Reanalysis of historical data reveals steeper modern sea-level rise

BBC : Global mean sea-level (GMSL) rise over the past 20 years may actually be greater than previously estimated, according to a recent study published in Nature. The reason is that earlier estimates of GMSL rise between 1900 and 1990 may have been overstated, according to Carling Hay of Harvard University and his colleagues. Data from the earlier time period tend to be sparse, biased toward the midlatitudes in the Northern Hemisphere, and sometimes contaminated by local effects, such as tectonic movements that cause the local land to rise upward or groundwater extraction that causes the land to sink. Better data from satellites and modern tide gauges show that “the acceleration into the last two decades is far worse than previously thought,” says Hay. The researchers hope their findings will prompt the scientific community to revisit future sea-level predictions. In addition, a more accurate understanding of the historical change can help researchers test their climate models by allowing them to perform “hindcasts” to determine how closely the output matches the known data.