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Extreme Rainfall Trends In Australia

October 14, 2016
tags:

By Paul Homewood 

 

As promised, a look at the Australian climate extremes graphs for precipitation, as presented by the BOM.

Most of the extreme rainfall graphs show a similar pattern, so I have picked this one, defined as “Annual total precipitation when daily precipitation > 99th percentile”.

This, in theory, takes account of varying rainfall expectations from region to region, as the BOM explain:

 

Extreme climate events such as heat waves, cold snaps, floods and dry spells have significant impacts on society. To examine whether such extremes have changed over time a variety of extreme climate indices can be defined, such as the number of days per year which exceed, or fail to exceed, fixed thresholds. However, since people tend to adapt to their local climate, a threshold considered extreme in one part of Australia could be considered quite normal in another. To overcome this problem, thresholds based on percentile values can also be defined.

 

R99p.18824

http://www.bom.gov.au/climate/change/index.shtml#tabs=Tracker&tracker=extremes-timeseries&tQ=graph%3DR99p%26ave_yr%3D0

 

What the data shows is that extreme rainfall has not become more common or intense in recent years. Indeed, the opposite looks to be the case.

This may be slightly surprising, given that total rainfall in Australia has noticeably increased since prior to 1970.

 

rranom.aus.0112.55474

http://www.bom.gov.au/climate/change/index.shtml#tabs=Tracker&tracker=timeseries&tQ=graph%3Drranom%26area%3Daus%26season%3D0112%26ave_yr%3D0

 

 

At the other end of the scale, we have the average number of consecutive dry days, the maximum number of consecutive days with daily precipitation < 1 mm.

We can see that this index has been running at record low levels in the last decade or so.

 

CDDs.59772

http://www.bom.gov.au/climate/change/index.shtml#tabs=Tracker&tracker=extremes-timeseries&tQ=graph%3DCDDs%26ave_yr%3D10

 

To sum up:

1) Rainfall is not becoming more extreme.

2) Dry spells are becoming less common.

 

We already seen that the extreme temperature graphs show that very hot days are not getting hotter or more frequent in Australia. Instead, it is the very cold ones that have become less common.

In other words, climate is not getting more extreme in Australia. If anything, the reverse is true.

We are often told that global warming is leading to more extreme weather. Not for the first time, the facts tell a different story.

5 Comments leave one →
  1. October 14, 2016 4:05 pm

    It seems that weather is very variable everywhere and that showing trends is more sophistry than science.

  2. October 14, 2016 6:11 pm

    The same increasing weather extremes argument was made in Chapter 1 of the 2014 US National Climate Assessment. I was able to debunk every single one of the examples using readily available US historical data. Essay Credibility Conundrums in ebook Blowing Smoke. Drought, flood, heatwave, rainfall, blizzards, tornados, …

  3. October 14, 2016 6:17 pm

    By chance or not, it’s just been the wettest September on record in large parts of Australia.

    Australia in September 2016
    http://www.bom.gov.au/climate/current/month/aus/summary.shtml

    [This link will point to another month in due course]

  4. Matt permalink
    October 15, 2016 11:01 am

    ‘Extreme climate events’ – otherwise known as weather!

  5. October 17, 2016 11:13 am

    Reblogged this on ajmarciniak.

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