|In March 2005 CSIRO
reported to Melbourne Water on the "Melbourne Water Climate Change
Study" which can be downloaded in pdf
format at; http://www.melbournewater.com.au/ This
report could be summed up as the usual CSIRO Greenhouse model driven
paean to warmer/dryer times predicted for the decades out to 2050.
This Fig 2 eye grabber of a map (click on for full size)
purports to demonstrate that, "..the greater
Melbourne Region has had its lowest rainfall on record compared to all
other periods of similar length. Source: Australian Bureau of
Meteorology." The period chosen by the BoM was 92
months, from Oct 1996 to May 2004, (ask them why). Wondering how
true this BoM/CSIRO statement was I examined the BoM High Quality
rainfall data closest to Melbourne, Yan Yean with data from Jan
1863. See graphic of Yan Yean monthly rain and 92 month average
trend in blue below. ( In 2000 I told Melbourne Water that
they were making unjustifiable claims about "the worst drought in Melbournes history". )
|Clearly the blue 92
month averaged trend at left (click for larger copy) shows the BoM
statement to be false because several periods in our past
show lower values for the 92 month averaged trend. In fact a total of 160 months centred
in the following periods 1867, 1879-1881, mid-late 1890's, and
1940's all have 92
month averaged rain below the value for Oct 1996 to May 2004.
The upshot is that the 7 years and 8 months period (chosen by the BoM) looks to be NORMAL for a dryer phase of the ever fluctuating, cyclic rainfall patterns in the Melbourne region . In 2004 I said Melbourne was experiencing a cyclic dry spell, see below. It is also notable that the Oct 1996 to May 2004 period chosen by the BoM marks EXACTLY a reversal point for the blue trend. Well chosen indeed. Assuming Melbourne Water have paid CSIRO for this study, they should ask for their money back and the report should be pulped. The BoM experts on long term rainfall should carry out a study into Melbourne Region and catchments long term rain trends with all data involved being made available on their web site. Nothing less is adequate with an issue as important as our water supply.
|CSIRO diagram of climate model trends
These trends may look convincing to non-scientist politicians but a comparison to real world data history shows they look very unlikely to come to pass in the decades ahead.
It is my understanding that the rapidly warming model trend for daytime temperatures stems in part from tweaking data with technical corrections that I believe would not stand up to detailed scrutiny.
In my frank opinion this type of modelling will be an unreliable guide to future trends.
||Obviously the CSIRO rain trend must take in data
from much lower rainfall areas than those near the NSW - Victoria
border. All rainfall data on this page, both the Melbourne region
and these stations from north Victoria plus Deniliquin are from the
Bureau of Meteorology (BoM) high quality dataset, of approximately 370
stations Australia-wide. I have only used data extending to 2003
and the rare missing year
has been interpolated. I would have thought that a White Paper on
water resources would have as a cornerstone a peer reviewed paper
at all rainfall records for the region involved.