More on rainfall

For those unconvinced about my previous claim that, according to the BOM data, there doesn’t appear to be a drying trend on the east coast and think it might be an artifice of too broad averaging, I note that they should have a look at the trend maps found here. For example the rainfall trends from from 1900 to 2006.
Australian Rainfall trend 1900 - 2006

This shows few regions which have shown a definite drying trend over the period. One clear exception being the south west of WA, which does show a drying trend over pretty much anytime period you pick. In addition it appears that some slight trend could be evident in mid to northern Queensland.

Go and have a look at some of the different time periods on their site, the lack of a clear trend for much of eastern Australia isn’t just for the period 1900-2006. In case any one’s concerned that its because we started the comparison in a drought. Take 1910-2006, 1920-2006 or 1930-2006 and you get something similar.

Indeed its not unless you compare with the 1950’s to 1970’s that you get a really marked decrease in rainfall in most of Eastern Australia.

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4 Responses to More on rainfall

  1. […] Steve Edney expands on a previous post showing that rainfall levels in south-eatsern Australia haven’t in fact fallen over the last century, despite media and politicans’ claims to the contrary.  But Steve seems to ignore the role of higher evaporation levels flowing from higher temperatures.  Nevertheless,  his figures and maps do suggest that current water shortages owe as much to politicians’ failure to build new dams to keep pace with growing population as with global warming. […]

  2. Steve says:

    On this point, its true warmer temperatures will lead to greater evaporation, so I am not trying to refute that there may be water shortages induced by climate change. Nor am I insisting that there will be no change to rainfall with climate change in south eastern Australia in the future. Merely that the historical record shows little evidence for it having already occurred.

    I do however think there has been a tendency to view the high levels of rainfall recieved in the 50’s and 70’s in particular as “normal” and the low rainfall of other periods as abnormal and this has biased our views on what to expect.

    In addition mean rainfall is higher than median rainfall. The big years skew the average upwards. Most years we should expect less than average rainfall.

  3. Steve, after some absence I came back for a visit to your blog and discovered, that we just recently wrote about the same topic “climate”, even though from a complete different viewpoint. I had a look at a climate zone diagram which is hard to decipher if you are colorblind. And when I see you diagram I have the same problem: I don’t really see any difference in the areas. Maybe you would like to try Protan Tools (see my article: Color Translation — Readable Diagrams for the Colorblind), which makes the diagram definitely more readable to me.
    By the way, my blog Colblindor has now its own url. Maybe you like to update your blog link list. – Daniel

  4. Steve says:

    Ok Thanks Daniel. I haven’t written anything about colourblindness for a while. This graph though is very very hard for me to interpret, but due to the slightly darker line denoting the border of dry and wet I can work it out.

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