What is the risk of sea level increases?
Although there was little debate during the election about climate change policies, a lot of action has been going on behind the scenes on sea levels. This reflects the acceptance by our governments of questionable sea level projections in the Intergovernmental Panel on Climate Change 2007 Fourth Assessment Report and even of extensions of these projections to unrealistic levels on advice from the CSIRO. This has led State planning authorities and councils to start introducing restrictions on property development in low lying areas and the associated fall in seaside prices in some areas has been reflected in downward official valuations of such properties.
In Victoria, for instance, the development issue went to VCAT and it refused permission for a small beachside project at Lakes Entrance. At the VCAT hearing reference was made to a federal government report warning that up to 44,600 Victorian homes could be destroyed by 2100 by rising sea levels.
Careful analysis of the sea level situation indicates, however, that the risk of extensive flooding of low lying areas in Australia is remote and that State governments and councils are behaving irresponsibly. Indeed those holding developable land in many low lying areas may have a legal case for challenging decisions such as the VCAT one.
Let us look at the basis on which sea level projections have been made.
First, based on a “series of scenarios” of the future and its best-guess temperature projection of 2.4-4.5C degrees to 2100 unless countervailing action is taken, the 2007 IPCC report included a projected increase in average global sea levels to 2100 ranging between 18 and 59 cm.
Next, in March 2010 the CSIRO and the Bureau of Meteorology jointly published a State of Climate report on their assessment of the implications for Australia of the IPCC projections. The report accepts those IPCC temperature projections, concludes that the rate of global sea level rise increased in the 20th century and has an accompanying graph showing an increase of about 15 cm, or about 1.5 cm per decade. The report states that from 1993 to 2009 sea level rise has been 1.5 to 3 cm per decade in the south and east of Australia. A continuation of that rate would result in an increase to 2100 close to the lower end of the IPCC’s predicted range.
However, a 2009 report by the CSIRO for the Victorian Government’s Future Coasts Program on The Effect of Climate Change on Extreme Sea Levels in Port Phillip Bay took it much further. While it acknowledged that projections of sea levels “are inherently uncertain”, this CSIRO report based its figuring on temperature projections to 2100 of up to 6.4 degrees. That is the most extreme, fuel intensive, scenario of the IPCC and implies unbelievable CO2 concentration levels in 2100 of approximately 1550 parts per million (expressed in CO2 equivalent). Usage of all known fossil fuel reserves would only achieve half of this and continuation of the current rate of increase in concentration levels would result in only 550 ppm by 2100.
In terms of sea levels, the result is a CSIRO predicted rise for Port Phillip Bay by 2100 of 82 cm and, with the help of the Bureau of Meteorology, an increase due to wind to 98 cm. That is not only well above even the top level projected by the latest IPCC report but is also well above any projections from the last 20 to 100 years.
Such analyses have naturally drawn increased attention to possible sea level increases and low-lying flooding. The alleged threat has been enhanced by recent reports that Greenland has shed the largest slab of ice since 1962, causing one geo-science professor to attract attention by warning a US Congressional hearing on global warming that, if temperatures rose by up to 7 degrees, the Greenland ice sheet could be obliterated and sea levels could rise by 7 metres. However, a US professor of ocean science acknowledged in an interview on the ABC that he could not say “if global warming is at work or not”. Other analysts have also pointed out that the “calving” of ice from Greenland occurs regularly and that, while this one maybe four times the size of Manhattan, that would be only about 0.02 per cent of the Greenland ice sheet.
As with many analyses by scientific groups working on climate issues, the CSIRO tends to advocacy and not assessment. This leads to exaggeration of the global warming problem. In the present case the exaggerations extend beyond even those of the IPCC, whose reports are currently under review by an Inter-Academy committee in the UK. This is highlighted in the failure of the CSIRO report for the Victorian Government to express any uncertainties of projection and methodology that might suggest it is simply a computer-modelled projection.
This despite the satellite measurements of global sea levels since 1993 showing an increase of only 5 cm to 2010. A continued increase at that rate would result in a further sea level rise of 25 cm by 2100. On any reasonable assessment of likely sea levels, there is no scientific basis for restrictions on property development in low-lying coastal areas in Australia.
Des Moore is Director, Institute for Private Enterprise and Tom Quirk a sometime Oxford physicist.