No Acceleration of Global Sea-Level, II

Stuart Rintoul, in The Australian, reveals that despite our Government’s hysterical claims that the world’s sea-levels will rise alarmingly, a government expert explains that the rises are decelerating.   In “Sea-level rises are slowing, tidal gauge records show”, Rintoult writes:

One of Australia’s foremost experts on the relationship between climate change and sea levels has written a peer-reviewed paper concluding that rises in sea levels are “decelerating”.

The analysis, by NSW principal coastal specialist Phil Watson, calls into question one of the key criteria for large-scale inundation around the Australian coast by 2100 – the assumption of an accelerating rise in sea levels because of climate-change.

Based on century-long tide gauge records at Fremantle, Western Australia (from 1897 to present), Auckland Harbour in New Zealand (1903 to present), Fort Denison in Sydney Harbour (1914 to present) and Pilot Station at Newcastle (1925 to present), the analysis finds there was a “consistent trend of weak deceleration” from 1940 to 2000.

Mr Watson’s findings, published in the Journal of Coastal Research [...] supports a similar analysis of long-term tide gauges in the US earlier this year.  Both raise questions about the CSIRO's sea-level predictions.

Climate-change researcher Howard Brady, at Macquarie University, said yesterday the recent research meant sea levels rises accepted by the CSIRO were “already dead in the water as having no sound basis in probability”.

“In all cases, it is clear that sea-level rise, although occurring, has been decelerating for at least the last half of the 20th century, and so the present trend would only produce sea level rise of around 15cm for the 21st century.”

Dr Brady said the divergence between the sea-level trends from models and sea-level trends from the tide gauge records was now so great “it is clear there is a serious problem with the models”.

“In a nutshell, this factual information means the high sea-level rises used as precautionary guidelines by the CSIRO in recent years are in essence ridiculous,” he said.  During the 20th century, there was a measurable global average rise in mean sea level of about 17cm (plus or minus 5cm).  [...]

The federal government has published a series of inundation maps [...] showing that large areas of Australia’s capital cities, southeast Queensland and the NSW central coast will be under water by 2100.

Without acceleration in sea-level rises, the 20th-century trend of 1.7mm a year would produce a rise of about 0.15m by 2100.

Mr Watson’s analysis of the four longest continuous Australian and New Zealand records is consistent with the findings of US researchers Robert Dean and James Houston, who analysed monthly averaged records for 57 tide gauges, covering periods of 60 to 156 years.

The US research concluded there was “no evidence to support positive acceleration over the 20th century as suggested by the IPCC, global climate change models and some researchers”.

See P.J. Watson, “Is There Evidence Yet of Acceleration in Mean Sea Level Rise around Mainland Australia?” in the Journal of Coastal Research. 

See also our “No Acceleration of Global Sea-Level, I” and, at WUWT, “The battle over sea level”.

No Acceleration of Global Sea-Level, I

The renowned, crazed NASA employee, Dr James Hansen, a notorious, irrationally misanthracist fruitcake, has predicted that sea-levels may rise five metres a century or (on days when his navel lint sends messages by way of his breakfast cereal, perchance) over twenty-five metres.*  The famed, award-winning profiteer of doom, Al. Gore, a serial liar, has predicted that sea-levels will rise by more than seven metres by the end of this century.†  The late Robyn Williams predicted a rise of one hundred metres.  In the Fourth Assessment Report (4AR) of the Intergovernmental Panel on Climate Change (IPCC), however, Bindoff et al. (2007) project a global sea-level rise relative to 1990 of up to 79 cm by 2100.  The data suggest that even the less outrageous predictions of Prof. Bindoff et alii are unlikely to occur.
From J.R. Houston and R.G. Dean, “Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses” in the Journal of Coastal Research:

The current sea-level trend of about 1.7 mm/y will produce a rise of about 19 mm [sic‡] over 110 years from 1990 to 2100, but a rise to 79 cm will require an acceleration of about 0.10 mm/y² [...].

Our analyses do not indicate acceleration in sea level in U.S. tide gauge records during the 20th century.  Instead, for each time period we consider, the records show small decelerations that are consistent with a number of earlier studies of worldwide-gauge records.  The decelerations that we obtain are opposite in sign and one to two orders of magnitude less than the +0.07 to +0.28 mm/y² accelerations that are required to reach sea levels predicted for 2100 by Vermeer and Rahmsdorf (2009), Jevrejeva, Moore, and Grinsted (2010), and Grinsted, Moore, and Jevrejeva (2010).  Bindoff et al. (2007) note an increase in worldwide temperature from 1906 to 2005 of 0.74ºC.  It is essential that investigations continue to address why this worldwide-temperature increase has not produced acceleration of global sea level over the past 100 years, and indeed why global sea level has possibly decelerated for at least the last 80 years.^§

UPDATE:  see “A Fairy Tale:  Jimmy and the Lump of Coal”.

*  Hansen, in “Climate Change:  On the Edge”, writes, “How far can it go?  The last time the world was three degrees warmer than today—which is what we expect later this century—sea levels were 25m higher.  So that is what we can look forward to if we don’t act soon.”

†  see, for example, earlier posts here and here.

‡  110 years of 1.7 mm a year would equal 187 mm or about 19 cm, not 19 mm.
UPDATE II:  James R. Houston kindly responded to an enquiring e-mail, writing that the “mm” is indeed an error for “cm”.
§  of course, one simple explanation could be that temperatures did not rise by 0.74ºC.