Following The Bureau of Meteorology announcement that we can expect to move out of the current neutral phase of the El Niño-Southern Oscillation (ENSO). We have been in a neutral phase of ENSO since the “triple dip” of La Niña over three consecutive years ended earlier this year. The Bureau’s recently released El Niño ‘alert’ follows climate model forecasts indicating there is approximately a 70% chance of El Niño forming in 2023.
CSIRO researchers explain the significance of El Niño conditions for Australia’s primary producers and communities, as well as for ecosystem recovery and disaster preparedness for this coming bushfire season in southeast Australia.
What do we know about the strength of this year’s El Niño event?
Dr Nandini Ramesh, Senior Research Scientist, explains:
“It’s still difficult at this point to say with confidence whether this will be a high-magnitude event. International forecasts suggest a moderate-strength El Niño event is the most likely outcome, followed by a high-strength El Niño event. The uncertainty about this comes from the atmosphere, which has had a relatively muted response thus far to the now well-established warm sea surface temperatures. How strong the El Niño event gets now depends on how the atmosphere evolves over the next few months.
“Note that the “strength” or “magnitude” of an event is measured (and forecasted) in terms of the sea surface temperatures in the eastern-central equatorial Pacific, and not in terms of its impact. In Australia, the relationship between event magnitude and impact is not linear: some of the worst bushfire years have been during relatively weak El Niño events (2019-2020, for example).
“The Bureau of Meteorology’s forecasts indicate that the Indian Ocean Dipole will likely be positive by August, which usually promotes drier conditions over eastern and southern Australia.”
What might this mean for the sea surface temperatures around the Equatorial Pacific, which broke the highest ever temperature on record earlier this year?
Dr Chris Chapman, Ocean Dynamics Team Leader, explains:
“We won’t know exactly where and how the strongest sea surface temperatures (SSTs) will pop up until an El Niño event gets underway. However, given the currently high SSTs in the equatorial Pacific, an additional “nudge” from El Niño could see record high SSTs in some regions.
“The response of equatorial Pacific sea surface temperatures to El Niño depends on where you are and the “flavour” of El Niño. Currently, sea surface temperatures between New Guinea and the dateline are typically either below average or near normal, while between the dateline and South America sea surface temperatures are generally higher (in some cases much higher) in an “Eastern Pacific flavoured” El Niño.
“In a “central pacific” flavoured El Niño, SSTs are higher than average around the dateline and lower than average off the coasts of both New Guinea and South America.
Is climate change making El Niño events worse?
Dr Jaci Brown, Climate Intelligence Director, explains:
“Our atmosphere is warmer due to climate change and so hot, dry conditions that are associated with El Niño are exacerbated. Whether El Niños are changed or made worse by climate change is a more complex question.”
Will an El Niño event make it more likely that the world will overshoot our goal under the Paris Agreement to limit warming to 1.5 degrees?
Dr Jaci Brown, Climate Intelligence Director, explains:
“El Niño years are generally warmer than other years over Australia and the whole globe on average. Australia is already 1.47 °C warmer as a long-term trend. We will see individual years go higher and lower than this. Globally the warming increase is around 1.1 °C and it is less clear how much higher this El Niño would warm the whole Earth – but it would only be for the period of the El Niño which would ease off in Autumn of 2024.”
Dr Nandini Ramesh, Senior Research Scientist, adds:
“Yes, it will make this more likely, at least temporarily. El Niño events involve the release of a large amount of heat from the ocean’s surface to the atmosphere, and the global average temperature record usually shows a short-term “bump” in temperatures during El Niño years as a result. Whether we cross 1.5 degrees in a more permanent way remains to be seen.”
Could we get three El Niños in a row?
Dr Jaci Brown, Climate Intelligence Director, explains:
“A more pressing question is whether we are about to head into a multi-year drought which is associated with many factors, not just El Niño. At this stage, our climate models cannot give us reliable forecast information beyond about 6 months. But we have seen multi-year droughts before and we will see them again.”
Dr Nandini Ramesh, Senior Research Scientist, adds:
“This is something we have not seen before; the longest El Niños have been about two years long. La Niña and El Niño are not perfect mirror images of each other, and La Niña events often last longer than El Niño events do.”
Are parts of Australia more susceptible to drought during El Niño events?
Dr Graham Bonnett, Lead, Drought Resilience Mission, explains:
“El Niño events don’t always lead to lower rainfall or droughts. Droughts occur after an extended period, such as more than a year, of much lower-than-average rainfall.
“We notice drought impacts more when relatively low rainfall years translate to poor crop and pasture growth, or prolonged dry years see water storage dams run low or empty. The timing of lower rainfall translating to poorer crop and pasture growth will depend on the amount of starting soil moisture.
“While drought can technically happen anywhere, it’s often the regional communities that rely heavily on agriculture who are most affected.
Australia’s south is expected to experience less rain in future in general. This long-term drying trend may increase the region’s susceptibility to impacts of lower rainfall years in future.”
What can Australia’s primary producers do to prepare for possible drier conditions?
