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Indian Ocean linked to bushfires and drought in Australia

In a study released today in Nature Geoscience, we show that extreme weather events in Australia such as drought and bushfire are linked to temperature changes in the Indian Ocean. Much like El Niño in…

Cooling oceans off the coast of Indonesia can create bushfire weather in Australia. AAP Image/Dan Himbrechts

In a study released today in Nature Geoscience, we show that extreme weather events in Australia such as drought and bushfire are linked to temperature changes in the Indian Ocean. Much like El Niño in the Pacific Ocean, the Indian Ocean Dipole has far-reaching consequences, and these effects are likely to strengthen under climate change.

What is the Indian Ocean Dipole?

Like El Niño, the Indian Ocean Dipole (IOD) is an interaction between the ocean and atmosphere.

The IOD appears and develops in the Southern Hemisphere winter and matures in spring. In its positive phase, which is the one that interests us most, sea temperatures off the cost of Sumatra and Java are lower than normal. Meanwhile in the western equatorial Indian Ocean, off the coast of Kenya, sea temperatures are warmer.

(The IOD also has a negative phase, but this is much rarer, and its effects much more benign.)

These seemingly small changes in sea temperature have profound effects on the atmosphere. Convection — rising warm, moist air — and rainfall tend to follow the warmest sea temperatures. So changes in sea temperature dramatically alter atmospheric circulation and rainfall distribution.

The result, in the case of the IOD, is extreme weather in many parts of the world, including severe droughts in Indonesia and devastating floods in East African countries.

For Australia, our research confirmed links between this Indian Ocean phenomenon and extreme weather events in southeast Australia, for example, bushfires such as those that occurred on Black Saturday.

During a positive IOD event, south east Australia sees decreased rainfall and increased temperatures. This is because much of the moisture supplying rainfall over south east Australia in winter and spring come from the tropical eastern Indian Ocean. Less rain and clear skies lead to higher temperatures than normal.

Cool waters over the western Indian Ocean cause drought and extreme fire conditions in Australia. CSIRO

More than a statistical fluke

In earlier studies, scientists showed that there are statistical links between the IOD and extreme weather in Australia.

In this new research we’re able to show that these linkages are not statistical flukes, and can in fact be predicted by climate models.

And because these events can be simulated by models, we can use these models to find out whether positive IOD events will become more common in a warming world.

We examined 54 climate models and experiments that participated in the International Panel on Climate Change’s Fifth Assessment Report. These model experiments include the historical period up to 2005, and a future period under a high emissions scenario. These experiments provide a large number of samples with thousands of years of virtual climate, which allows us to distill climate change signals.

How might the IOD change in the future?

Over the past 50 years, the IOD index (how we measure the difference in sea temperatures between the western and eastern Indian Ocean) has been trending upwards. Climate models suggest it will continue to do so over the next 100 years.

This predicts a drying trend over south east Australia, and more IOD events compared to the present climate.

In a warming world, the eastern Indian Ocean warms less than the west, and tropical rainfall and moisture move away from the eastern Indian Ocean, resembling a positive IOD event.

This slow warming pattern will lead to more frequent IOD events, and the associated dry conditions will be more intense, compared with the present-day climate. The bottom line is that the rain is moving away from Australia.

What does this mean for Australia?

Our major bushfires in summer have been linked with a positive IOD in winter and spring, and therefore the IOD offers a way of predicting summer bushfire conditions. This research enables us to better anticipate drought and increased bushfire risk.

This is because we have some four to six months of lead time before the fire season. An IOD in winter and spring is a warning sign of higher than normal fire risks in the upcoming summer.

In future climate, a decline in spring rainfall and a rise in temperature induced by an IOD event, exacerbated by a long-term drying trend in a warming climate, will greatly increase the risk of major bushfires.

The implications are of course far broader than Australia. The IOD has, to date, preconditioned wildfires in Indonesia, caused coral reef death across western Sumatra, and exacerbated malaria outbreaks in East Africa. We expect these extreme events to become more intense in the future.

