Sunburnt country set for long thirst

27 Apr, 2015 02:00 AM
Pretty much everywhere can expect to spend more time in drought

DROUGHT, that most undesirable element of Australian agriculture, is going to be more frequent and more severe in the decades ahead.

That’s the sombre warning of a Climate Council report that maps current trends into a future where drought frequency and severity is increased as the planet grows warmer.

The effects will be felt in agriculture, in particular, but also on urban water supplies, native ecosystems and the public purse as governments are called on to provide drought relief more frequently.

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  • The report, Thirsty Country: Climate Change and Drought in Australia, notes that warming has already produced substantial drying in south-west Western Australia, which has lost 15 per cent of the annual average rainfall it had in the 1970s, and in south-east Australia, where soil moisture deficits are increasingly common.

    Both patterns appear related to the same global warming phenomenon, the movement south of cool-season rain-bearing fronts out into the Southern Ocean.

    How these fronts track as they roll eastward off the Indian Ocean is largely determined by the subtropical ridge, a band of high pressure that tends to lie across Australia.

    The intensifying of the subtropical ridge as the planet has warmed has pushed the movement of the fronts south - by some estimates, already up to 300 kilometres - so that they more frequently move across the Southern Ocean and less frequently over land.

    The Bureau of Meterology and CSIRO estimate that 80pc of the rainfall decline in south-east Australia can be attributed to this shift.

    Temperatures climbing

    Meanwhile, things are growing hotter.

    Australia had its warmest year on record in 2013. Since 2001, the number of extreme heat records in Australia has outnumbered extreme cool records by almost 3 to 1 for daytime maximum temperatures, and almost 5 to 1 for night-time minimum temperatures.

    By increasing soil temperatures and evaporation rates, higher temperatures increase the severity of events like the Millenium Drought (1997-2010) of south-eastern Australia.

    Lack of rainfall and high temperatures reinforce each other to cause a cumulative rainfall deficit - deep drying of soils and landscapes that need several years of above-average rainfall before returning to baseline health.

    The report’s author, Will Steffen, said although rainfall trends are harder to forecast that temperature, it seems possible that annual averages may not change much, but the distribution of the rain events will, leading to more drought.

    “There is now pretty convincing evidence that across the southern part of the country it’s going to get drier, especially in the cooler months of the year,” said Professor Steffen.

    “Pretty much everywhere can expect to spend more time in drought. Even when average rain falls across the year, the effect of climate change now appears to be more extensive dry periods, and heavier rainfall when it comes.

    “You can take that old phrase, this is a land of drought and flooding rain, and say that climate change is going to intensify that pattern.”

    Australia is not the only country to see a drying trend.

    “There is a fairly strong drying trend in southern Africa, and there is some evidence that’s related to climate change. Drying around the Mediterranean is quite pronounced, and that’s a very consistent prediction of all the models when they are run in hindcast - when they run to see if they simulate what’s already happened. They get that pretty right.”

    However, the jury is out on the role that climate change is playing in increasing the severity of the acute drought gripping California.

    The Climate Council’s recommendation for halting the drying trend is familar and currently, politically implausible.

    “To stabilise the climate, we must rapidly reduce greenhouse gas emissions, increase investment in clean energy, and most of the world’s fossil fuel reserves – coal, oil and gas - must remain in the ground,” the report said.

    The Thirsty Country report can be read online.

    Matthew Cawood

    Matthew Cawood

    is the national science and environment writer for Fairfax Agricultural Media
    Date: Newest first | Oldest first


    David Fleming
    27/04/2015 5:04:27 AM

    Yet, there is a a high level of inaccurate short term weather forecasting. This is due to the majority of our continent being of a semi arid nature. I was taught this in 6th class. Walgett is a classic example of semi arid extremes and it's been that way for generations! The more pressure we have to provide food at unsustainable prices is the real factor behind drought. If I need only run 100 cows on "Ulah" there would be no drought here even though we have had less than half our annual rainfall for three years now, destocked last year, and five missed crop opportunities.
    27/04/2015 6:02:25 AM

    i don't want to sound like a climate change fool but remember the2ky bug, never happened. Whatever happened to those boffins that made those predictions?Nothing I assume. Same too for this summer for Victoria. The fire season was supposed to be worse than ever...turned out (thank heavens) to be kind to us. What happened to those who made predictions, i suppose nothing. Well, in the real world of small business if I made those magnitude of mistakes I would pay a financial penalty. Well, people who made these predictions should have financial implications attached to positions should they get it wrong.
    Bim Joyd
    27/04/2015 8:29:21 AM

    Why is it that nearly all the alarmist predictions come from people who work for organisations with the word "climate" in their name? Perhaps their survival makes them conflicted?
    Chick Olsson
    27/04/2015 1:44:35 PM

    Then we must invest in bringing down water from the North of Aussie if cities desire cheap and clean food
    27/04/2015 2:41:20 PM

    What happened, Shorty, was that there was a global effort to upgrade and correct computer systems, so the "bug" effect was minimised. It was a real potential problem, and it was recognised and fixed. (That's not to say there wasn't a gleeful media beat-up - but the problem was real.)
    27/04/2015 2:43:36 PM

    And on top of that, Bim Joyd, not to many of them in these 'climate' organisations have too much by way of relevant qualifications to be coming up with the predictions and alarmist theories which they arrive at. One only has to look at our history to know that at some point in the future will get plenty of any of the predictions, but by also looking at and studying our history one should easily conclude that it all happened before without the 'man made factor' so why all of a sudden is that now the cause. Why, because if man made then they can charge us for it. Scam complete.
    27/04/2015 5:19:20 PM

    If all this drought is normal why are farmers asking for handouts?
    27/04/2015 10:16:31 PM

    It seems, shorty, that you do not read the meteorologists forecasts carefully. They give a probabiiity value for each forecast They cannot say and do not say that they are 100% certain of their forecast - rather they give a percentage value for its chance of being right . You also seem to be unable to appreciate the difference between weather and climate . Climate as used by the scientist refers to long periods of time - c.15-20 yr. Weather obviously relates to much shorter time periods.
    27/04/2015 10:33:13 PM

    The Bradfield scheme and work by Professor Endisbee showed that we have much more opportunity for development and food production in Australia. Only problem is we have green interests and climate change gurus that will stop any future development of our massive resources here in Australia. These infrastructure schemes could be developed and funded like the Snowy Mountains project which will bring benefits for countless years ahead (just like the current generation is benefiting from the Snowy project). The New Asian Bank will be available to provide funding with Australian ownership.
    Eddie Randle
    28/04/2015 6:24:01 AM

    I worked and lived on Nockatunga station in the early sixties. In that time I seen the biggest drought in history. I worked and lived in Ilfracombe in the late eighties -early nineties, same story. I reckon I have seen the biggest drought in history every 6 years since. Come on it is a dry country.


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