Saturday, May 17, 2014

New paper finds sea levels rising only 7 inches per century with no acceleration

Global Sea Level Behavior of the Past Two Centuries

CO2 Science May 14, 2014

Reference: Jevrejeva, S., Moore, J.C., Grinsted, A., Matthews, A.P. and Spada, G. 2014. Trends and acceleration in global and regional sea levels since 1807. Global and Planetary Change 113: 11-22.

The authors write that "satellite altimetry measurements since 1993 have provided unique information about changes in global and regional mean sea levels," suggesting a mean rate of rise of 3.2 mm/yr for global sea level over the period 1993-2012 (Boening et al., 2012; Cazenave et al., 2012), which "notably exceeds the estimate of 1.8 mm/yr sea level rise for the 20th century (Bindoff et al., 2007)." So which rate is closest to the truth?

What was done
In a study designed to answer this question, Jevrejeva et al. (2014) say they "renew the global sea level [GSL] reconstruction by Jevrejeva et al. (2006), using monthly mean sea level data collected by the Permanent Service for Mean Sea Level (PSMSL) covering the observations from 1807 to 2010," thereby improving the GSL reconstruction by increasing data coverage "by using many more stations, particularly in the polar regions, and recently processed historic data series from isolated island stations," as well as by extending the end of the reconstruction from 2002 to 2009.

What was learned
Quoting the five researchers, "the new reconstruction suggests a linear trend of 1.9 ± 0.3 mm/yr [7.5 inches per century] during the 20th century" and "1.8 ± 0.5 mm/yr [7 inches per century] for the period 1970-2008."

What it means
Although some regions have recently experienced much greater rates of sea level rise, such as the Arctic (3.6 mm/yr) and Antarctic (4.1 mm/yr), with the mid-1980s even exhibiting a rate of 5.3 mm/yr (Holgate, 2007), this newest analysis of the most comprehensive data set available suggests that there has been no dramatic increase - or any increase, for that matter - in the mean rate of global sea level rise due to the historical increase in the atmosphere's CO2 concentration.[Therefore, there is no evidence of any human influence on sea levels]


Bindoff, N.L., Willebrand, J., Artale, V., Cazenave, A., Gregory, J., Gulev, S., Hanawa, K., Le Quere, C., Levitus, S., Nojiri, Y., Shum, C.K., Talley, L.D. and Unnikrishnan, A. 2007. Observations: Oceanic climate change and sea level. In: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L. (Eds.). Climate Change 2007: They Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom.

Boening, C., Willis, J.K., Landerer, F.W., Nerem, R.S. and Fasullo, J. 2012. The 2011 La Niña: So strong, the oceans fell.Geophysical Research Letters 39: 10.1029/2012GL053055.

Cazenave, A. Henry, O., Munier, S., Meyssignac, B., Delcroix, T., Llovel, W., Palanisamy, H. and Becker, M. 2012. Estimating ENSO influence on the global mean sea level, 1993-2010. Marine Geodesy 35: 82-97.
Holgate, S.J. 2007. On the decadal rates of sea level change during the twentieth century. Geophysical Research Letters34: 10.1029/2006GL028429.

Jevrejeva, S., Grinsted, A., Moore, J.C. and Holgate, S. 2006. Nonlinear trends and multi-year cycle in sea level records.Journal of Geophysical Research 111: 10.1029/2005JC003229.

Reviewed 14 May 2014


  1. Dear Sir, what is your opinion about the recent findings from the Cyrosat sattelite that measued antarctic sea melting?

    1. It's difficult to believe Antarctica is losing ice at increasing rates given record sea ice extent, and no acceleration of sea level rise. In fact, Cazenave et al 2014 finds sea level rise has decelerated 31% since 2002.

  2. I think the recent satellite measurements of Antarctic ice loss just show natural processes at work. The net loss of 160 Gt/year sounds quite high, but is the relatively small difference between ice forming and melting, each around 2000 Gt/year.

    Much hype in the media of course that it must all be our fault, and so we should take urgent action, etc.

    1. The 160 Gt/year is equivalent to about 0.43 mm/yr of sea level rise, or equivalent to 25% of the Jevrejeva et al 2014 sea level rise figure of 1.8 mm/yr. However, it is still twice the Sheppard et al 2012 (Sciencemag) 81 Gt/year figure for 2005-2010. This could be accounted for in the measurement techniques. The recent study is based on actual measurements from Cryostat-2 satellites, which is accurate to as little as 1.3cm. It is impressive accuracy, but in Antarctica there is much lower rates of annual accumulation, with large calving at the periphery - particularly in Western Antarctica at the present time. A layer of ice of 1mm spread over all of Antarctica would weigh over 10 gigatonnes. The difference might be accounted for by measurement bias. More data from Cryostat-2 will demonstrate if the is the case. If I am right, the data will come more into line with the GRACE measurements

  3. There have been various studies over the past few years of years of polar ice-cap melt. All show acceleration in the rate of ice melt within the study period and many say that it is "worse than we thought". Try researching Velicogna and Wahl 2006, Velicogna 2009, Rignot, Velicogna 2011, or Sheppard et al 2012. That latter two start from 1993, assuming the net rate of polar ice loss was zero in that year.
    There is a reconciliation issue with these studies, compared to sea level rise. The satellite data from shows a constant level of sea level rise of 3.2 mm/yr for the last 20 years, Jevrejeva et al. (2014) just 1.8 mm/yr for 1970-2008. What they do not show is an acceleration in rate of sea level rise. If both Rignot, Velicogna 2011 & Jevrejeva et al. (2014) are correct, then between 1993 and 2010 the proportion of sea level rise due to polar ice cap melt increased from 0% to 100% of the sea level rise. So what declined? If Kevin Trenberth is to believed, it was not due to rapidly declining ocean temperatures.

    1. Yes that's right, the sea level budget is not compatible with either accelerated melt of the ice caps or accelerated "missing heat" in the oceans, since sea level rise is stable or possibly even decelerating.