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39 Comments sorted by

  1. David Arthur

    resistance gnome

    Thanks for this article, Dr Cai.

    Here, expected declines in rainfall over Southern Australia are attributed to increasing propensity for particular modes of Indian Ocean currents.

    Elsewhere, on the other hand, I've read of similar declines in rainfall over Southern Australia being attributed to poleward migration of mid-latitude climate belts which are in turn attributed to intensification of Hadley circulation and consequent expansion of sub-tropical high pressure belts.

    I've even read of the same predicted trend being in part caused by polar stratospheric cooling due to ozone loss (which may recover this century).

    Can you comment on any relationship between these suggested mechanisms?

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  2. Greg North

    Retired Engineer

    There are studies that do link ENSO with the IOD and monsoonal weather strength with scientific study having coined the Indian Ocean equivalent of the ENSO, the EQUINOO.
    It is a known fact and has been known for many years by anyone in Australia having a dip in the briny that water temperatures cool considerably in southern winter/spring and do take a fair bit of summer to warm up even a couple of degrees, it being less pronounced the further north into Queensland one goes.
    It is true that much…

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  3. Mark McGuire

    climate consensus rebel

    Quote:"Much like El Niño in the Pacific Ocean, the Indian Ocean Dipole has far-reaching consequences, and these effects are likely to strengthen under climate change."
    As there is a history of 'climate change' to check with when it was warmer, there is no example offered of these 'effects' being stronger because of 'climate change.' If the inference is 'higher levels of carbon dioxide' cause stronger climate change, again where is the historical evidence? And, if by chance anyone finds an example, why wasn't it 'catastrophic' then? http://rogerfromnewzealand.files.wordpress.com/2010/01/global-temp-co2-over-geological-time.jpg

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    1. David Arthur

      resistance gnome

      In reply to Mark McGuire

      Perhaps some of these might help?

      Santoso et al (includes Dr Cai) "Late-twentieth-century emergence of the El Niño propagation asymmetry and future projections",
      Nature (2013) doi:10.1038/nature12683

      ENSO variance reconstruction of McGregor et al's "Inferred changes in El Niño–Southern Oscillation variance over the past six centuries" Clim. Past, 9, 2269-2284, 2013
      www.clim-past.net/9/2269/2013/
      doi:10.5194/cp-9-2269-2013

      Oppo et al (2009), "2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool", Nature 460, 1113-1116 | doi:10.1038/nature08233

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    2. Greg North

      Retired Engineer

      In reply to David Arthur

      I would suggest David that not many weather researching people would relate ENSO variations to just the twentieth century.
      Go back a little more than a century to the 1890s and you'll discover how in that decade something like four or five mammoth magnitude Brisbane River floods occurred.
      Go back a thousand years if it was possible and there would no doubt have been ENSO variations and no doubt for every thousand tyears preceding.

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    3. Felix MacNeill

      Environmental Manager

      In reply to Greg North

      I wasn't aware that anyone WAS suggesting that ENSO was purely a twentieth century phenomonon. You need to make the distinction between a pattern of variations (ENSO) and a variation to that pattern (climate change impacts on ENSO).

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    4. David Arthur

      resistance gnome

      In reply to Greg North

      Thanks for that comment, Mr North.

      If it's of any help, the articles to which I refer Mr McGuire are concerned with (paleoclimatic) "reconstructions" of past temperature and ENSO records.

