Friday, November 9, 2012

Mildura Fire Risk - Not Hot off the press, not hotter, not drier

Updated below with a comparison of Mean days above 40 degrees for Mildura. Guess which era is higher?

Must be a slow news day. ABC report today under the somewhat startling headline "Study reveals 'increasing' Mildura fire risk" news of a study that was apparently first published online in April this year (see below). It seems this news is only half a year late, but as it's a "scary" climate change story I guess it's always worthwhile for ABC's activist reporters to get that scary catastrophist climate climate message out; no matter how old! I say apparently because thanks to ABC's extraordinarily "high" reporting standards no where in its brief report does the ABC name the study's title or apparently its authors. It does however have a scary quote from climate alarmist David Karoly. This appears to take the results of the study out of context, for the last line of the abstract of the study reads: "Although these trends are consistent with projected impacts of climate change on FFDI, this study cannot separate the influence of climate change, if any, with that of natural variability. "

In the article Karoly is reported saying: "It gets more extreme in Mildura, and I mean most people in Mildura know that yes it's been getting hotter, it's also been getting drier," he said.
This is used to suggest that there is an increase in risk. And that might be the case if you only look at recent data. If you take a longer view and the data is there for all to see. It seems a different story emerges.
So Hotter and Drier???

Hotter? Here's a compilation of Max temp data from the BOM website based on stations 76077 and 76031 extending from 1910 to 2010, they are combined at the same scale (there does not appear to be a continuously monitored site). 76077 is the post office,  76031 is at the airport about 15 km away). Note that the Max temperature for the period 1910-1940 (red) is higher than 1950-2010. So David, no it's actually not hotter over the long term! It seems that it was hotter overall, earlier last century.

Drier? The figure below is a compilation of rainfall from the same stations. Not that hard to spot the gap between the two, but if you look closely (you might have to click on the figure to enlarge) the mean over the period 1910-1940 (red line -266.6mm) is well below the mean over the period 1950-2010-293.1mm), so no David, not actually drier either, in fact overall, things were drier earlier last century.

The actual figures?: (updated to show figures from 1910)

Drier? From BOM: 
Mean Rainfall station 76077 1889-1949: 266.6mm
Mean Rainfall station 76031 1946-2011: 293.1mm

Hotter? From BOM 
Mean Max temp station 76077 1889-1949: 24.6 degrees C
(Note Mean Max Temp 1910-1949: 24.1 degrees C)
Mean Max temp station 76031 1946-2011: 23.8 degrees C

Mean Min temp station 76077 1889-1949: 10.4 degrees C
(Note Mean Max Temp 1910-1949: 10.5 degrees C)
Mean Min temp station 76031 1946-2011: 10.3 degrees C

Why 1910? according to BOM "Temperature data prior to 1910 should be used with extreme caution as many stations prior to that date used non-standard shelters." That is many sttaions were not yet equiped with the Stevenson Screens that would become standard. Reports from the Adelaide Register in the NLA's newspaper archive suggests a Stevenson Screen was at the Mildura PO in at least 17 January 1907

So given the climate was hotter and drier earlier last century I guess with respect to bushfires it was also riskier! So the elevator report actually is: Risk of bushfires in Mildura may return to levels last seen early last century!
Update: Here's a comparison thanks to BOM of days over 40 degrees between the Post Office site (76077-1889-1949) and the airport (76031-1946-2011). Once again when looking at long term trends the earlier data shows considerably more extreme weather:

When you mistakenly employ activists for reporters I guess it's fair to expect propaganda for news. 

Thanks to ABC's poor reporting we assume (and prepare to wear egg on our face) that this is the paper in question, not that it changes the issues with Karoly's alarmist take on the weather:

  1. Hamish Clarke1,2,*
  2. Christopher Lucas3,
  3. Peter Smith1
Article first published online: 11 APR 2012
DOI: 10.1002/joc.3480

Unfortunately access to more than the abstract requires a subscription, but here's the abstract:


A data set of observed fire weather in Australia from 1973–2010 is analysed for trends using the McArthur Forest Fire Danger Index (FFDI). Annual cumulative FFDI, which integrates daily fire weather across the year, increased significantly at 16 of 38 stations. Annual 90th percentile FFDI increased significantly at 24 stations over the same period. None of the stations examined recorded a significant decrease in FFDI. There is an overall bias in the number of significant increases towards the southeast of the continent, while the largest trends occur in the interior of the continent and the smallest occur near the coast. The largest increases in seasonal FFDI occurred during spring and autumn, although with different spatial patterns, while summer recorded the fewest significant trends. These trends suggest increased fire weather conditions at many locations across Australia, due to both increased magnitude of FFDI and a lengthened fire season. Although these trends are consistent with projected impacts of climate change on FFDI, this study cannot separate the influence of climate change, if any, with that of natural variability. 

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