‘I’m Worried’: Twin Concerns of Climate Drivers May Cause El Niño to Reset

Anyone with a passing knowledge of the weather knows that last week the Bureau of Meteorology announced that El Nino had begun.

But somewhat lost in the flurry of El Nino announcements was another warning.

Meteorologists have noted that Australia's “other” El Nino, a similar but separate climate driver, is occurring at the same time.

And this double whammy of climate can amplify their overall effect.

A recent spell of unseasonably warm weather in the East, just weeks after the end of winter, may just be the beginning.

Former NSW Fire and Rescue Commissioner Greg Mullins summed it up when he spoke BBC last week.

“Forestfires will be back in the headlines,” he said. “I'm nervous.”

A meteorologist told news.com.au that 2023 could be “very dangerous” and while it is unlikely to be as bad as 2019's Black Summer, it may not be far off.

With El Nino completely gone, eastern and southern Australia in particular can expect less rainfall and hotter days and nights in the coming months.

The occurrence of heat waves is also higher and the risk of bushfires increases.

The last El Nino was in 2016. They usually last through spring and summer until fall. But they can return for several years. This El Nino will peak in January – due to high summer.

Enter the IOD

But this time, El Nino isn't the only climate driver in town. It bubbles up just as the Indian Ocean Dipole (IOD) is in its positive phase.

“Having a positive IOD and El Nino join forces increases the chances of drier weather across much of the country, especially inland regions.” Sky News Weather Meteorologist Rob Sharp told news.com.au about it.

“Positive IOD events particularly increase the heat in the last few months of the year in these regions – just as we saw in 2019, when we last saw a positive IOD.”

While El Ninos mainly affect eastern Australia, the IOD also affects central and southern Australia, potentially adding to the pain.

“South Australia, Victoria, Tasmania and New South Wales all experience significant impacts from both El Nino and positive IOD events – both of which reinforce the warming and drying trend for most of these regions,” Mr Sharp said.

“The worst black summer since”

Worryingly, one of Australia's worst fire seasons – the Black Summer of 2019 – was positive during the IOD event. It killed 34 people and destroyed more than 3000 buildings.

And that was without the added oomph of El Niño. This summer will have both.

However, most weather watchers suspect that the summer of 2023/24 will be as disastrous for bushfires as 2019.

They note that 2019 follows a number of years in which Australia has broken up. Right now, Australia has just emerged from a three-year wet spell of La Nina.

But that doesn't mean Australia can rest – not a long-term host.

“I'm not a betting man, but if I were, I'd say we're going to have a lot of fires this year,” Mr Mullins, who is the founder of Emergency Leaders for Climate Action, a former bushfire group. SES chiefs, who are lobbying for stronger climate change policy, said in July.

“Not like a black summer, but periodically we will have days, maybe several days in a row, where we lose homes.”

Sky's Mr Sharpe agreed that the cause for concern was high fuel loads in some areas which were already drying up.
“The fire season now underway across much of the North and East can be very dangerous. “At this stage we think it will be the worst since the Black Summer, but likely to fall short of its scale,” Mr Sharp said.

“As I said, it only takes one big fire to cause a disaster – as we saw in Maui.”

The last positive IOD coincided with El Niño in 2015. It became Australia's fifth warmest year on record – a feat it has since surpassed.

The climate measure included Australia The warmest October in history.

But the rainfall was only slightly below average, which shows that you can't completely predict what the different climate factors will do.

How El Niño and the IOD work

So what mechanisms are really at work when we talk about El Nino and the Indian Ocean Dipole?

The first thing to note is that they are essentially the same phenomena.

This climate driver is a measure of the interaction of winds and water. The difference is that El Nino is in the Pacific Ocean and the IOD is in the Indian Ocean.

El Nino – Spanish for “little boy” – is the name given to one extreme of the El Nino Southern Oscillation, or ENSO. At the other extreme of ENSO is La Nina, or “Little Girl.”

It's a natural cycle that runs between El Nino and La Nina, but exactly when it changes and how strong it gets varies.

Most metrological organizations measure ENSO by sea surface temperature. El Nino is declared when waters in the Pacific Ocean area are 0.5 degrees above average.

That measure was reached months ago, prompting the US National Oceanic and Atmospheric Administration to declare an El Niño in July.

But BOM is stricter. Not only does he want to see the water temperature rise to 0.8C above average, he also wants to link it to a specific measure of atmospheric pressure.

It just happened recently.

El Nino has been officially declared in Australia

When ENSO is neutral – between La Nina and El Nino – trade winds blow from east to west, pushing warmer waters towards Australia, which helps cloud formation and average spring and summer rain in the east of the country.

When El Nino takes effect, these trade winds can weaken or reverse. Less warm water reaches us, so there are fewer clouds – and that can stop precipitation.

The BOM predicted that sea temperatures could peak in January at 2.8C above normal.

IOD also refers to wind and water. In a positive phase, as now, warm waters are closer to Africa, which contributes to precipitation in the east of this continent and takes it away from Australia.

Positive IODs do not last as long as El Ninos. In the spring it is affected, but it usually ends in the summer when the north monsoon arrives.

The formation of this year's El Nino is good news for parts of East Africa and the Americas, where rainfall is expected to be needed.

But for Australia, with the double whammy of El Nino and IOD, a scorching summer and all the risks that can bring.

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