El Niño is back, here’s what to expect

Sam Hawley: Hi, I’m Sam Hawley, coming to you from Gadigal Land, this is ABC News Daily. It’s official, the world is back in an El Niño event. You won’t have noticed it just yet, but historically, it means we’re heading for a very hot and dry period. Today, a climate scientist steps us through why it’s happening and what we can expect.

Nandini Ramesh: Hi, I’m Nandini Ramesh. I’m a climate scientist with CSIRO and the University of Sydney.

Sam Hawley: Nandini scientists are warning the world is heading into unchartered territory. That does not sound very good.

Nandini Ramesh: No, it does not. I understand your alarm. Yes. So what’s happened now is that we’ve had the warmest day on record in terms of the global average temperature. So even though it’s winter here, the northern hemisphere has been so hot that we’ve gone past the historical record for the warmest day ever.

Nick Grimm: On Monday, the average global temperature ticked just over 17°C, the hottest average ever. While ocean temperature…

Reporter: Texas is entering its third week of a record breaking heat wave. The heat index could top 120 degrees.

Nandini Ramesh: And that’s because we’ve been warming the planet with our greenhouse gas emissions. So the temperature has been ticking steadily upwards and.

Sam Hawley: The World Meteorological Organisation, it’s actually declared an El Niño event, hasn’t it?

Nandini Ramesh: Yes, that’s right.

Sally Sara: It’s been widely anticipated, but now it’s official. El Niño is back with the weather pattern expected to bring hotter and drier conditions.

Nandini Ramesh: So for the last three years, we’ve been in a state of La Niña. And during a la Niña, you typically get cooler temperatures over the tropical Pacific. And now that we’re going into an El Niño this year, this means we’re getting warmer sea surface temperatures over the area between about Peru and the dateline. So right in the equatorial Pacific. So it’s become warm enough that certain organisations have declared it an El Niño. And what this has to do with the global average temperature is that during El Niño events you get a release of heat stored in the ocean to the atmosphere, so you get a warming of the atmosphere temporarily every time you get an El Niño event. So for example, the last time we had a really big El Niño event was 2015. 16 and 2016 is the hottest year on record.

Sam Hawley: Wow. And I can see a WMO official is warning over the next five years we could actually break records again.

Professor Petteri Taalas, WMO secretary-general : What we know is that throughout the next five years, we are likely to have one of the warmest year on record.

Nandini Ramesh: That’s right. And this El Niño event that is developing is likely to affect the temperatures the most in 2024. When you get an El Niño event, it’s typically the second year of the El Niño that sees higher temperatures. So in the past, for example, we had an El Niño during 2015 to 2016, and 2016 holds the record for the hottest year. And so this time it’s likely to be 2024 as we go into an El Niño over the summer months.

Sam Hawley: So the WMO, that’s the UN body, it’s declared an El Niño, as you say, that’s the first time since 2015, 2016. But our own Bureau of Meteorology, it’s not yet done that it hasn’t declared this event. That’s likely to come, though, isn’t it?

Nandini Ramesh: That’s right. There’s an active El Niño alert, according to the Bureau of Meteorology, and the forecasts are in agreement with the international ones where the models all have quite high confidence that we’re going into an El Niño event over the coming months.

Sam Hawley: Yeah. All right. So let’s now unpack what we can expect, because last year, of course, we spent a lot of time talking about La Niña and we had so much rain and it never stopped raining and it was pretty dreadful.

Reporter: The day of rain left Sydneysiders soggy and slippery. Our third consecutive La Niña has delivered the city its wettest year ever.

Reporter: The wet October is thanks to climate drivers, including a negative Indian Ocean dipole and La Niña pumping moisture into the atmosphere. We had way.

Sam Hawley: Too much rain in some areas, so what can we expect now?

Nandini Ramesh: So El Niño years are typically drier and warmer than usual across much of the country. So the eastern and northern parts of the country have the strongest relationship. And where exactly you are has an impact on that, too. So, for example, an area like the Murray-Darling Basin has a very clear relationship with El Niño and La Niña events, whereas the Eastern seaboard, that is a less strong relationship. There are other factors that are important too, like what’s happening in the Indian Ocean. So there’s a similar phenomenon to El Niño called the Indian Ocean dipole that occurs in the Indian Ocean, and that also has effects on how wet or dry Australia is.

