UPDATE: Thanks to a reader who pointed out where to find the 2008 version of BOM rainfall data, I’m able to plot the two data sets. There are differences. See addendum below. – Anthony
BOM loses rainfall
by Tom Quirk on Quadrant Online
Shock Murray-Darling Basin discovery
Analysts at the Australian Bureau of Meteorology have some explaining to do.
In the last two years some 900 mm of rainfall have been removed from the rainfall record of the Murray-Darling Basin. This startling discovery was made by comparing the annual Murray-Darling Basin rainfall reported on the Bureau of Meteorology website in August 2008 and the same report found yesterday.
The annual rainfall figures are shown as reported in October 2010:
Yearly rainfall in the Murray-Darling Basin from 1900 to 2009 as reported in October 2010 with a mean value of 467 mm (solid line).
There is no significant trend in rainfall through this period but there is large variability with rainfall extremes of a 257 mm minimum and a 787 mm maximum.
The comparison with the August 2008 report is revealing. The difference is a decrease of 900 mm rainfall in the 2010 report. The significant decrease occurs after 1948:
Changes to Bureau of Meteorology record of Murray-Darling Basin rainfall. Data downloaded August 2008 and October 2010
The Bureau is already on record adjusting Australian temperature measurements and they now appear to have turned to rainfall, making the last 60 years drier than previously reported.
One can understand that adjustments might be made to a few of the most recent years as records are brought up to date but a delay of forty or fifty years seems a little long.
This raises the question how certain is the data that is used by policy makers?
When we are confronted by apparently definitive forecasts of our future with rising temperatures and less rain, are we living through a period that brings to mind the Polish radio announcement of Soviet times?:
The future is certain only the past is unpredictable.
WUWT Reader Charlie A writes:
The Wayback machine comes to the rescue!
http://web.archive.org/web/*/http://www.bom.gov.au/web01/ncc/www/cli_chg/timeseries/rain/0112/mdb/latest.txt is the Murray Darling basin annual rainfall archived by archive.org on January 30th, 2008.
The current series can be found at http://www.bom.gov.au/web01/ncc/www/cli_chg/timeseries/rain/0112/mdb/latest.txt
The query form for data and graphs is at http://www.bom.gov.au/cgi-bin/climate/change/timeseries.cgi?graph=rain&area=mdb&season=0112&ave_yr=0
So, now having the older data, I decided to run a quick plot to see the difference. I fired up my Dplot program and came up with this in about a minute:
There are differences in the two data sets. The 2010 data has lower values, starting around 1950, just like the Quadrant article. WUWT?
Addendum: I notice the peaks post 1950 seem to be reduced, but the lows are not. Strange.