Local government councils and sea-level rise

The Eurobodalla Shire Council (ESC), of which I am a ratepayer, has written to me letting me know that I might be contacted soon as part of a community outreach survey. The Council wants to ask for a special rate increase to fund new infrastructure projects, and needs to know what we ratepayers think, because ‘your rates are the Council’s main source of income’. Council has helpfully provided information about what it proposes to do if the increased rates are provided. They seem fine to me.

Nothing in the information talks about sea-level rise, but ESC and the adjoining Shoalhaven City Council are also worrying about what to do with the IPCC forecast of large rises in sea-level over the remainder of the century and beyond, and have commissioned a report from a consultant, in this case Whitehead and Associates, which you can download from here.

Whitehead and Associates, according to its website, operates in the fields of on-site and decentralised wastewater management, soil and water management, waste and landfill management and environmental geology. It has done a deal of work of that kind. For this job it took on as partner Coastal Environment Pty Ltd, which describes itself as a specialist coastal, estuarine and port engineering consultancy built around the experience and expertise of the principal of the company…

Now since our own property in Eurobodalla Shire, though adjacent to the sea, is also some thirty metres above it, we have no immediate anxiety. But since I have an interest in this much-debated issue, I thought I would read the consultants’ report and see what I thought. It didn’t take me long to become somewhat alarmed.

While the Disclaimer says in part that Limits to understanding climate change science, predicting future emissions and projecting future sea-level rise, mean that there is significant uncertainty and absolute predictions cannot be reliably made, the rest of the Report seems to have forgotten that caveat entirely.

The experts go quickly to the IPCC’s AR5 and pronounce as follows (emphasis in the original): Having reviewed the IPCC’s AR5 report, we have found it to provide a balanced representation of the present state of the science, including discussions relating to uncertainty and possible errors in assessment. We consider that the modelled projections from the IPCC’s AR5 report are ‘widely accepted by competent scientific opinion’ … [and] form a suitable basis for deriving local projections of relevance to the study area.

Oh my goodness! Just as these days everyone needs a medical advocate to speak for them to nurses, doctors and hospitals, when hospital is where they are going, local government councils need some kind of disinterested research advocate to help them deal with advice like this. Does anyone on ESC know, for example, that these modelled projections have little validity, that the models themselves have never been verified or validated, and that where models have tried to predict temperature they have overstated the real outcome again and again? Why would you use them for sea-levels?

It gets worse. The consultants have decided to recommend the IPCC’s  Representative Concentration Path (RCP) 8.5 projection, which assumes an astonishingly large accumulation of CO2 in the atmosphere by the end of the century, and  provides (after their analysis of current sea levels, which seem very high to me) nearly a metre increase in sea levels on the South Coast by 2100, and half a metre by 2070. What is the probability of such increases occurring? On the observational evidence so far, a very small probability indeed.

Fortunately, another set of experts has stepped in to help the two Councils, and you can read their account here. I know the leader author, Professor Bob Carter, and have a high opinion of his technical skill and his common sense. He is a palaeontologist with an international standing. Several of the other authors I know by reputation, and some are experts about sea-levels here and around the world. Their report has been offered as friendly advice to the Councils, by those who read the other report and thought it was so wrong that it ought not to be followed in policy-making.

They too see the IPCC Report as the wrong basis for policy: no effective coastal management plan can rest upon speculative computer projections regarding an idealised future global sea-level, such as those provided by the … IPCC. Coastal management must instead rest upon accurate knowledge of local geological, meteorological and oceanographical conditions, including, amongst other things, changes in local relative sea level.

The last is a most important point. Average global sea levels don’t mean much when you are talking about a specific location. Coastal areas can be sinking or rising because of geological changes, and these changes can be much more significant than changes brought about in the volume of the oceans. As it happens, the South Coast of NSW is geologically pretty stable, while the annual rate of sea-level increase at Fort Denison in Sydney, not so far away, has been tiny — about 1mm or less since the 1880s. Some recent studies suggest that the rate is decreasing.

The Whitehead and Associates Report says the average annual rise is 3.3 mm, which is larger than any figure I have recently come across for sea-level rise in the past twenty years. Carter et al say that the consultants have done this by considering only very recent Fort Denison data, processing the data in an unexplained way and relying on models, not on actual data.

The NSW Chief Scientist advised Councils some time ago that they should use the closest available long-term tide-gauge measurements when they were formulating policies on coastal management. Carter et al conclude that the likely 7.3cm rise [not a metre!]in local sea level in NSW over the next 100 years is too small to justify a major planning response.

Speaking as a financially disinterested ratepayer, I strongly agree, and suggest to the ESC that it file the Whitehead and Associates Report in a bottom drawer somewhere, and get on with the infrastructure projects that it wants the rate increase for.



Join the discussion 15 Comments

  • Peter Kemmis says:

    Your account of the Whitehead report reminds me of the time when senior executives, faced with a decision about obtaining new computer equipment, knew that if they chose IBM, their jobs would always be safe.

    While I think the commentary from Bob Carter et al. is enlightening, I wonder whether the Councillors will look at the time scale of the chart, and shrug their shoulders. The typical local councillor is generally a hard-working and reasonably educated person, hammered from all sides with every kind of demand – but not used to digesting argument in academic language. True, the Carter advice is plain speaking, but there are some very strong additional rebuttals to the Whitewash that could be made.

    Probably charts of the last 100+ years along the eastern seaboard, would mean more to them. A few temperature observations since the 1850s would also help, together with sea ice variations based on measurements and reports over the last hundred years. As well, I’d throw in a few of the failed IPCC predictions about future temperatures and ocean levels, augmented with the model’s famous temperature charts, and topped off with some Flummeries.

  • Mike says:

    I think the councils should take a very practical approach to all of this. The question to be asked is are they liable? If someone wants to build by the sea and the council is agreeable, with caveats that any act of God beyond their control that damages the property is nothing to do with them who cares. In the USA there is a group that will apply a computer model to see if it’s safe or not. The model is completely useless but seems to keep everyone happy so what the hell. Rule of thumb is if you can fish from your balcony you are too damn close.

  • Patrick Caldon says:

    “that the models themselves have never been verified or validated, and that where models have tried to predict temperature they have overstated the real outcome again and again?’

    Irrespective of the truth of this statement, why are you not discussing the performance of models on sea-level? Surely that’s the relevant datum.

    • Don Aitkin says:

      Carter et al deal with this. The problem is that the models refer to ‘global sea level’ and and its relationship with ‘global temperature’. That is of little use to people living in Batemans Bay, who want to know what will happen there. The NSW Chief Scientist told them to look at what had happened over the period since the nearest tide gauge was established, and the nearest tide gauge to them is Fort Denison, where nothing of any consequence has happened for a very long time.

      There have been many attempts to produce local or regional models from the global ones, but so far none of them has been at all useful. Their application to local tide gauge data is in its infancy, as you can see from the work of Perez and others, at

      where they try out models with mostly Spanish data.

      • Mike says:

        Don let’s get down to facts why the hell are the councils concerned? Are they liable if existing houses get flooded because of the sea or other reason? There were many houses that were flooded in Brisbane a while back and they were on a recognised floodplain it seems all is settled now with no great dramas. If you buy a house surely the onus is on the buyer to check these issues out not the Council.

        • Don Aitkin says:

          I think the answer is that the previous Labor Government in NSW got them properly scared about their legal responsibilities if sea levels rose and Councils had not warned residents or done anything about sand dunes etc. The coalition government has taken a much more laissez faire approach. But many councils have a core of Greenish councillors who ‘believe’ in AGW and want ACTION NOW.

          • Gus says:

            “>>>But many councils have a core of Greenish councillors who ‘believe’ in AGW and want ACTION NOW.<<<"

            Just vote them out of office. Can't you?

          • Don Aitkin says:

            Not easily. Coastal shires have a lot of residents who are environmentally active, and that has benefits in the case of ESC, which has not been spoiled by over-development. Unfortunately, being environmentally active tends to lead to an acceptance of AGW, belief in the virtues of the IPCC, and all the rest. My guess, from the correspondence I’ve had with Councillors, is that AGW is accepted by a majority of them.

      • Patrick Caldon says:

        It doesn’t really address the point of comparing modelled vs actual, which is the point you yourself raised. You asked why would someone employ a model when it over predicts – as I say that’s entirely debatable given the substantial variability in temperature – but in this case, there’s a lot less variability in sea level, and the models have a track record of consistently under predicting sea level rise. What relevance to local/regional? The numbers they’re suggesting – with a track record of underprediction – will swamp the relatively smaller changes over the last 100 years come 100 years hence and be greater than regional variation if you assume the land mass is stable.

        • Don Aitkin says:

          I’m not sure how to answer, Patrick, because I’m not sure quite what you’re saying. There is abundant evidence on tide gauges over the last 100 to 150 years. The data vary from place to place, but they all show a slow rise. The IPCC uses these data to model the future, but their assumptions, like those used by the consultants on this case, come with a lot of ifs and maybes, and the outliers look frankly risible.

          What is this ‘track record of underprediction’? Measuring sea levels is a tricky business at the best of times, and finding out the causes, and the causes of the causes, is by no means settled either.

          And you don’t think the models are running too hot? Even the IPCC admits it’s a possibility.

          • Patrick Caldon says:

            Refer to Figure 13.7 in the latest WG1 report. See figure (a). The CMIP5 models (solid black line) substantially underestimate past sea level. By adding a series of estimates for ice sheet and glacier loss – perhaps plausible estimates, but nevertheless pretty basic, based on the idea that ice-sheet warming got “baked in” some time ago – you can get to the dotted line. The black line is a long way below the measured data.

          • Don Aitkin says:

            That’s not a ‘track record’, and indicates to me that the models are not very good. In any case, they are about global sea level, not what happens south of Sydney NSW.

          • Patrick Caldon says:

            The projections haven’t changed much for the last 20 years Don.

      • Gus says:

        If your property is somewhere near Bateman’s Bay, it may well be that the sea level, with respect to the ground in that location, is actually… falling. This is the case pretty much everywhere on the US Pacific Coast and is caused by the movement of the continental plate, which is being uplifted as the continent drifts west against the movement of the oceanic crust.

        There is, I think, something similar in Australia, which is known to drift in the north-west direction.

  • Gus says:

    Here are some papers you may wish to quote if you’d like to argue the matter with the council.

    1. doi:10.1016/j.quascirev.2012.09.006, “Post-glacial sea-level changes around the Australian margin: a review”, Lewis et al., Quaternary Science Reviews, 2012: Sea level around Australia was about 1 m higher than at present, 7000 years ago.

    2. doi:10.5194/osd-11-2029-2014, “Improved sea level record over the satellite altimetry era (1993–2010) from the Climate Change Initiative Project”, Ablain et al., Ocean Science Discussion, 2014: Sea level rise decelerated by 31% since 2002 and by 44% since 2004 to less than 7 inches/century. The positive global sea level rise is due almost entirely to a bulge in the western Pacific, with all other areas experiencing drop in the altimetric sea levels between 1993 and 2010. The combination of ARGO and GRACE finds the sea level rise to be 2.31 mm/year, which is 35% less than the rise determined from satellite altimetry.

    3. doi:10.1002/2013GL059039, “Evidence for a differential sea level rise between hemispheres over the 20th century”, Woppelmann et al., Geophysical Research Letters, 2013: The spatial coherence in the rates of sea level change during the 20th century is highlighted at the local and the regional scales, ultimately revealing a clearly distinct behavior between the northern and the southern hemispheres with values of 2.0 mm/year and 1.1 mm/year, respectively.

    Hope this helps.

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