Sam Hawley: Right. So do we know how dry it will get or is that still a real unknown at this point?

Nandini Ramesh: At this point, we don’t necessarily know exactly how dry it’s going to be. The early indicators show that the Indian Ocean dipole is going to reinforce the dryness over Australia. So that’s that’s sort of the early information we have.

Sam Hawley: Nandini, how often have we actually lived through El Niños? Because I do have this very strong memory in the early 2000 of showering with a bucket and using that water on the garden. We were in this really deep, severe drought.

Nandini Ramesh: Of course, yeah.

Sam Hawley: Was that an El Niño?

Nandini Ramesh: So El Niño events happen every 2 to 7 years. So the frequency is not a fixed frequency. The last one we had was quite a small 1 in 20 19 to 2020 and we had a bigger one back in 2015 to 2016. So you can see it’s every few years the period that you’re speaking of in the early 2000s or so is actually the millennium drought, which had a number of different factors associated. So that wasn’t specifically El Niño that was causing that. There were some El Niño events that reinforced that dryness, but it was a number of different factors together at that time.

Sam Hawley: Okay. All right. But we’re obviously heading now into a period of less rain and more heat. And the environmental consequences of that we know are really or can be, of course, really, really bad. We saw, of course, in 2019, 2020, those fires, you know, billions of animals were killed.

Speaker10: Fire crews are battling to prevent two huge bushfires from joining together to form a mega blaze near the Victorian New South Wales border.

Reporter: Wildlife volunteers have begun the grim process of searching for injured animals in fire ravaged regions. It’s estimated hundreds of millions of native animals have already died in this summer’s horror bushfires.

Sam Hawley: So it’s a it’s a serious weather event, isn’t it?

Nandini Ramesh: It can be quite a serious event. One thing that I would caution people about here, though, is that when you see forecasts of a strong El Niño or a moderate El Niño, those qualifiers actually apply to the temperatures that occur in the Pacific Ocean. So that’s not necessarily the same as how strong the effects will be over Australia though. So 2019 to 2020, the example of the bushfires that you just gave that year was actually a very weak El Niño, but we still had these massive impacts. So that relationship is not at all linear with Australian impacts.

Sam Hawley: So how long does an El Niño last?

Nandini Ramesh: So the typical life cycle of an El Niño event is about nine months. They usually get started in the winter months around June, July. And those temperatures out in the Pacific generally peak around December. And then they slowly decline and fizzle out by about March, April the following year.

Sam Hawley: Right. And is this all linked to climate change?

Nandini Ramesh: Well, El Niño and La Niña events are natural cycles. They’ve existed for as long as the Pacific Ocean has existed. And scientists are still working out really, how climate change interacts with those cycles. However, one thing that we do know is that because we have a warmer atmosphere, a lot of the impacts of El Niño and La Niña events are going to be intensified. So, for example, if you just have a warmer baseline because of climate change and then you have a heat wave because of an El Niño event, you’re going to reach higher temperatures and that makes the heat wave more dangerous. Just having that warmer background means that these events are more impactful.

Sam Hawley: So Nandini, what should we expect then in the future? Are these weather events, these extreme weather events, are they going to become more common?

Nandini Ramesh: Well, in terms of the intensity of storms and heat waves, we do know that climate change projections tell us that they are going to get stronger. The frequency of different types of storms might change. I can understand people’s alarm, given the history that we have here in Australia with El Niño events. But I would say that don’t panic. It is important to keep in mind that forecasts of a moderate to strong El Niño don’t mean that the impacts on Australia are going to be extraordinarily large. But El Niño and La Niña will continue to happen and either way we have to be prepared for their effects.

Sam Hawley: Nandini Ramesh is a climate scientist at the CSIRO. The Australian Bureau of Meteorology is expected to declare an El Niño event in coming weeks. This episode was produced by Veronica Apap, Flint Duxfield and Sam Dunn, who also did the mix. Our supervising producer is David Coady. I’m Sam Hawley. You can find all our episodes of the podcast on the ABC Listen app. Thanks for listening.