Drought in Australia has traditionally been linked to El Niño events in the Pacific Ocean. Now new research shows that Indian Ocean variability rather than El Niño, is the key driver of the major droughts in south eastern Australia over the past 120 years. This surprise finding brings a fundamental new insight into the causes of Australia’s worst and most damaging droughts.
BRIEFING DETAILS:
DATE: Wed 4 February 2009
START TIME: 10.30am AEDT
DURATION: 29 min
VENUE: Online
The research shows that virtually all of Australia’s iconic droughts, including the Federation Drought (1895-1902), the World War II drought (1937-1945), and the present “Big Dry” (post-1995), are associated with fluctuations in ocean temperature known as the Indian Ocean Dipole.
The authors of this new research presented their findings at the online briefing. A rapid roundup of comments from other experts is also available below.
A press release from the University of New South Wales is available from Bob Beale (0411 705 435 bbeale@unsw.edu.au) if you’d like to arrange an interview with the authors.
SPEAKERS:
Professor Matthew England, Joint Director of the Climate Change Research Centre, University of NSW.
Dr Caroline Ummenhofer, Post Doctoral Fellow at the Climate Change Research Centre, University of NSW
PRESENTATIONS:
Full Briefing (WebEx):
View here
Matthew England’s Presentation:
Listen (mp3)
Caroline Ummenhofer’s Presentation:
View PowerPoint (pdf) | Listen (mp3)
Q & A Session:
Listen here (mp3)
Below several experts respond to this research.
Professor Gary Meyers is Director of the Integrated Marine Observing System (IMOS) at the University of Tasmania and is a co-author on the paper.
“This is an important paper because it focuses on multiyear droughts in south eastern Australia. Most studies have been concerned with seasonal conditions, the one year droughts that develop with El Nino; they are associated with sea surface temperature in the Pacific Ocean.
The multiyear droughts are associated with the Indian Ocean according to this paper. The key factor seems to be the disappearance of conditions that favour high rainfall, unusually warm water in the region between Australia and Indonesia. For a reason not yet known, the periodic warming did not occur in this region during the three great multi-year droughts since 1900. The long persistence of this condition suggests that ocean circulation is involved, because ocean currents change slowly relative to the atmosphere, but the authors have not yet identified why the condition persists for such a long time.”
Professor Greg Skilbeck is Professor of Earth Sciences and Associate Dean (Research & Development) in the Faculty of Science at the University of Technology, Sydney. He has worked extensively on the past history of the ENSO (El Nino and La Nina) cycle.
“The concept outlined in the paper is relatively straight forward – the Indian Ocean Dipole (IOD) is the Indian Ocean equivalent of the Southern Ocean Index (the atmospheric driver of El Nino and La Nina, also known as the ENSO cycle). It has been known for a while that the correlation between ENSO cycles and rainfall/drought in Australia is not good (although it does improve when in phase with another phenomenon known as the Pacific Decadal Oscillation).
What the researchers have done is to find a more robust link between the Indian Ocean and rainfall in south eastern Australia over a relatively short time period (120 years or so). Clearly, rainfall in Australia is influenced by all surrounding oceans – the source of the water – so it is not surprising that the Indian Ocean plays a role.
The predictability associated with any of these phenomena, however, remains elusive (as is recognised by the authors). The “6 month” or so predictability is not really predictability at all – this is just the time lag between measurement of the indices in the relevant ocean and the time they take to manifest in Australia – and it is not really on the time scale needed for real planning. So are we any closer to understanding and therefore really predicting when extended droughts occur? Maybe, but how much closer is not clear.”
For further information, please contact the AusSMC on 08 8207 7415 or email us.