Dr Graham Bonnett, Lead, Drought Resilience Mission, explains:
“Livestock producers can monitor pasture growth and make stocking adjustments to match feed availability as the year unfolds.
“It’s also important to monitor the amount of soil moisture relative to crop development. If it turns out to be a low rainfall year, crops can be conserved as hay or silage rather than going through to grain.”
Will ecosystems like those in the Murray-Darling Basin have a chance to recover from flooding events earlier this year?
Dr Francis Chiew, hydrologist and Group Leader explains:
“It’s too early to predict how a potential El Niño event may impact flows in the Murray-Darling Basin. The good news is wet conditions from three successive years in La Niña years have filled our reservoirs and provided what is essentially a buffer for the system.
In terms of the bigger picture, we can certainly expect droughts to become more frequent and more severe in the decades ahead, which will paint a more complex picture for recovery.
We’ve always managed our water ecosystems around the swings of flood risk and planning for droughts. However, climate change means that we also have to manage a drying trend – meaning that droughts are expected to become more frequent and severe.”
Should we be worried about an increased fuel load in the lead-up to southeast Australia’s bushfire season and an El Niño event?
Dr Andrew Sullivan, Leader, of Bushfire Behaviour and Risks, explains:
“An El Niño event does not necessarily mean that a bushfire season will be a big one. However, the last few years have seen exceptional growing conditions for vegetation in most agricultural and bushland areas, particularly in south-eastern Australia. At the same time, wetter conditions have also made it more difficult for authorities to implement their planned hazard reduction burns in many locations. Bushfires still require elevated fire weather and ignition sources for increased vegetation growth to shift to a potential for increased available fuel and the potential for widespread bushfires.
“If we face consecutive El Niño events and extended periods of decreased rainfall, then increased vegetation growth from recent years could become available bushfire fuel. Areas of open vegetation, such as agricultural lands, grasslands and woodlands follow an annual burning cycle. The threat of bushfires will transition from these areas to forests, where multiple years of drying vegetation heighten the potential for increased fuel and potential for large intense fires if ignitions coincide with extreme fire weather events.”
Chief Research Scientist, Dr Pep Canadell adds:
“Depending on where drought hits the most during this coming El Niño, we could have a big fire season in the grass-dominated rangelands in large parts of the continent and savannahs of the north, where the build-up of grass biomass over the past three wet years can quickly dry and become flammable to fire.”
“In the eastern and southern parts of the country, open woodlands could be equally exposed to high fire risk, but we expect forests to continue to be wetter than average from La Niña years, making it less likely that fuels will be primed for a big forest fire season.”
Can we expect more dangerous bushfire weather as a result of climate change and El Niño?
Chief Research Scientist Dr Pep Canadell explains:
“Weather conditions conducive to bushfires in Australia have already increased over the past two decades, particularly in the southern and eastern parts of the country. This trend is consistent with the observed increase in forest burned areas and megafire seasons. Projections for the next decades under all future climate scenarios show that fire weather will continue to increase. The length of the bushfire season increases when weather conditions are conducive, and fuels and an ignition source are available.”
Can bushfires during El Niño years exacerbate greenhouse gas emissions?
Chief Research Scientist Pep Canadell Dr Pep Canadell explains:
“Yes. While the Australian landscape tends to be a large carbon sink during La Nina years, it reverses to become a carbon source during El Niño years. This is because the amount of CO2 sequestered by vegetation is closely related to the amount of water that is available. A strong El Niño event could therefore limit the ability of vegetation to sequester carbon dioxide from the atmosphere.
“An increase in drought conditions can lead to fires, which would further exacerbate emissions.”
What has changed in terms of forecast and safety technology since the 2019/20 bushfires?
Principal Research Scientist, Dr Fabienne Reisen explains:
“We have extended the smoke forecasting capability Air Quality Forecasting System (AQFx) to be available to all states and territories in Australia. The AQFx forecasts and relevant smoke observation data are displayed in a cloud-based visualisation application called the Air Quality Visualisation system (AQVx). It provides a tool for managing population exposure to smoke.
“We have also assessed the performance of AQFx for the 2019/20 bushfires. This has driven the development of improvements to increase the accuracy of the AQFx forecasts. We have also started deploying low-cost particle sensors called SMOG units to WA, SA, and NT to cover sparsely monitored areas.”
Principal Research Scientist, Dr Andrew Sullivan adds:
“Rural fire authorities and land management agencies across the country have continued to improve their ability to plan for and respond to wildfires. A new Australian Fire Danger Rating System, largely built on CSIRO’s bushfire behaviour science, was introduced prior to the 2022/23 fire season. It continues to be refined to help communities understand their daily bushfire danger.”
“A new next-generation wildfire spread simulation tool called Spark Operational was also rolled out nationwide recently. This tool, developed by CSIRO in conjunction with the Australian National Council for Fire and Emergency Services, will help rural fire authorities predict the likely behaviour and spread of bushfires across the landscape so they can better plan and implement suppression actions as well as issue timely warnings to communities.”
