EXPERT REACTION: BOM declares an El Niño

El Nino, in Australia, is related with drier and hotter conditions, leading to prolonged droughts, reduced rainfall, and increased temperatures. These hot and dry conditions can lead to protracted bushfire seasons; fires starting much earlier and burning for longer. This is already becoming evident – with bushfires starting to burn in parts of NSW, Queensland and NT, much before the “official” bushfire season.

With El Nino creating conditions that make bushfires more prevalent – Australia’s responses to the fires must change. Policymakers will need to identify strategies that will future-proof communities against bushfires.

Australia should consider the establishment of a ‘fire-line’ – a bushfire demarcation line to identify high-risk areas not recommended for human habitation. In the same vein as Goyder’s Line of rainfall (created in South Australia 1865 to map areas liable to drought and therefore unsuitable for planting crops), a fire-line would help people clearly recognise areas that are suitable, or not, for living.

As people build their homes, and as governments invest in building schools, communities and the wider infrastructure, they need to be asking the question – is it actually safe to do so in these areas? A fire-line will assist people and policymakers in dealing with this moral and economic dilemma.

With climate change and El Nino, fierce blazes will keep burning. As bushfires continue to rage into residential areas, governments must consider more ground-breaking initiatives. A fire demarcation line (using CFS aerial footage, satellite imagery, and well-developed insurance company models) could help achieve this.

With the declaration of El Niño and a positive Indian Ocean Dipole, people should expect a hot and dry spring and summer.

I encourage people to use the next couple of weekends to cut back excess vegetation around their properties if they live in a fire prone region and pester their landlord to install an aircon because fire and heatwaves are likely hazards over the next six months.

After three consecutive years of La Niña, the Bureau of Meteorology has declared that the climate system has now shifted into El Niño. A positive Indian Ocean Dipole event, the El Niño of the Indian Ocean, has also been declared.

El Niño typically reduces the chance of spring rain in eastern Australia and increases the chance of warm days. A positive Indian Ocean Dipole tends to reduce the chance of spring rain in central and southeastern Australia. The Bureau of Meteorology’s outlook indicates warmer and drier conditions for most of Australia in the upcoming three months.

When El Niño and the positive Indian Ocean Dipole co-occur, drying in Australia is typically amplified. The last time El Niño and the positive Indian Ocean Dipole occurred together was in 2015.

With the onset of El Niño weather conditions we are likely to see extended periods of dry weather and high temperatures. We must look at innovative ways to protect existing ecosystems and species and to bring about resilient, restored ecosystems.
 
The possible impacts on plants including widespread plant death and decline due to drought conditions will have a serious impact on the resilience of plants and vegetation, poor seed set and in some situations dieback and decline.

El Niño conditions hamper efforts for rainforests to restore and rehabilitate damaged ecosystems making it difficult to recover the functionality of these ecosystems.

The period since the Black Summer fires to now hasn’t allowed all species to recover, grow and age enough to replenish seed stocks, recover from fire damage and germinate to grow to a sufficient size to regenerate the seed banks in soil.

Conditions in the Pacific and Indian oceans have been brewing for a few months now, and this declaration now makes it official. Eastern Australia is already experiencing some of the impacts that an El Niño and positive Indian Ocean Dipole event can bring. These climate drivers — on top of background warming due to climate change — means we need to prepare for a hot and dry end to 2023.

An El Niño pattern has developed in the past few months in the tropical Pacific, but the atmosphere has been slower to respond to the ocean warming. The Bureau’s declaration today means that the atmosphere is finally responding to the El Niño warming. El Niño is generally associated with below-average rainfall and increased chances of droughts and heatwaves over east/southeast Australia.

The El Niño event that has been forecasted with high confidence since the winter is now officially here, with impacts already being felt around the world after three years of La Niña conditions. For Australia, this means drier and warmer than normal conditions over most of the continent over the next several months. However, three rainy La Niña years have provided us with a buffer against drought, with soil moisture and reservoir levels still high. While the risk of fire weather is higher and preparedness is crucial, this buffer means that we are not necessarily guaranteed a catastrophic fire season this year.
 
This year’s El Niño is developing during some of the warmest global average temperatures in history, meaning that scientists are still learning how El Niño and its impacts are changing as this event unfolds in a warmer world.

While many of us are basking in the warmer weather, the long-range forecast for Australia suggests we are likely in for a warmer, drier summer – and that means we all have to be extra vigilant and work to make our properties and communities as bushfire safe as possible. 

The Bureau of Metrology El Nino alert continues and many key international weather agencies such as the US National Atmospheric Administration (NOAA) and the World Meteorological Organization have declared El Nino is underway. 