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    5. Sean Arundell

      Uncommon Common Sense

      In reply to Mark McGuire

      Many are good at asking leading questions that they believe are sound or might sew some doubt in the minds of the ignorant and not knowing. I suspect such comments and urls to blog sites won't dint the confidence the scientists have in the study quoted in the article. I don;t know what people like Marc are thinking but i do know this:
      It is possible that a major error has been made in climate science and the reason it hasn't been picked up yet is due to group think. Anything is possible. Far less…

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    6. Sean Arundell

      Uncommon Common Sense

      In reply to Mark McGuire

      Some Factual Orientations
      The IPCC has produced a video on its Fifth Assessment Report (AR5) http://climatestate.com/2013/11/28/climate-change-2013-working-group-i-the-physical-science-basis/

      The AR5 WGI Report is a 2200+ pages detailed compiled summary of the state of the physical scientific basis of Climate Science up to 2012. This report includes over 20,000 separate citations drawn from over 9.000 separate peer-reviewed published Scientific Papers (Studies, Research Projects, Modelling Analyses…

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    7. Sean Arundell

      Uncommon Common Sense

      In reply to Greg North

      Learn to read Greg .... eg over the past six centuries & 2,000-year-long BEFORE hitting the "post comment" button. Far less embarrassing imho. Unless it doesn't matter to you, which is fine by me. No worries. :)

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    1. Greg North

      Retired Engineer

      In reply to Jack Arnold

      Are you unfamiliar with southerly busters Jack?
      And if you have ever lived in northern NSW or Queensland, you would know that in addition to monsoonal overflows that cometh around approach to and in northern wet seasons ( which have always varied btw ), you would also be accustomed to chillier winter/spring temperatures that would accompany snow falls on our barely Alps.
      Yes, all that weather cometh from the southern ocean that brings us snow more than often has cold streams venturing right up to southern Queensland.

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    2. Jack Arnold

      Director

      In reply to Greg North

      Yes Greg, I am aware of southerly busters. You can see them forming SW of WA in the Southern Ocean before they flow over the Australian land mass. Check out the BOM website, it is quite spectacular.

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    3. Sean Arundell

      Uncommon Common Sense

      In reply to Greg North

      There was no snow ski season this year Greg. I know my sons were there and they and everyone else who had season jobs packed up early after 3 weeks or so. Waste of time.

      I have been going to Mt Warning National park since I was 6 years old. The canopy is opened up in multiple places, white ants have been into the trees for over a decade, and maybe 30% of the older 500+ year old trees have fallen over, and the soil is basically dry unless it rained yesterday. It is not the same forest it used to be. Not in a long shot.

      Please educate yourself about the difference between weather and climate. The climate has noticeably and statistically changed in Gladstone, Bundaberg, Sunshine Coast, Brisbane, Gold Coast, Beaudesert, Towoomba, Nth NSW areas like Casino, Nimbin, Byron Bay, Ballina, Grafton ... all the way down to Sydney and Woolongong and the southern tablelands and the Alps compared to the 1960s and 1970s period.

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    4. Greg North

      Retired Engineer

      In reply to Sean Arundell

      Sean, even if you may have been around a few years longer than me, I am sure like myself you are educated enough to know that yep Snow seasons can vary dramatically in Australia just as the climate can too from decade to decade and throughout the hundreds and thousands of centuries that planet earth has been developing.
      I've skiied in Victoria on Melbourne Cup weekend a couple of decades back, getting a bit slushy by then and for sure a bumper season and I doubt in our more northern climes that…

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    5. Sean Arundell

      Uncommon Common Sense

      In reply to Greg North

      Greg thanks for response. I believe that I totally get your point of view and understand why you hold to it.
      I agree with you that: "yep Snow seasons can vary dramatically in Australia" and "climate can too ... throughout the hundreds and thousands of centuries" and " more northern climes that the termites will be too fussed with what the weather at Mt Warning" and "A decade or so back I know the Gold Coast was so dry at times" [and had been before too at times], and [i have] " heard of people…

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    6. Sean Arundell

      Uncommon Common Sense

      In reply to Sean Arundell

      About the References:

      Greg and others have you yourself read the AR5 WGI Summary for Policy Makers? It is only 36 pages long - see 2013-09-27 WGIAR5-SPM_Approved 27Sep2013 [Summary]

      If not, why not?

      Have you also read those references listed in the SPM provided by the IPCC WGI? If not, why not?

