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Will Rising Seas Swamp Sydney, Australia by Century's End?
Volume 15, Number 45: 7 November 2012

Alberto Boretti, Associate Professor of Engineering at the University of Ballarat's School of Science and Engineering in Ballarat, Australia, has a problem with recent pronouncements of the Australian government, which is providing information to the country's citizens that depicts, in the near future, "floods and mass relocations due to the rise of sea levels resulting from increased carbon dioxide emissions." He reports, for example, that "low-lying coastal areas, where the majority of Australians are concentrated, have been declared at risk of sea level inundations," and that "maps with 0.5, 0.8 and 1.1 meter sea level rise have been proposed for Sydney, the major Australian city." But are there any real-world data to justify this scare-mongering?

In an effort that looks to actual historical measurements of sea level change for enlightenment, Boretti consults "long term tide gauges recording sea levels worldwide as well as along the coastline of Australia and within the bay of Sydney." And what does he find?

Firstly, Boretti reports that "the worldwide average tide gauge result obtained considering all the data included in the Permanent Service for Mean Sea Level data base show a modest sea level rise and about zero acceleration." Second, he notes that "the Fort Denison, Sydney tide gauge result shows the same modest sea level rise and about zero acceleration in perfect agreement with the worldwide result." Third, he indicates that "the Fremantle tide gauge result, the only other tide gauge operational in Australia over more than a century, shows the same modest sea level rise and about zero acceleration in perfect agreement with the worldwide result and the result of Sydney." And fourth, he indicates that "the other tide gauges operational along the coastline of Australia over shorter time scales of 30 to 40 years on average also show the lack of any acceleration component in the rate of rise of sea levels."

In completing his analysis, Boretti thus concludes, quite logically, that the "rise of sea level in the bay of Sydney by 2100 is therefore more likely less than the 50 mm measured so far over the last 100 years, rather than the meter [1000 mm] predicted by some models," the latter of which would appear to be the source of "inspiration" for the Australian government's pronouncements.

Our advice to the Australian government would consequently be to get real, i.e., to get real data, before making any further outlandish pronouncements on the subject of potential future sea level change.

Sherwood, Keith and Craig Idso

Boretti, A. 2012. Is there any support in the long term tide gauge data to the claims that parts of Sydney will be swamped by rising sea levels. Coastal Engineering 64: 161-167.