Eric Worrall writes of a new paper trying to blame sea level rise on The Industrial Revolution, which started about 150 years ago:
The Australian National University has published a startling claim that sea level change has been more or less steady for the last 6000 years – until 150 years ago, when the sea started rising more rapidly.
According to the Abstract:
“Several areas of earth science require knowledge of the fluctuations in sea level and ice volume through glacial cycles. These include understanding past ice sheets and providing boundary conditions for paleoclimate models, calibrating marine-sediment isotopic records, and providing the background signal for evaluating anthropogenic contributions to sea level. From ∼1,000 observations of sea level, allowing for isostatic and tectonic contributions, we have quantified the rise and fall in global ocean and ice volumes for the past 35,000 years. Of particular note is that during the ∼6,000 y up to the start of the recent rise ∼100−150 y ago, there is no evidence for global oscillations in sea level on time scales exceeding ∼200 y duration or 15−20 cm amplitude.”
The abstract is at: http://www.pnas.org/content/early/2014/10/08/1411762111
The abstract notes that on longer timescales, SLR up to at least 40mm / year has been observed – so in this context “a few” mm per year does not seem particularly alarming, and is well within the range of natural variation. The fluctuation claim – the claim that sea level change in the last 150 years is faster than any change over the last 6000 years – is very much dependent on accurate dating of each of the proxy series. As we saw with the Hockey Stick controversies, any uncertainty about dating proxies tends to impose a strong hidden averaging effect on the data series, smoothing away peaks and troughs.
In any case, in many locations the current rate of change in sea level is swamped by local geological changes – one of the reasons changes in sea level are so difficult to calculate, is the land in many locations rises or falls faster than the alleged change in sea level.
But, other science suggests even higher sea levels during interglacials.
A paper published April 17th 2014 in Nature reconstructs sea levels over the past 5.3 million years and shows that sea levels were higher than the present during almost every interglacial period over the past 5.3 million years. Sea levels at present during the current interglacial are indicated as the added red horizontal line at zero meters on Fig. 2 below, and excursions above this line indicate sea levels during past interglacials as much as 50+ meters [164+ feet] higher than present sea levels. Thus, there is no evidence that sea level rise during the present interglacial is unprecedented, unnatural, unusual or any different from that which occurred in prior interglacials, or any evidence of influence by man on sea levels.
E. J. Rohling, G. L. Foster, K. M. Grant, G. Marino, A. P. Roberts, M. E. Tamisiea, F. Williams. Sea-level and deep-sea-temperature variability over the past 5.3 million years. Nature, 2014; DOI: 10.1038/nature13230
Fig. 2 with added red horizontal lines show present sea levels. Horizontal axis is thousands of years before the present.
The last interglacial ~100,000 years ago [Eemian] had sea levels between 16-31 feet higher than the present, although it appears as a tiny blip above the red line in the above graph with a much more compressed scale, but is better appreciated by this graph from another recent paper:
Sea levels during the last interglacial ~120,000 years ago were up to 5 meters higher than the present in this location and up to 9.5 meters higher at other locations (h/t to The Hockey Shtick)
So, if we had sea levels of 16-31 feet higher than the present 100,000 years ago, well before the dawn of the industrial revolution, what caused that? Inquiring minds want to know.
While climateers look for the bad in everything about our modern standard of living related to climate, this is worth noting:
In the words of Nobel Prize winning Robert E. Lucas, Jr.,
For the first time in history, the living standards of the masses of ordinary people have begun to undergo sustained growth. … Nothing remotely like this economic behavior has happened before.
Source: Landes, David S. (1969). The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to the Present. Cambridge, New York: Press Syndicate of the University of Cambridge. ISBN 0-521-09418-6.
UPDATE: Chip Knappenberger sends this graph along: