About four years ago I wrote a fairly detailed paper looking at a range of scenarios for the Gippsland coast and sea level rise. I added a postscript in May 2014 outlining possible abrupt changes if any volcanic activity under the Antarctic ice occurred. The paper considered both the possibilities of subsidence due to the lowering of the Gippsland basin aquifer and the various effects of climate change – sea level rise, increased severity and frequency of storms and storm surges. The worst case scenarios predicted were an outcome of ‘business as usual’. This state of affairs continues with big coal still the main influence in politics and with Exxon and others still removing oil and gas offshore in the Gippsland basin.
Whilst it is still ‘early days’ so far none of the predictions have materialised. There has been no measurable subsidence anywhere on the coast and sea level rise continues at a rate of about the world average – 3.5mm per annum – hardly discernible in the short to medium term. Nor have any of the storms and floods predicted occurred, or as far as I am aware, any severe erosion along the coast. As well as this the totals in the tables are substantial overestimates due to an error in my method of calculations with regards the rate of change of sea level rise and they may be one third or more too high. On the other hand it is possible that at some specific locations the rate of subsidence I have used is an underestimate. The purpose of the different scenarios is to give you a rough idea of the future, not to say what exactly will happen or when.
There are a number of problems with applying all these variables to our coast. Will the changes be abrupt or gradual? Will the rate of doubling of the amount of sea level rise be fast – about every ten to twenty years – or slow with the latter meaning the sea level rise will be just discernible over a lifetime and manageable in human terms? There are also other factors which may influence outcomes – the ‘unknown unknowns’. It is also unlikely that any subsidence will be general or uniform but may be severe in specific localities. Where it may occur is critical and combined with sea level rise subsidence at or near Golden Beach, for instance, would threaten the Gippsland Lakes system.
As well sea level rise varies substantially around the earth and the figures we use are global averages. The oceans slosh around the earth and they have measurably warmed round our coast. Whilst it easy to come to a conclusion that in a paper like mine if you can find one or more errors in it then it is all bull. However the general thrust is still valid even with allowances for subsidence and possible overestimations in my tables. The latest worst-case indicators are for sea level rise of up to 2.5 metres by 2100. Not too far off my own predictions.