Satellite altimetry-based sea level rise over the past 20 years
21-Aug-2019 UT
Sea-level rise is one of the most threatening consequences of ongoing global warming and is a major indicator of climate change . Since the early 1990s global mean sea level (GMSL) trends have been routinely measured with quasi-global coverage and a few days/weeks revisit time by altimeter satellites (ERS,ENVISAT,CRYOSAT,Topex/Poseidon,Jason and SARAL/AltiKa ) showing a significant , of about 30%, slowdown of the mean rate in the last decade -compared to the 1990s-, in coincidence with a plateau in Earth's mean surface temperature evolution. In their analysis of the satellite altimetry-based sea level data for the past 20 years, Scientists separate inter annual natural variability in sea level mostly due to exchange of water between oceans, atmosphere and continents, from the longer-term change probably related to anthropogenic global warming.

They quantitatively estimate these inter annual water mass contributions ,which is mainly, but not exclusively, due to the El Nino-Southern Oscillation (ENSO), using two different approaches: estimate inter annual land water storage plus atmospheric water vapour contributions; or directly estimate the inter annual variability in global ocean mass from GRACE space gravimetry data.

Finally they show that removing from the GMSL time series the inter annual variability contribution (mainly ENSO-related , with a smaller contribution from thermal expansion) , there is no significant rate difference between the 1990s and the 2000s: the GMSL has almost linearly increased during the past 20 years.

Their conclusion confirms the importance to removing from the climate records the short-term natural climate variability in order to extract the global warming signal and clearly advocates for no recent slowdown in global warming.

The research has been supported by CNES, CNRS, MeteoFrance, The University of Toulon and the ESA CCI project.The related paper "The rate of sea-level rise" authored by Anny Cazenave, Habib-Boubacar Dieng, Benoit Meyssignac,Karina von Schuckmann, Bertrand Decharme and Etienne Berthier has has been published online on the Nature Climate Change Letter in March 2014 DOI:10.1038/NCLIMATE2159.