El Nino is a climate pattern that can significantly impact our weather. As individuals, we can’t impact this climate pattern in the short term, but we can take time now, before the busy summer season, and prepare our homes and properties. We can take time to make sure our Bushfire Survival Plans are up to date, and that everyone in the house is aware of the plan and knows what they can do if they are together or alone in the home if an incident occurs. 

It may sound over-zealous, but assigning a day and rehearsing your bushfire plan, could help you identify areas for improvement and importantly, that rehearsal could be invaluable if you were to experience a fire. Lastly, talk to your neighbours. It takes a community to make an area bushfire safer. Consider offering to help people with mowing, pruning or clearing gutters, or give them a link where they can find useful information. All our Country and Rural fire services have excellent resources on their websites to help with fire preparation.

With the Pacific Ocean strongly influencing our spring weather in Australia, El Niño is likely to bring warmer and drier conditions for much of the continent as well as an increased chance of more heat events and flash drought. The unusually hot weather we're seeing across southeast Australia at the moment is a warning of the kind of extremes we're likely to see more of over the next few months. Coming on the back of consecutive La Niña events, this spring will likely be very different and we need to be prepared for more heat, drought and fire weather conditions.

There is good evidence that El Nino increases the risk of hot, dry conditions that can increase fuel availability, ignition likelihood and dangerous fire behaviour, particularly in eastern Australia. The effects won’t be the same everywhere and El Nino is not the only climate driver that influences bushfire risk, there’s also the Indian Ocean Dipole and the Southern Annular Mode.

Crucially, any additional warming we see as a result of El Nino this summer will come on top of decades of human-caused climate change that has already significantly raised temperatures and bushfire risk in many areas. Without much stronger climate action than we are currently taking, we can expect to see much worse conditions in the future.

Leading up to the El Nino declaration we have heard a lot about the expected dry and heat of spring and summer, and extreme fire danger with comparisons to the 2019/2020 bushfire season in southern and eastern Australia. The two multi-year La Ninas 2010-2012 and 2020-2023 somewhat masked the statistically significant, insidious drying and warming that has been occurring from about the mid-1990s. For example, bushfire regimes have changed in southeast Australia since the late 1990s. 
 
Similarly, the Murray-Darling Basin (MDB) has been drying out since the 1990s because the catchment rainfall in all the dams, north and south, has decreased significantly in April-May and it continues to dry through winter even with just average or just below average rainfall.

By the time spring and summer arrives, soil moisture is very low, and vegetation is moisture deficient. Sufficient soil moisture needs to be present in spring leading into summer. And so the cycle goes on progressively getting worse without the occasional wet year or two (e.g. here and here). 

There are over 3 million users that rely on MDB rivers for drinking water, including 40 First Nations groups. It is home to 50 native fish species. 30,000 wetlands, including internationally significant ones, and farmers and irrigators rely on quality water for their continued existence. The devastating fact is that water demands will continue to exceed supply most of the time because long-term rainfall is significantly decreasing in the dam catchments when historically there used to be some runoff in the ‘Autumn Break” followed by some winter rain to continue wetting catchments and running off into dams.

Water buybacks are the only tool that governments can use but they won’t fix the problem because there is just not enough rain falling in the catchments and dams in most years. Remember in 2019, most dams in the northern MDB were below 50% storage and a lot below 10%.

Humidity has decreased significantly leading into winter in parts of southeast Australia since the 1990s owing to changes in the jet stream structure and atmospheric circulation (e.g. here). 

Decreased humidity increases evaporation and evapotranspiration, hastening the reduction in water supply.

The higher average temperatures and decreased predicted rainfall in eastern and southeastern Australia will likely have a negative impact on mosquito populations breeding in inland waters, such as wetland systems, groundpools, overflow, river channel backwaters etc. Such mosquito species likely to be affected and less abundant include Culex annulirostris, the main vector of Murray Valley and Japanese Encephalitis.

Coastal mosquitoes breeding in intertidal marshland are likely to be unaffected by El Nino, and may increase with higher temperatures. Mosquitoes breeding in urban environments (in containers, tanks etc) will also likely remain high in number.

In general terms, Australia suffers from less mosquito-borne disease in El Nino years, due to the reduced rainfall and subsequent reduction in mosquito breeding. Furthermore, some of the wildlife that harbours mosquito-borne viruses (e.g. waterbirds and kangaroos) will also be less abundant. These factors may contribute to a decreased amount of human cases of mosquito-borne diseases in Australia. However, the impacts are likely to vary regionally.