      Greg and others have you read or already know what the AR5 WGI Full Report - Final Draft Underlying Scientific-Technical Assessment? It is 2,216 pages long? If not, why not? It has been publicly…

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    7. Sean Arundell

      Uncommon Common Sense

      In reply to Greg North

      And Greg, this is why 'detailed records' matter. "The spring of 2013 has been Australia’s warmest on record. Mean temperatures for the season were 1.57C above the 1961-1990 average"

      It separates subjective guesses and opinions from more valid well reasoned anecdotes that can be supported by OBJECTIVE the data (eventually).

      https://theconversation.com/australia-records-its-warmest-spring-20821

      The day the arctic starts reforming to the sate it was in in 1908, when high temp records stop being broken at the rate to 20 to 1 of cold records, when storms wind speeds stay lower over a decade than the decade before, then I will start paying attention to the opposite pov of view. Until then, I really like using the science to explain what my own eyes keep seeing, and most other peoples eyes as well.

      What to do about it? That's another question that is far less clear and has far less agreement than AGW/CC science possesses. Cheers Sean.

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    8. Sean Arundell

      Uncommon Common Sense

      In reply to Greg North

      Greg, another PS re: "It has been confirmed that even the IPCC 2C is a politically creative benchmark and that being so, just how much is known of human activity inducements Vs nature's cycles is still even more questionable."

      See was this really the doing of the IPCC or scientists? No it wasn't. It came into being by agreement of all (well almost) National Governments at the UNFCCC meeting in 2009.

      INTERNATIONAL Copenhagen Accord
      ‘ To hold the increase in global temperature below 2
      degrees…

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    9. Doug Hutcheson

      Poet

      In reply to Sean Arundell

      Sean: "4C is more likely by 2050 or soon after". Really? I thought these projections were for the end of the century, not the middle. 4°C by 2050 sounds a bit implausible to me, but I agree that 4° is more likely now than 2° by the end of the century.

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    10. Sean Arundell

      Uncommon Common Sense

      In reply to Doug Hutcheson

      Yes yes, the formal IPCC projections, when mitigation is applied comes out at that level not until 2100. True.

      Sorry I was tossing in my own personal opinion there, I should have made that clear.

      I say this 4C by 2050 or shortly thereafter on the grounds of a good assumption of no genuine mitigation occurring pre-2030, that 2C is already at threshold and measured temps will shortly reflect that imho, as in most heat being absorbed by the oceans for decades now tending to become blow back…

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    11. Sean Arundell

      Uncommon Common Sense

      In reply to Sean Arundell

      37°C and above - Killing their workers

      She said the Australian Government was ignoring climate change and still expecting places like Darwin (* see note) to expand. But that was unlikely because they would soon become untenable. “If employers ask people to continue to work in temperatures above 37°C, they will be killing them in increasing numbers,” she said.

      Dr Hanna said humans were well suited to living in cool conditions and felt comfortable in temperatures between 20°C and 23°C because…

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    12. Doug Hutcheson

      Poet

      In reply to Sean Arundell

      Sean, "I was tossing in my own personal opinion there". I have to say I agree with most of your analysis and my worst nightmare is that we do, indeed, hit 4°C by 2050. Like you, I think we will go right on past 4° without blinking. Homo Stupidus stupidus.

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    13. Sean Arundell

      Uncommon Common Sense

      In reply to Sean Arundell

      More on a 4C world

      ELEANOR HALL: While the Federal Government focuses its climate policy energies on repealing the carbon tax, a report published today paints a terrifying picture of a world that's four degrees warmer and recommends a dramatic increase in Australia's carbon reduction target.

      PETER CHRISTOFF: Well, two years ago or four years ago, it would have been regarded as science fiction to think about a world heading in that direction. But frankly, given the pace of negotiations and the…

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  4. Kyran Graham

    PhD Candidate: Neuropsychiatry/Neuropsychology at University of Western Australia

    Thanks for the excellent article!

