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Tuesday, January 11, 2011

Under Brisbane Waters?

I have been holding of blogging on the Queensland floods for a week or so, now.  I thought I might wait for a more appropriate time.  This seems like an appropriate time:

Brave New Climate - Qld Floods Highlight the cost of climate extremes (Link added 14/1)

To put that in context, that is just one of many spectacular videos from yesterday's flash flood in Toowoomba.  Toowoomba lies in a broad, very flat valley at the top of a range.  The catchment area for the flood was just Toowoomba itself.  Despite this it rained sufficiently fast to generate a flash flood capable of sweeping cars away, and in one instance drive a car down a drain hole.

At the bottom of the range, the flooding was much worse.  A wall of water 8 meters high descended on the residents of the Lockyer valley, with no warning, trapping lucky residents on their roof tops and unlucky ones in their cars or without shelter.  One car was spotted floating in the middle of the flood with a family inside, but by the time a rescue could be organised, it has floated away and lost.  The known death toll stands at eight people, and over seventy two people are known to be missing.

The flood water is now making its way down the Brisbane River system at depths predicted to peak just  two meters less than the highest flood of the last century (1974) if there is no more rain.  The downpour continues.

Of course, and even larger perspective is needed.  In March, 2010, Queensland experienced record breaking floods, with many towns experiencing record flood depths, and the greatest area flooded ever reported for Queensland.  It was reported that the flood effected area in March was larger than Victoria (area: 240,000 square kilometers, or 92,000 square miles).  In the week after Christmas, that record was broken, with a reported flooded extent greater in area than New South Wales (810,000 square kilometers or 313,000 square miles).  That is an area about the size of the five largest contiguous US states either under water or cut off, or with crops rotting in the ground two weeks before harvest.

In the last week of December, the floods were mostly confined to the interior behind Rockhampton and Bundaberg (also flooded) and to the Darling Downs and interior.  There was minor flooding in Brisbane, and in the north of the state (where at least one woman lost her life).  Since then the floods have moved south, flooding Gympie, Maryborough, and of course, Toowoomba and the Lockyer Valley (and soon to be Ipswich and Brisbane).  Dalby deserves a special mention, having experience five flood peaks in two weeks.

As of the end of December the economic toll was massive, with an estimated 6 billion dollar loss in damage to roads, infrastructure and crops.  I have not heard more recent estimates as the news services and government have been overwhelmed just reporting the human dimension of the disaster.  A larger economic loss will probably (and ironically) come from the coal mines behind Rockhampton which are unable to operate and unable to deliver coal to the ports, and do not expect to be able to for at lest three months - weather permitting.

The weather, which may or may not permit, is driven by the current La Nina which is expected to last for another three months.  This flood crisis is likely to be an ongoing disaster.  It certainly will be as the inland floods slowly roll down towards the Murray, giving NSW towns the joy of flood peaks they can anticipate up to a month in advance as they see the water work its way down the Murray's tributaries.

And now Global Warming rears its ugly head.

Yes, this flood is evidence of Global Warming, but only in a very week way.  Increased flood levels have been a predicted consequence of Global Warming for some time now, with the CSIRO predicting a 10 to 20% increase in peak rainfall for extreme weather events even for less than 1 degree increase in temperatures, and a doubling of flooded areas for a 1 degree increase.  If a theory predicts something, then its occurrence is evidence in favour of that theory.   But most events are predicted by many theories, and just because it is evidence for one theory does not mean it is not stronger evidence for another.  So, yes this is evidence for Global Warming; but this event could have happened without Global Warming.  So it is not strong enough evidence that anyone should change their view of Global Warming based on it.

So why then do I mention Global Warming?

The simple fact is that human sourced carbon dioxide is warming the planet, and floods like this are expected to be the norm for Queensland by mid century as a result.  In fact the pattern of extended and intensive drought (as experience by Queensland for approximately 10 years prior to November of 2009) followed by extensive and catastrophic floods  are going to become common place.

Australia has always been a place of extremes, of "droughts and flooding rains", but it is going to be more so.  The current Queensland (and now New South Wales) floods are a disaster beyond anything experienced in Queensland before - but in the coming century we can expect its like every ten years or so.

Additional reading (added 16:49, 12/01/11):
Watching the Deniers - climate change predictions
Watching the Deniers - Andrew Bolt gets it very wrong
Skeptical Science - Brisbane Floods
Hot Topic - Too Many Teardrops


  1. Tom,
    The records show that the FLOOD PLAINS that people built on have had worse floods every few centuries or so, and lesser floods every few decades. In addition, dams were not built or built but not properly used by the government. There is no evidence to relate either the droughts or floods to other than normal variation. You seem to be sure that CAGW is happening, and I do not. You can claim anything you want, but without sufficient support, you are purely speculating.

    I am very sorry for the deaths and misery, but the basic problem is people building on known FLOOD PLAINS without any defensive infrastructure being included.

  2. Leondard, my responce can be found in my new post. It has a bit of bite because I consider your remarks not only ill considered, but offensive (particularly your final comment), although I have seen other ill considered comments by opponents of AGW.