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Over the last couple of days at their Die kalte Sonne blog Geologist Dr. Sebastian Lüning and professor of chemistry Fritz Vahrenholt have focused their attention on sea level rise.

On Monday they wrote a piece titled: “Sea level rise lagging behind expectations: Now only ‘data massaging’ helps“.

In their post the two authors present a number of charts and cite many papers. In the end they conclude that sea level rise has not accelerated at all, despite what the media and a few alarmist scientists may otherwise claim.

Lüning and Vahrenholt write that sea level acceleration is the result only when one dubiously fudges the data:

What would you think if a soccer game ended with a score of 3:1, but the result later changed to 3:3?”

Today Lüning and Vahrenholt followed with another post on sea level rise, which shows that the methodology used at times by scientists to compute and project sea level rise leaves little to be desired.

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By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt

[Translated/ edited by P Gosselin]

For over one hundred years there has been a network of coastal tide gauges around the world that serve to measure the sea level. The hard data that is recorded play a decisive role in determining sea level rise. Because some coastal locations are rising and some are sinking, the corresponding vertical movement has to subtracted from or added to the tide gauge readings respectively. Using satellite measurements, today this can be corrected with reasonable accuracy. In March 2014 in a paper in the Geophysical Research Letters a team of scientists led by Guy Wöppelmann conducted a global revision of all GPS corrected coatal tide gauge measurements for the 20th century. The result is interesting: While sea level rose an average of 2.0 mm per year in the northern hemisphere, it was only about half as much in the southern hemisphere: 1.1 mm/year. What follows is the paper’s abstract:

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

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.

The rise in sea level over the past 150 years is foremost attributed to the thermal expansion of the warmed water and the melt water from glaciers and the ice caps. But in November 2014 in the Environmental Research Letters Paul Durack showed that also ocean water salinity also contributed to sea level rise to a non-negligible extent. The Lawrence Livermore National Laboratory reported in a press release :

The team found that there was a long-term (1950-2008) pattern in halosteric (salinity-driven) sea level changes in the global ocean, with sea level increases occurring in the Pacific Ocean and sea level decreases in the Atlantic. These salinity-driven sea level changes have not been thoroughly investigated in previous long-term estimates of sea level change. When the scientists contrasted these results with models, the team found that models also simulated these basin-scale patterns, and that the magnitude of these changes was surprisingly large, making up about 25 percent of the total sea level change. ‘By contrasting two long-term estimates of sea level change to simulations provided from a large suite of climate model simulations, our results suggest that salinity has a profound effect on regional sea level change,’ Durack said. ‘This conclusion suggests that future sea level change assessments must consider the regional impacts of salinity-driven changes; this effect is too large to continue to ignore.‘

Attribution for the causes of observed sea level rise obviously is struggling with serious problems. No one has properly taken the changes in salinity into account.