Study: Global sea level rise has decelerated since 1950s – The 1958-2014 Sea Level Rise is Neither Unusual Or Unprecedented

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by Kenneth Richard / Today, 05:38

Antarctica & Greenland CombinedAdded

0.59 Of An Inch To Sea Levels Since 1958

Graph Source: Grinsted et al., 2009

In a newly published paper, oceanographers estimate that global sea levels rose at a rate of ~1.42 mm per year⁻¹ (1.32 to 1.52 mm/yr⁻¹) between 1958 and 2014, a 56-year span that directly coincides with an unprecedented rise in anthropogenic CO2 emissions.

Frederiske et al.,2018

“For the first time, it is shown that for most basins the reconstructed sea level trend and acceleration can be explained by the sum of contributors, as well as a large part of the decadal variability. The global-mean sea level reconstruction shows a trend of 1.5 ± 0.2 mm yr⁻¹ over 1958–2014 (1σ), compared to 1.3 ± 0.1 mm yr⁻¹ for the sum of contributors.”

This rate (which scores between the estimated sum of sea level rise contributors and a reconstruction from tide gauge and satellite measurements) is similar to the reconstructed rate for 1954-2003 (1.45 mm/yr⁻¹) estimated by Dr. Simon Holgate (2007).

Holgate, 2007

“The rate of sea level change was found to be larger in the early part of last century (2.03 ± 0.35 mm/yr 1904–1953), in comparison with the latter part (1.45 ± 0.34mm/yr 1954–2003).”

Extrapolating the annual rate of rise over the 56-year period (1958-2014), global sea levels rose 7.95 centimeters (cm) in total, or 3.13 inches during the Anthropogenic Global Warming (AGW) era.

Negligible Polar Ice Sheet Melt Contribution To Sea Level Rise Since 1958

Of those 7.95 cm, just 1.17 cm (0.46 of an inch) of meltwater was contributed by Greenland Ice Sheet in 56 years, and the Antarctic ice sheet contributed just 0.37 of a cm (0.13 of an inch).

1958-2014 Sea Level Rise Neither Unusual Or Unprecedented

If 3.1 inches of sea level rise over a 56-year span does not appear to be either alarming or unprecedented, perhaps it’s because they are indeed neither — especially when one considers longer-term contexts.

As Holgate (2007) summarizes above, the ~50-year global rate of sea level rise was substantially higher (2.03 mm/yr⁻¹⁾ during the first half of the 20th century (1904-1953) compared to the post-1950s period (1.45 mm/yr⁻¹ 1954-2003).

In other words, since the 1950s, global sea level rise has decelerated.

The 1920 to 1950 period had rates of rise that were either higher or rivaled the rates of the more recent decades (using satellite altimetry modeling [3.4 mm/yr⁻¹ ]). In fact, when the anomalous decadal variability is removed, the fastest rates of sea level rise occurred during the 1920 to 1950 period.