Friday, January 29, 2010

More on the future of Canberra rainfall

The above publication, from 2004, discusses options for the future of Canberra's water supply. There are two things that stand out for me: firstly, the area that they are counting on for future water supplies has declined since 2003 from a five-year annual average of 830 mm to 630 mm (and 830 mm was already 90 mm below the long-term average ...); and secondly, the worst-case scenario prediction for rainfall decline for Canberra by 2030 is 9 per cent.

The data for the Brindabella region is here:

Now, it is possible that we are only talking about a short-term fluctuation in rainfall over the last little while, and that there will be a rebound in the near future that will take us back up to that 9 per cent decline or better position by 2030. But the evidence is that this will not be the case: it looks as though rainfall patterns in Australia have altered.

It should be noted that the predictions from the CSIRO and the IPCC are based on models that have very poor resolution at local levels. They can predict global climate quite well, but for regional climate - and regional rainfall/precipitation in particular - they are not able to do very well.

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