Sea level rise during past 40 years determined from satellite and in situ observations

The 3.2 +/- 0.2 millimeter per year global mean sea level rise observed by the Topex/Poseidon satellite over 1993-98 is fully explained by thermal exp ansion of the oceans. For the period 1955-96, sea level rise derived from t ide gauge data agrees well with thermal expansion computed at the same loca tions. However, we find that subsampling the thermosteric sea level at usua l tide gauge positions leads to a thermosteric sea level rise twice as larg e as the "true" global mean. As a possible consequence, the 20th century se a level rise estimated from tide gauge records may have been overestimated.