ABC Catalyst TV show warped view of SW West Australian rainfall

Quote from Catalyst: Mark Horstman
“Since the 1970s, the south-western corner of Western Australia has suffered a dramatic decline in their winter rainfall, so rapid and so extreme that it’s like, somewhere, a giant tap is being turned off.”
What utter exaggerated twaddle.
Once again the Australian media spins normal climate variations as something caused by IPCC climate change.
The entire thrust of the show is that rainfall in “..the south-western corner of Western Australia..” dropped ~15% in the 1970′s and a scientist is quoted linking this to changes in Antarctic ice cores. The scientist – Dr Tas van Ommen
Principal Research Scientist, Ice Cores and Climate, Australian Antarctic Division, Hobart – may well be right is linking the events – we will look for a peer reviewed paper on the subject.
My point is that there are many sudden rainfall change events in Australian climate history – and from larger regions than SW WA – and little attention is put into explaining these.
Lets take two examples from the BoM online “Timeseries – Australian Climate Variability and Change”.
Here is a graphic of West Australian rainfall – note the sharp increase in the 1990′s – what caused that ?
Here is a graphic of Murray Darling Basin rainfall – note the sharp increase in the 1940′s – what caused that ?
You can explore the BoM data for NSW etc and that huge increase in rain about 1950 often stands out. But it is a feature that nobody wants to explain.
Maybe because it corresponds with the period of post WWII cloud seeding experiments. Sorry – not PC.
Note my graphic of Perth dam catchment rain – steady over 35 years.
Finally a graphic of Perth rain history back to 1876 – note how the pre WWI winter rain is similar to the post 1970′s rain. Who is to say what is “normal” ? I am not aware of any “tablet of stone” which tells us whether the WWI to mid 1970′s high rain era was normal – or are the slightly dryer decades before and after more “normal”.

3 comments to ABC Catalyst TV show warped view of SW West Australian rainfall

  • pattoh

    Warwick
    The thing which galled me the most was that the 750year time span for the ice core just ever so conveniently missed the MWP. I am sure it was not deliberate. Perhaps there core drill just happened to break down at a point where the data did not fit the argument.

  • Tas

    Warwick –

    re your comment:
    ” we will look for a peer reviewed paper on the subject”

    I can help: the work is published in Nature Geoscience and a link to PDF can be found on the www.abc.net.au/catalyst/stories/2929759.htm
    Catalyst webpage for this story.

    re Pattoh:
    Don’t be galled – analysing the core is an exacting task in the laboratory and time consuming in data processing. The core will eventually provide this sort of information over a couple of thousand years or more and we are as interested as anyone in learning everything we can. The question of how widespread the MWP was, globally speaking, is still a very open issue. There are good reasons to think that if it did extend beyond the Northern Hemisphere it may well have involved the ocean overturning circulation transporting more heat northward. Then the signature in the south would be a cooling! The associated impact on moisture transport (and hence rain/drought) is not obvious. Getting robust data on past changes is the best way of testing/building our understanding and it is what drives our work.

  • Romanoz

    Looked at the SCAR Report for 2009. This is a beatup, similar to the previous one on the Antarctic which speculated on the possibility of the ice cap “floating off” because the land mass is below sea level? There have been unexplained variablity in rainfall in the SW over the last 1000 years!

    There is a strong relationship(in SW Australia) between winter rainfall, the phase of the SAM and the circumpolar longwave circulation pattern …The work in progress indicates that southwest Western Australia experienced periods of higher mean winter rainfall, with high interdecadal variability during 1300 to 1600 AD, followed by lower mean but less variable winter rainfall from 1600 to 1900 AD, which is similar to the past 50 years (Goodwin, in prep.)…
    The exception is a climate change event (a cooling event)
    commencing ~AD 1700 and ending by ~AD 1850, during which circulation and temperature
    acted synchronously.

    Into this brew, they throw increasing CO2 and the ozone hole and come up with the old
    cum hoc ergo propter hoc fallacy.

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