from CO2 Science: The authors write that “satellite altimetry measurements since 1993 have provided unique information about changes in global and regional mean sea levels,” suggesting a mean rate of rise of 3.2 mm/yr for global sea level over the period 1993-2012 (Boening et al., 2012; Cazenave et al., 2012), which “notably exceeds the estimate of 1.8 mm/yr sea level rise for the 20th century (Bindoff et al., 2007).”
So which rate is closest to the truth?
What was done
In a study designed to answer this question, Jevrejeva et al. (2014) say they “renew the global sea level [GSL] reconstruction by Jevrejeva et al. (2006), using monthly mean sea level data collected by the Permanent Service for Mean Sea Level (PSMSL) covering the observations from 1807 to 2010,” thereby improving the GSL reconstruction by increasing data coverage “by using many more stations, particularly in the polar regions, and recently processed historic data series from isolated island stations,” as well as by extending the end of the reconstruction from 2002 to 2009.
What was learned
Quoting the five researchers, “the new reconstruction suggests a linear trend of 1.9 ± 0.3 mm/yr [7.5 inches per century] during the 20th century” and “1.8 ± 0.5 mm/yr [7 inches per century] for the period 1970-2008.”
What it means
Although some regions have recently experienced much greater rates of sea level rise, such as the Arctic (3.6 mm/yr) and Antarctic (4.1 mm/yr), with the mid-1980s even exhibiting a rate of 5.3 mm/yr (Holgate, 2007), this newest analysis of the most comprehensive data set available suggests that there has been no dramatic increase – or any increase, for that matter – in the mean rate of global sea level rise due to the historical increase in the atmosphere’s CO2 concentration.[Therefore, there is no evidence of any human influence on sea levels]
Trends and acceleration in global and regional sea levels since 1807. Global and Planetary Change 113: 11-22. Jevrejeva, S., Moore, J.C., Grinsted, A., Matthews, A.P. and Spada, G. 2014.
We use 1277 tide gauge records since 1807 to provide an improved global sea level reconstruction and analyse the evolution of sea level trend and acceleration. In particular we use new data from the polar regions and remote islands to improve data coverage and extend the reconstruction to 2009. There is a good agreement between the rate of sea level rise (3.2 ± 0.4 mm·yr− 1) calculated from satellite altimetry and the rate of 3.1 ± 0.6 mm·yr− 1 from tide gauge based reconstruction for the overlapping time period (1993–2009). The new reconstruction suggests a linear trend of 1.9 ± 0.3 mm·yr− 1 during the 20th century, with 1.8 ± 0.5 mm·yr− 1 since 1970. Regional linear trends for 14 ocean basins since 1970 show the fastest sea level rise for the Antarctica (4.1 ± 0.8 mm·yr− 1) and Arctic (3.6 ± 0.3 mm·yr− 1). Choice of GIA correction is critical in the trends for the local and regional sea levels, introducing up to 8 mm·yr− 1 uncertainties for individual tide gauge records, up to 2 mm·yr− 1 for regional curves and up to 0.3–0.6 mm·yr− 1 in global sea level reconstruction. We calculate an acceleration of 0.02 ± 0.01 mm·yr− 2 in global sea level (1807–2009). In comparison the steric component of sea level shows an acceleration of 0.006 mm·yr− 2 and mass loss of glaciers accelerates at 0.003 mm·yr− 2 over 200 year long time series.
Full paper with figures is available here: http://www.sciencedirect.com/science/article/pii/S0921818113002750#f0015