    I have one question (that possibly requires a whole article!): Given that the ENSO affects global weather patterns, I'd assume that there would be some form of interaction between the two variations, so how do the Indian Ocean Dipole and El Niño/La Niña interact and how does that affect weather in Australia?

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    1. Wenju Cai

      Principal Research Scientist, Wealth from Oceans Flagship at CSIRO

      In reply to Kyran Graham

      Hi, thank you for your comments.

      The two do interact, and each can be triggered by the other. An positive IOD (cooler in the east, and warmer in the west) often occurs concurrently with an El Nino.

      But each can also occur independently. For example, 2007 and 2008 were actually La Nina years. But we had a positive IOD in each of those two years. As such our drought continued. The IOD has over powered the effect of La Nina, which tends to give us more rain.

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  5. Colin Creighton

    Chair, Climate adaptation, Marine Biodiversity and Fisheries

    Thanks Cai for the article.

    The more we all recognise that climate is a massive interlinked system of multiple forces, interactions and feedbacks and impacts the better.

    Silver bullets are out - systems understanding is the pre-eminent challenge.

    The more resources to dynamical modelling preferably as an international multi-nation multi-disciplinary endeavour the better. Lets hope in time we can deliver global climate services and early warning predictive forecasting to all nations. Knowledge and preparedness saves lives.

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  6. Ai Rui Sheng

    Retired

    Thank you Cai Ai for inviting Alan Jones, the PM and News Ltd to the real word. However I fear they will continue to cling to their 4,000 year old virtual world.

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  7. Doug Hutcheson

    Poet

    "the Indian Ocean Dipole has far-reaching consequences, and these effects are likely to strengthen under climate change." Not a happy projection. If I understand correctly, the dipole is the difference in temperature between east and west: what happens if BOTH become warmer, in synch? The same temperature east and west would eliminate the dipole, would it not?

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  8. Sean Arundell

    Uncommon Common Sense

    Dear Wenju Cai, Researcher at CSIRO congratulations to you and all your team on the publication of your study and the long hard hours of work behind it. Thank you also for your excellent article here. I hope you are able to contribute many more like this into the future for the benefit of everyone. Best, Sean

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    1. Wenju Cai

      Principal Research Scientist, Wealth from Oceans Flagship at CSIRO

      In reply to Sean Arundell

      Thank you Sean, for your encouragement. Inspired. Regards, Cai

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    2. Jack Arnold

      Director

      In reply to Wenju Cai

      Cai, what about the research done by Australian Inigo Jones at the end of the 19th century? He predicted weather patterns based on the frequency & occurrence of solar flares, and my long weather watching neighbour believes that Jones has been more accurate than any of the BOM prognostications over the last 40 years.

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    3. Sean Arundell

      Uncommon Common Sense

      In reply to Jack Arnold

      I know about this issue, and would love to see a modern climate scientist analysis of all the data held now by Lennox Walker's son who is still operating long range forecasting. Also I think you'll find that was sunspots, not flares so much. (?) Also not only the sun is evaluated. My gut feel is that flagging weather is different to climate though. still i have no idea, but Hayden Walker is one who has dismissed climate science and co2 as well, unless he recently changed his mind. http://www.worldweather.com.au/History.htm

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    4. Jack Arnold

      Director

      In reply to Sean Arundell

      Thanks for the interesting link Sean. Perhaps our trolls will read and learn.

      So, if the SOI and IOD are linked, does this mean that a similar statistic can be developed for the DSouthern Ocean, probably SW of WA, to show the impact weather events in the Southern Ocean?

      We live in exciting times.

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    5. Sean Arundell

      Uncommon Common Sense

      In reply to Jack Arnold

      re "Also not only the sun is evaluated" I have friends who have lived up very close to where Inigo set up the work and Hayden is still there. I have known about them since the 60s, and was intrigued. Several years ago I did as much online research as I could and found a few things. The Walkers have been very careful not to let any of their knowledge leak out, so one needs to read what was available with reading between the lines and I also blended that with what I had been told by locals who knew…

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