Global sea level rise: the past decade vs. the past 100 years

Based on observations from the TOPEX/Poseidon and Jason satellite altimeter missions, it now appears that global sea level rose over the past eleven years at a rate of about 2.5 mm/yr, nearly three times greater than the lower bound of the most recent estimate by the Intergovernmental Panel on Climate Change (IPCC). This result can be interpreted in one of two ways. Either the rate of Global Sea Level Rise (GSLR) underwent a huge acceleration in the 1990's, or the lower bound of the IPCC assessment represents an underestimate. To help resolve this dilemma, we present an analysis of sea level measurements at tide gauges combined with observations of temperature and salinity in the Pacific and Atlantic Oceans close to the gauges. We find that gauge-determined rates of sea level rise, which encompass both mass and volume changes, are two to three times higher than the rates due to volume change derived from temperature and salinity data. This analysis supports earlier studies that put the twentieth-century rate of GSLR close to 2 mm/yr, i.e. the upper bound of the IPCC estimate. Some issues related to the determination of GSLR from multiple satellite altimeter missions will be discussed.