Predicted Climate in the Murray-Darling region
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| 1. Observational data used on this web page is available from the Australian Bureau of Meteorology at this page. | |
Introduction |
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Climate predictions are being used in Victoria (a state in south-eatern Australia) as justification
for the conservation of water. There is no argument that conserving water is a good practice but one
must wonder about the integrity of those who imply that predictions from one or more climate models
are accurate when data from weather observations shows just how wrong those predictions are. Just as worrying is the thought that politicians may be spending public money on the basis of poor predictions, never mind the fact that the politicians have endorsed the documents in which the predictions appear. |
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| Below is the graph which appears in
"Securing Our Water Future" and "Securing Our
Water Future Together", both publications of the
Victorian government's Department of Sustainability and
Environment, as well as in publications by various water
supply authorities in the state of Victoria. |
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This graph appears with no explanation - not even for "Max. temp.
change" which could mean either the maximum change in Mean
Temperature or the predicted change in Maximum Temperature. The text accompanying the graph in "Securing our Water Future Together" states: "In the Murray-Darling Basin, annual temperatures are projected to increase by up to two degrees by 2030 and up to six degrees by 2070." (No, I can't see where they got 6 degrees by 2070 from either!) In "Our Water Future" we find "Annual temperature is projected to increase by 0.4 to 2 degrees by 2030 and by 1 to 6 degrees by 2070 in the Murray Darling Basin. This will mean less water for everyone". (No, I can't see the direct connection between temperature and rainfall either. Predictions for other regions around the world often say "hotter and wetter" so we can't assume that hotter implies drier.) Dubious interpretations of the predictions aside, it is already evident that the predictions are nonsense. |
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Accuracy of the Model - Temperature |
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The predicted temperature - or whatever the term "Max. temp. change" means - bears no similarity to the
data recorded from official observations for the Bureau of Meteorology. The two graphs are shown below. On the left, the graph of predicted temperatures and on the right, the annual and 5-year running averages of the mean observed temperatures from 1960 to 2004. The period of averaging (if that is what is shown in the graph of predicted temperatures) may be different but there is no confusion with annual values. |
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Accuracy of the Model - Rainfall |
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The predicted rainfall to date (shown below) also shows no similarity to the levels recorded. Generally speaking, the recorded levels of rainfall across the Murray-Darling Basin between 1960 and 2004 were about double the levels predicted. Even though the decline is exaggerated by the (unfulfilled) prediction of higher rainfall in the early 1960s, the overall rate of declining trend is not significant. The indicated decline is about 40mm in 140 years, equivalent to about 3mm per decade. The trend line from the observed rainfall levels from 1960 to 2004 indicates a decline of even less than the tiny amount predicted, just 0.15mm per year (equivalent to 1.5mm per decade, or 15mm - i.e. on the old scale, just over half an inch - per a century). |
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Comments |
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| Predicted temperatures and rainfall for the Murray-Darling Basin for the period 1960-2004 are absolute nonsense and deserve no credibility whatsoever. Basing political decisions on these predictions shows scant regard for science or for honesty, but it reeks of political opportunism. | |
| Of course it is possible that the two graphs deal with different regions
but those government publications have certainly not made that clear. If that is the case, then the
Victorian government could be accused of incompetence rather than deliberate deception. |
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| You might also wonder why predictions for periods since 1960 were made
in 2003 - more than 40 years after the start of the period -
when data from observations was readily available
and showed how incorrect those predictions were. I have no idea either, but maybe somebody thought the information would be taken at face value or that the predicted changes would look even worse if they started from that earlier date. It wouldn't be the first time that these things have happened; just look at a lot of the discussion about climate change! |
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