Extract from ABC News
The likely onset of the El Niño climate driver has made headlines this year, raising concerns about a dry and hot spring and summer ahead for Australia.
El Niño is a major global event impacting on weather patterns around the world with a reputation as a nursery for bushfires and drought in Australia.
A look back at the 27 recorded El Niño events since 1902 shows the impacts have overwhelmingly had a dry influence on eastern Australia.
But the strength of impacts is a vast spectrum from widespread drought to, in some cases, no impact at all.
So how has El Niño behaved in Australia in the past, and can they offer clues for what may be in store this year?
1982-1983: The year of Ash Wednesday
The 1982-1983 El Niño was one of the most disastrous events recorded in Australia.
Drought conditions became widespread across eastern and southern Australia in April of 1982 and continued "almost unabated" up to February 1983, according to the Bureau of Meteorology.
These conditions culminated in the Ash Wednesday disaster when more than 100 fires swept across the parched landscape in Victoria and South Australia, killing 75 people and causing widespread destruction.
Monash University climate scientist Ailie Gallant said the event was often referred to as the "classic" El Niño, with "big signatures in the Pacific Ocean, big signatures in the atmosphere, and big impacts in Australia".
Its impact strengthened the scientific knowledge about El Niño and effect on Australia.
There are some aspects of the current El Niño which are similar to the 1982 event, namely projected sea surface temperatures in the eastern Pacific.
But Dr Gallant said people should not be looking at that analogue to draw conclusions about the potential impacts of this year's event.
Other El Niño events have shown the strength of the event does not directly correlate to its impacts in Australia.
1997-1998: A strong El Niño without strong impacts
Globally, the 1997-1998 El Niño was regarded as one of the most powerful El Niño events in recorded history, resulting in widespread droughts, floods, and other natural disasters across the world.
But the event had far weaker impacts for Australia, according to the bureau, although it was still dry for south-eastern states on the whole.
This event did shed light on the potential influence local ocean temperatures could have on Australia.
During this event, sea surface temperatures around Australia were only slightly cooler than normal, according to a study led by Peter van Rensch, which meant there was more moisture available in the atmosphere near Australia for weather systems to tap into.
Dr Gallant said similar observations of ocean temperatures near Australia were being made this year.
But, like the event of 1982, it did not guarantee the same outcome.
"Again, it depends what the Indian Ocean is doing [on the other side of Australia] and it kind of depends on a whole bunch of other factors," she said.
"Unfortunately we don't have a complete crystal ball."
2009-2010: The wet El Niño
While El Niño has overwhelmingly had a dry influence on Australia, the event of 2009-2010 showed it was not a guarantee.
Data from the bureau shows the initial phase did have a negative impact, with May to October "rather dry" over much of the country, especially in Queensland and the Northern Territory.
But by November the tables turned, ushering in a substantial "wet period" over the eastern half of the country.
For the five months from November 2009 to March 2010 NT, SA, Queensland, NSW, and Victoria all had areas of rainfall in the top 10 per cent of records.
This included the 2010 Melbourne hailstorm, which dumped ice stones up to 10 centimetres in diameter across the city and very heavy rainfall which caused extensive property damage.
2002-2003 and 2006-2007: The Millennium Drought
Other examples of high-impact El Niño events in Australia can be found in the early 2000s.
What set these events apart from 1982 was their strength.
Both events were considered to be fairly "weak" in terms of ocean and atmospheric conditions.
In Australia, however, their influence was strong.
Between 1997 and 2009 pockets of eastern Australia were facing repeated bouts of dry conditions — a period which later became known as the Millennium Drought.
During the decade there were two years in particular, in 2002 and 2006, which saw widespread dry conditions — the two El Niño years.
Julie Millowick, who travelled the south-east of Australia taking photographs of the landscape during this period, described the challenges faced by people on the land as "horrific", with bare paddocks and empty dams.
"People just had to cope with it, and cope with these challenges in any way they could," she said.
According to the Bureau of Meteorology "practically all parts of the country were affected, and in southern areas this exacerbated the effects of several preceding years of dry conditions".
2015-2016 : A double whammy of dry climate drivers
This very powerful El Niño left its mark on the entire world, making 2015 the world's hottest calendar year on record, only to be toppled again in 2016.
The world's oceans also recorded their highest ever daily temperature for the time.
In many ways, this year's event appears to be following a similar trajectory with records set in 2016 broken this year, and the ocean temperatures also looking similar in the Pacific, according to Dr Gallant.
But she said you could also argue this years event also had similarities to 2014 — the strong El Niño which never eventuated.
Despite its strong global impacts, in Australia the 2015-2016 event was only moderate, tempered by warm temperatures in the Indian Ocean when the event first kicked off.
It did however, contribute to a markedly drier than average northern wet season and the worst coral bleaching event on record for the Great Barrier Reef.
Future El Niño events' unknown qualities
Dr Gallant said the analogue of past El Niño events and their impact in Australia made clear that no two events were the same.
"You could look at any event and draw parallels at different times," she said.
"It's like that saying for superannuation funds — 'past performance isn't an indicator of future performance.'"
She said on top of that, climate change was "muddying the waters" and the way it affected El Niño and La Niña's behaviour in Australia was not fully understood yet.
Dr Gallant said this was particularly tricky when it came to rainfall.
"Trying to disentangle what climate change is doing as opposed to what it should naturally do, and understanding what those impacts should have on Australia, is very difficult," she said.
"The exact implications on rainfall — we don't know.
"But we do know that El Niño is hotter, so that then brings with it all sorts of other implications for things like fire and whatnot."
Nevertheless, she said Australians should be preparing for the strong likelihood of a dry and warm spring and summer ahead.
In its latest climate driver update, the Bureau kept its El Niño status at "alert" level, at odds with the rest of the world, saying conditions in the atmosphere were still not showing signs of a consistent El Niño state.
But it said the climate driver was still considered likely to develop in spring.
No comments:
Post a Comment