We were wrong. Between 1900 and 1990, there was a smaller rise in sea level than had been estimated. This overestimate of 30% means that since 1990, with many earlier emissions and meltings contributing over many decades to the temperature rise, the acceleration in rise has been greater!
The adjustment is in the tide gauge measurement tables from instruments dotted around various coasts in the last century. Because of this non-random distribution, excluding mid-ocean conditions completely, it could not give an accurate figure with global sea-levels supposedly rising from 1.5 to 1.8mm/year. Instead, we now realise the rises were of an order of only 1.2mm/year. The rise since 1990 has therefore become a massive 3.0mm/year, because of accelerating emissions and temperatures. The averaging out (as well as the missing data) that took place with the old estimates was far too inaccurate.
Carling Hay and Eric Morrow of Harvard EPS Department,MA, in the US publicise their study in the Harvard Gazette here, and in the journal, Nature. Half a metre (18inch) rises are now expected for the end of the decade with that acceleration causing all figures to adjust upwards. For example, by the end of the century, a rise of a whole metre is possible. Carling describes the results as
effects due to the last ice age, heating and expansion of the ocean due to global warming, changes in ocean circulation, and present-day melting of land ice, all of which result in unique patterns of sea-level change. These processes combine to produce the observed global mean sea-level rise.
The IPCC (Intergovernmental Panel on Climate Change) have estimated previously that sea-level rises would reach between 61 and 98cm, depending on the emissions we produce before 2100. Now look at the long list of transport problems that will be affected almost immediately (including a neat look at the early tide gauge measurements that were taken a century ago: SEE SLR hotspot.)