By Nick

August to October rainfall in 2010. Blue = wet! Image from BOM.

As a visitor to these shores I feel fairly cheated by the weather. I arrived almost exactly two years ago, just as La Nina was really getting going. And how it rained. The first kangaroos I ever saw where sheltering underneath a tree looking very bedraggled. A very convincing way to break a national stereotype I will grant you, but did the rain really have to last for two years?

The Bureau of Meteorology have just released a booklet on the 2010-2012 La Nina event, which explains in fantastic clarity, what exactly happened to the oceans and atmosphere that caused Australia to receive so much rain, a god-send to some, and a burden to many others. OnCirculation’s guide to ENSO is pretty good too!.

You can download it here: http://www.bom.gov.au/climate/enso/history/La-Nina-2010-12.pdf

So where too from here?

As a great believer of what is known as the spring impermeability barrier – the idea that it is statistically impossible to predict an ENSO event until the (Northern Hemisphere) summer – I think now is the time to put away wild conjecture and can start to look forward to what this year might bring. Thankfully it looks like the more neutral conditions that started in April will continue for the next six months. Some indicators have already got us going back into El Nino conditions, while others remain neutral. Climate models can’t agree which side of the man-made threshold we will be on regarding neutral or El Nino conditions – so it looks like slightly warm neutral conditions will prevail or even a weak El Nino event. (Data from http://www.bom.gov.au/climate/enso/ who give a great little synopsis every couple of weeks).

As for the long term and the consequences of climate change, the models are currently undecided as to what future scenarios are likely to happen under increased global temperatures. Some say more El Nino like conditions and some more La Nina like conditions. One thing that is being established is that even if the average conditions shift one way or the other, the variability and swings between the two states will remain. The idea that we might head towards, say, more El Nino like conditions is misleading, because it gives the impression that La Nina’s won’t happen, which they most likely will.

In fact, we may already be seeing the impacts of greater variability in the system. A paper last year by Janice Lough at the Australian Institute of Marine Sciences in Townsville suggests that we might already be seeing more frequent swings between the two extreme states of ENSO. Queensland looks set to find itself trapped in an increasing cycle of droughts and floods. Not particularly ideal. It seems to be yet another case of an increase in extreme weather conditions resulting from climate change.