of the uncertainty stems from our inadequate knowledge of the reaction of the polar ice sheets to a changing climatic environment.