By Angus Blackman
The declaration of an El Niño by the Bureau of Meteorology has many Australians concerned about the prospect of extreme weather this summer.
This bushfire season has gotten off to a worrying start, with devastating blazes already destroying homes and killing several people during spring. Looming large is the spectre of the Black Summer fires of 2019-20, which directly killed 34 people and destroyed around 3,000 buildings.
Global conditions are also raising anxieties. Europe experienced record temperatures in the northern summer and 2023 may become the hottest year on record globally.
So, what is in store for Australia this summer? Honorary Lecturer and retired meteorologist Clem Davis shared his insights on the weather in Australia and around the world.
Will there be a heat wave?
Heat waves are lengthy periods — usually three or more days — of extremely hot weather at a specific location. They are responsible for more human deaths than other extreme events and affect the elderly and the young in particular.
Keeping hydrated, cool and out of the sun is very important during a heat wave, Davis says.
“This summer, Europe experienced an extreme heat wave event, caused by slow-moving or stationary high-pressure systems over southern Europe,” he says.
“This directed hot air from northern Africa to Europe for a lengthy period, causing extreme temperatures.
“Dry conditions, low soil moisture and clear skies were all contributing factors to the record temperatures, as was a slowing of the upper atmospheric jet stream.”
But while Europe’s summer was sweltering, that’s no real indication that similar conditions will occur in Australia in the coming months, according to Davis.
“Our summers tend to be driven by more local factors,” he says.
These include the El Niño-Southern Oscillation (ENSO) in the Pacific Ocean and the Indian Ocean Dipole (IOD). For the last three summers, Australia has seen La Niña conditions in the Pacific and a negative IOD, which has resulted in cooler and wetter summers.
“This summer, with the return of El Niño and a positive IOD, we’re likely to see drier and warmer conditions with a greater chance of heat waves.”
How does an El Niño phase contribute to hot weather?
The ENSO is a climate pattern that involves changes in water temperatures and atmospheric pressures across the Pacific Ocean. It has three phases: El Niño, La Niña and neutral.
“Normally in summer, northern Australia is under a low-pressure system and monsoonal conditions. In La Niña years, these low-pressure systems are stronger, dragging in more moisture and rain,” Davis says.
“However, in El Niño years, the low-pressure region tends to shift into the central Pacific Ocean and leaves northern and eastern Australia under relatively high pressure with less moisture and rain.
“With less cloud and rain, especially over eastern Australia, we are more likely to get higher temperatures.”
What does this mean for the bushfire risk?
Exactly what will happen is impossible to predict, as the risk will depend on how the summer progresses, but hot and dry conditions can increase the risk of fires breaking out and their severity, Davis says.
“The fires of the 2019-20 summer followed a couple of relatively dry years.”
“While the last three summers have been cooler and wetter than normal, it has allowed a build-up of grass and ground cover that could cause an increase in bushfire hazards this summer.”
The Black Summer bushfires left a lasting mark on Australia’s landscape. Photo: ANU
Regardless of how this bushfire season unfolds, Davis encourages people to be prepared and especially take note of the advice from the local fire and emergency services organisations.
“For instance, have an emergency kit ready for any rapid evacuation if required. Things to consider are food, water, clothes, medications, communication items, torches, prized family possessions and pets,” Davis says.
“Of particular importance is knowing how to escape and where will you go and if you are going to evacuate, do it early and don’t leave it to the last minute.”
How will rising global temperatures affect our summers?
The latest report of the Intergovernmental Panel on Climate Change (IPCC) found that global temperatures are likely to reach 1.5 degrees Celsius above pre-industrial levels in the early 2030s.
In the words of two of its authors: “The world is up the proverbial creek — but we still have a paddle.”
Davis says that while generally warmer conditions will lead to an increase in extreme events, it’s not totally clear how global warming might impact climactic patterns such as the ENSO and IOD, or exactly how people can cope with increasingly severe temperature extremes.
“El Niño summers tend to be warmer than normal, but it is very rare to get two consecutive El Niño events.
“However, the impact of climate change on ENSO events is still uncertain and under ongoing research.”
“Humans have adapted to living in both extreme hot and cold conditions. The dangers lie where extreme conditions develop that are well outside the normal climatic conditions for a specific location, and where humans (and animals and plants) are unprepared to cope with such extreme events.”
This article was first published by ANU Reporter.