La Niña has hammered eastern Australia during the last couple of summers. Across Queensland and NSW, so many communities have experienced unprecedented flooding. So in this Squiz Shortcut, we get you across a few of the different weather systems affecting Oz, what climate change has to do with it, and what it means for Aussies going forward.

Far out it’s been wet in some parts of Oz…
It sure has, and it’s largely thanks to La Niña. It’s a weather system that’s associated with above-average rainfall, cooler daytime temperatures for areas south of the tropics, and a greater chance of tropical cyclones.

So it brings a lot of rain?
It does. La Niña also has a lot to do with wind – specifically, the trade winds that blow east to west near the equator in our neighbourhood. When that wind speed picks up, it changes the ocean current by drawing up colder water from the depths of the Pacific Ocean – and warmer water is pushed west towards Australia.

What does that have to do with rain?
The warmer the ocean, the greater the chance of rain because it evaporates more quickly. That condenses into clouds and then the rains come.

I’m following you… What does the term La Niña actually mean?
It’s a Spanish word that means ‘the girl’. And she has a sibling called ‘El Niño’, which means the boy.

So what’s El Niño?
It’s associated with dry conditions and drought. As it’s been raining and cool here, South America has been hit by soaring high temperatures and a dry spell that’s wreaking havoc on its agricultural sector, just as it did here in Oz during our long and painful drought lasted until the end of 2019.

How are La Niña and El Niño connected?
Broadly speaking, they’re part of the same weather pattern called the El-Niño-Southern Oscillation system – or ENSO. That pattern helps us understand the weather events occurring on Australia’s east coast.

What about our west coast?
What happens there is driven by another weather system. The ocean off the West Australian coast is the Indian Ocean, so the weather system it’s guided by is imaginatively called the Indian Ocean Dipole.

What’s that about?
The Indian Ocean Dipole is defined by the difference in sea surface temperatures between 2 areas, or poles.

Ah, hence the ‘dipole’ reference?
Ding ding ding… One of the poles is in the Arabian Sea in the western Indian Ocean and an eastern pole in the Eastern Indian Ocean south of Indonesia.

So how has that been affecting the weather in Western Oz of late?
Well, in July last year, the weather bureau declared that for the first time in 5 years, the Indian Ocean Dipole went into a ‘negative’ phase. That tipped the odds towards a wetter-than-average spring just gone. But the weather bureau says that’s now switched back to ‘neutral’.

Any other terms I need to know?
I can’t tell whether you’re being sarcastic or not, but yes… The final weather system to note is the Southern Annular Mode – or SAM. Basically, when it’s positive – like it is at the moment – the winds blow onshore, which increases moisture and rain to Australia’s south.

So our big weather system have been set to ‘wet’?
Yep. Summers in Australia are normally moist, but this year the combination of La Niña, a negative Indian Ocean Dipole, plus the positive Southern Annular Mode have proven to be a soggy trio.

What does this all have to do with climate change?
Well, to start off, the conversation about weather systems isn’t a proxy for climate change. That’s because weather differs from climate.

How so?
Climate change is about long-term and sustained shifts in temperatures and weather patterns. Some of those shifts may be natural, like through changes that occur to the sun’s activity.

But most of it is due to us humans?
That’s right. Since the 1800s, human activities have been the main driver of climate change, primarily due to burning fossil fuels like coal, oil and gas through industries including energy, agriculture and transport that contribute heavily to greenhouse gas emissions.

What’s the latest on where the world is at on climate change?
The United Nation’s Intergovernmental Panel on Climate Change released its latest assessment in February. It said that the world has already heated by 1.1C and predicted that current policies puts us on track for at least 2.1C warming by 2100.

That’s not good…
No. That’s why there are growing calls to implement more aggressive policies now in order to limit the global temperature rise to 1.5C. It’s that sort of level where the experts say the worst consequences of global warming can be limited.

Which are?
For one thing, more extreme weather events. That’s because a warmer atmosphere contains more moisture, and it will see rainfall extremes become more frequent and intense.

So what’s the link between climate change and the weather systems like La Niña?
What the experts say is extreme El Niño and La Niña events may increase in frequency from about one every 20 years to one every 10 years by the end of this century. 

Geez… So more extreme events like the recent floods?
That’s the prediction. Which is a big concern given the risk to lives, the massive upending of people’s homes and businesses, and the huge costs. 

How expensive will the recent floods be?
Early estimates say the bill will be about $2.2 billion, and the Insurance Council warns that will rise as more people get their claims assessed. 

So what’s the plan for next time, then?
This is where we get to some very difficult questions… The Insurance Council says that 2-3% of Aussie homes are located in frequent flood zones, so it’s calling on governments to commit more than $2 billion over the next 5 years to make communities more resilient.

How has the federal government responded?
Its disaster recovery agency headed by former NT Chief Minister Shane Stone gets that there is a problem… He says taxpayers can’t continue to pick up the bill and Aussies have to have an “honest conversation about where and how people build homes”. 

So what are they going to do?
Some residents of flood-affected the recently flooded areas have been asked that question and they have been very clear that they can’t afford to move to a new area. So one solution that has been proposed is relocating entire communities from flood zones with government assistance.

You can’t move towns and cities… 
Yes, you can. 

No, you can’t. 
It’s something that has been done as recently as 2011…

What? Where?
Grantham in Queensland’s Lockyer Valley. Twelve people died in the town of after it was inundated by floodwaters in 2011. The mayor was an American environmental engineer and he put together a plan called the ‘Grantham land swap’. Land on top of a hill was gazetted for new homes. It took 11 months and cost the federal and Queensland governments $18 million to move 90 families to higher ground.

That’s not on the same scale as moving a city like Lismore…
No, but it’s interesting nonetheless. And it has become an international example of how to move a town that’s susceptible to natural disasters.

Geez there are some tough decisions coming up… 
There sure are. 

Squiz recommends:

The Australian Academy of Science website

Interview with a 93yo woman who had an incredible escape from her flood-ravaged home – 7News