Thursday, February 13, 2014

New paper finds 20th century sea level rise was only 4.3 inches in S Hemisphere, 7.9 inches N Hemisphere

A paper published today in Geophysical Research Letters "challenges the widely accepted value of global sea level rise for the 20th century" and finds sea levels rose in the southern hemisphere at only about half the rate of the northern hemisphere. According to the authors, sea levels rose [relative to land] only 7.9 inches in the northern hemisphere and 4.3 inches over the entire 20th century.

This implies relative sea level change is primarily a localized phenomenon related to subsidence or post-glacial rebound [land height changes] rather than melting ice or steric sea level changes [thermal expansion from warming]. 

Evidence for a differential sea level rise between hemispheres over the 20th century

Guy Wöppelmann1,*, Marta Marcos2, Alvaro Santamaría-Gómez1,3, Belén Martín-Míguez4,
Marie-Noëlle Bouin5, Médéric Gravelle1

Tide gauge records are the primary source of sea level information over multi-decadal to century timescales. A critical issue in using this type of data to determine global climate-related contributions to sea level change concerns the vertical motion of the land upon which the gauges are grounded. Here we use observations from the Global Positioning System for the correction of this vertical land motion. As a result, the spatial coherence in the rates of sea level change during the 20th century is highlighted at the local and the regional scales, ultimately revealing a clearly distinct behavior between the northern and the southern hemispheres with values of 2.0 mm/year and 1.1 mm/year, respectively. Our findings challenge the widely accepted value of global sea level rise for the 20th century.

1 comment:

  1. Considering that the IPCC (2013) states that SLR was 1.7 mm/yr for 1901-2010, or 6.6 inches per century, the combined mean value for both hemispheres implied here, 1.55 mm/yr, or 6.1 inches per century, isn't demonstrably different. The higher value (6.6 inches) through 2010 undoubtedly included the alleged 3+mm/yr value found by some scientists to have occurred from 1993 to 2009 (though others have SLR decelerating since the early 2000s).

    “It is very likely that the global mean rate was 1.7 [1.5 to 1.9] mm yr–1 between 1901 and 2010 for a total sea level rise of 0.19 [0.17 to 0.21] m." ---IPCC AR5