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Australian sea-levels respond to CO2 by slowing down…

Posted By Joanne Nova On July 25, 2011 @ 2:20 am In Global Warming | Comments Disabled

It’s worse than we thought. The models I mean — they are more hopeless at predicting things like regional sea-level rise than we had reckoned, and we thought they were god-awful.

Remember the awe-inspiring, grant-inducing and legislation-bending Victorian report suggesting “up to 45,000 Victorian homes - worth $10.3 billion – face inundation….Across Australia 247,600 individual buildings valued at $63 billion could be damaged or lost, while major infrastructure, including Sydney and Brisbane airports, are at risk of being flooded by increasingly damaging storms.” (The airports, forgoodnesssake, were going to be underwater, and the 737′s would need those optional float thingies to “land” where there wasn’t much … land.)

Then the poor residents of Port Albert were told to build houses on stilts to avoid the feared sea-level rise (and in a double dose of bureaucratic jeopardy: at the same time they had to keep their roof-tops below the “heritage” line — making houses fit for pygmies).

Those Hollywood-style-apocalyptic flood results are based on an estimated “1.1-metre sea level rise by 2100″. Let’s think that through: current sea level is rising roughly 2mm – 3mm a year, and thus, to hit that 1.1 metre total by 2100 those global seas will need to average a rise of 12mm (“Twelve!”) a year, that’s every year for the next 90.

But a new study with the radical idea of looking at Australian and New Zealand tide gauge data (“what! actual data, not models?!”) shows that far from sea-levels around Australia rising “faster than projected”, or being at the “lower level of estimates” — they are decelerating.  The 700,000 Australian addresses that are  within 3 km of the beach don’t have so much to worry about.

The thing I like about this graph is that you don’t need to be a climate scientist to see the deceleration.

Figure 2 Relative 20-y moving average water level time series (all stations). Based on monthly average water level data provided by Permanent Service for Mean Sea Level (U.K.), National Tidal Centre (Australia), and Ports of Auckland Limited (New Zealand). Water levels have been normalised at January 1940 for direct comparison.

What’s possibly even more important, is that this new study made it to the front page of The Australian:

Sea-level rises are slowing, tidal gauge records show

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.

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”.

Here too, the wild, dangerous sea-level rise was mostly associated with the rise of Hitler and World War II, less so with CO2. Indeed in Newcastle, the seas are still not rising as fast as they were in 1942.

Figure 5: Comparison of decadal rates of change over historical record. Analysis based on relative 20-y moving average water level time series.

Article Citation:

P. J. Watson (2011) Is There Evidence Yet of Acceleration in Mean Sea Level Rise around Mainland Australia?. Journal of Coastal Research: Volume 27, Issue 2: pp. 368 – 377.

doi: 10.2112/JCOASTRES-D-10-00141.1 [Link Abstract PDF ]
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