Wednesday, August 8, 2012

New paper finds sea level rise has greatly decelerated over past 10 years

A paper published in Coastal Engineering finds the rate of sea level rise has greatly decelerated over the past 10 years, which "is clearly the opposite of what is being predicted by the models," and that "the [sea level rise] reduction is even more pronounced during the last 5 years."

As reported today by the NIPCC Report:

Reference: Boretti, A.A. 2012. Short term comparison of climate model predictions and satellite altimeter measurements of sea levels. Coastal Engineering 60: 319-322.

Boretti (2012) begins his work by noting that in its report of 2007, the IPCC projected that global sea level was likely to rise somewhere between 18 and 59 cm by 2100; but he says that certain "model-based analyses performed recently have predicted much higher sea level rise [SLR] for the twenty-first century," even "exceeding 100 cm if greenhouse gas emissions continue to escalate," citing most pointedly in this regard the studies of Rahmstorf (2007, 2010). However, he notes that studies reaching just the opposite conclusion have also been published, referencing those of Holgate (2007), Wunsch et al. (2007), Wenzel and Schroter (2010) and Houston and Dean (2011).
Working with what he calls "the best source of global sea level data," which he identifies as the TOPEX and Jason series of satellite radar altimeter data, Boretti applies simple statistics to the two decades of information they contain to "better understand if the SLR is accelerating, stable or decelerating." So what did he find?
The Australian scientist reports that the average rate of SLR over the almost 20-year period of satellite radar altimeter observations is 3.1640 mm/year, which if held steady over a century would yield a mean global SLR of 31.64 cm, which is just a little above the low-end projection of the IPCC for the year 2100. However, he also finds that the rate of SLR is reducing over the measurement period at a rate of -0.11637 mm/year2, and that this deceleration is also "reducing" at a rate of -0.078792 mm/year3.

Comparison of MSL predictions from Rahmstorf (2007) with measurements from the TOPEX and Jason series. Adapted from Boretti (2012), who states in the figure caption that "the model predictions [of Rahmstorf (2007)] clearly do not agree with the experimental evidence in the short term."
Commenting on these findings, Boretti writes that the huge deceleration of SLR over the last 10 years "is clearly the opposite of what is being predicted by the models," and that "the SLR's reduction is even more pronounced during the last 5 years." To illustrate the importance of his findings, he notes that "in order for the prediction of a 100-cm increase in sea level by 2100 to be correct, the SLR must be almost 11 mm/year every year for the next 89 years," but he notes that "since the SLR is dropping, the predictions become increasingly unlikely," especially in view of the facts that (1) "not once in the past 20 years has the SLR of 11 mm/year ever been achieved," and that (2) "the average SLR of 3.1640 mm/year is only 20% of the SLR needed for the prediction of a one meter rise to be correct."
Clearly, the more-rabid-than-the-IPCC-crowd has it all wrong when it comes to both sea level and climate, for as Boretti concludes, "the oceans are truly the best indicator of climate," and what they suggest is not compatible with what those alarmed about climate change continually claim.
Additional References
Holgate, S.J. 2007. On the decadal rates of sea level change during the twentieth century. Geophysical Research Letters 34: 10.1029/2006GL028492.
Houston, J.R. and Dean, R.G. 2011. Sea-level acceleration based on U.S. tide gauges and extensions of previous global-gauge analyses. Journal of Coastal Research 27: 409-417.
Rahmstorf, S. 2007. A semi-empirical approach to projecting future sea-level rise. Science 315: 368-370.
Rahmstorf, S. 2010. A new view on sea level rise: has the IPCC underestimated the risk of sea level rise. Nature Reports Climate Change:10.1038/climate.2010.29.
Wenzel, M. and Schroter, J. 2010. Reconstruction of regional mean sea level anomalies from tide gauges using neural networks. Journal of Geophysical Research 115: 10.1029/2009JC005630.
Wunsch, C., Ponte, R. and heimbach, P. 2007. Decadal trends in sea level patterns: 1993-2004. Journal of Climate 20: 5889-5911.


  1. Great article, with one reservation... the headline talking of sea level "greatly decelerating" sounds like it was really rising a lot before, and still is, just decelerated.
    For those that have unfortunately been around, and been to the beach, use our own eyes. No matter where we are, from sea to shining sea, we can see that the sea has not risen in decades. Not at all. I know, there are "adjustments" to be made that will create the "data" showing that our own eyes are full of it. Bull.

  2. It is also worth noting that satellite measurements begin in 1993. Church & White comment

    However, the reconstruction indicates there was little net change in sea level from 1990 to 1993, most likely as a result of the volcanic eruption of Mount Pinatubo in 1991.

    In other words, the trend is calculated from an unusually low point.


  4. Can someone tell me why the sea level "rises" in some areas greater or lesser than areas two or three hundred miles away? Is it just possible that the land mass may be sinking in different areas at different rates?

    1. Correct at any given time, the land can rise and fall, due to changes in the outer core, continents hitting one another etc

      So one area can rise and less then 100km away it can be falling.