Climate change to turn up heat

27 Jan, 2015 07:08 AM
Comments
101
 
It means more occurrences of devastating weather events

GLOBAL climate is likely to become increasingly prone to extremes with super La Nina and El Nino events in the Pacific to almost double in frequency this century, according to Australian-led research.

In a study published on Monday in the journal Nature Climate Change, an international team led by the Commonwealth Scientific and Industrial Research Organisation's (CSIRO) Cai Wenju found extreme La Nina events forming in the Pacific would increase from about one in 23 years to one every 13 years because of rising greenhouse gas concentrations in the atmosphere.

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  • The work, based on 21 climate models, comes a year after a team led by Dr Cai published a paper finding extreme El Nino events would double in frequency from once every 20 years to once per decade. Total event numbers remain little changed but their intensity increases.

    About three-quarters of the additional super La Ninas would follow in the year after an extreme El Nino event, potentially adding severe strains to societies and ecosystems.

    "It means more occurrences of devastating weather events, and more frequent swings of opposite extremes from one year to the next, with profound socio-economic consequences," the paper concludes.

    The El Nino-Southern Oscillation is a major driver of climate variations. In El Nino years, the eastern equatorial Pacific warms relative to the west, slowing easterly trade winds and drawing rainfall away from eastern Australia and parts of South East Asia with droughts common.

    La Nina years involve the reverse process, with heavy rain and floods in the western Pacific but drier conditions prevailing in the east. The ocean also tends to absorb more heat during those years, placing a drag on surface warming.

    Global records count four extreme La Ninas in 1877, 1972-73, 1988-89 and 1998-99. The latter event followed a year after a super El Nino, and in the future such back-to-back extremes will double in frequency to happen every other time, Dr Cai said: "Climate change is going to increase the sequence in which you have an extreme El Nino followed by an extreme La Nina."

    The eastern equatorial Pacific – where El Ninos form – is warming faster than the western Pacific and both are heating up faster than the central Pacific.

    "In a warming world it takes smaller temperatures to generate those kinds of shifts (to either an extreme El Nino or La Nina) because the warming is not uniform," Dr Cai said.

    The tendency towards more extreme conditions has been noted in the latest climate projections released this week by the CSIRO and the Bureau of Meteorology (BoM).

    While droughts can be devastating the impacts tend to be slower to build compared with floods.

    "While wet years are typically good for agriculture and for topping up our dams, the extreme La Ninas tend to lead to more flooding and damage," said Kevin Hennessy, group leader of CSIRO's climate unit. "We find that there's a significant increase in the one-in-20 year extreme daily rainfall events right across Australia in the future."

    Dr Cai and his team noted that in the super La Nina event of 1998-99, Bangladesh suffered one of its worst floods, with about 50 per cent of the nation and 30 million people affected. China also reported floods and storms that killed thousands and displaced more than 200 million.

    The Atlantic hurricane season also tends to be more active than usual in La Nina years, as it was during the extreme event.

    Dr Cai said the modelling of extreme Pacific conditions was based on the current high greenhouse gas emissions trajectory.

    "If we do nothing, this is what happens," Dr Cai said. "It's an awful result."

    The next big area of study in the field is likely to focus on how the size of regions affected by floods and their intensity will change, he said.

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    READER COMMENTS

    nico
    29/01/2015 6:39:01 AM

    No, daw, it doesn't "boil down to conjecture" any more than any other scientific theory. The reporter gave only a hint at the detailed and complex paper, which assessed past observations and measurement, and made reasonable extrapolations from the data. The graph is going upwards, and the swings are becoming greater. There is a high probability that the pattern will continue unless it is changed by external forces. (Which reference of yours?) See:http://www.climatechangeinaus tralia.gov.au/en/about/
    Max
    29/01/2015 8:23:17 AM

    Nico just listen to yourself, "There is a high probability that the pattern will continue unless it is changed............." Unbelievable........
    Susan
    29/01/2015 11:04:40 AM

    Writers like like Benson, FB, Max & Mick can best be described as yesterday’s men -- unable to accept up- to- date data showing unequivocally that the planet is warming , Perhaps their political baggage places scientific constraints on them . Atmospheric greenhouse gas CO2 continuously increases because CO2 production rate exceeds the capacity of the planet to handle it despite some increase in plant growth . The continuous and smooth global sea level rise (2mm /yr) due ocean expansion & glacial melt shows the warming effect - see Sea-level Rise :: CSIRO & ACECRC)
    daw
    29/01/2015 12:13:02 PM

    Try looking up the meaning of conjecture in the dictionary, Nico. You'll see then that what Hennessy said is conjecture. Try reading 'Taxing Air Facts and fallacies about climate change' by Prof. Rob Carter et al ( kelpie press). A great read for people with receptive minds. Good comment Max but Nico doesn't understand the laws of motion.
    Old Crow
    29/01/2015 12:16:58 PM

    Which comic book did you get that out of, Susan?
    nico
    29/01/2015 12:35:00 PM

    Susan, it is a relief to read someone who actually understands what is going on. Max, please concentrate: I will repeat, just for you: (concentrate now): there is a high probability that the pattern (of rising global temperature and increased variability) will continue. This is not a plot. It is not a conspiracy. It is globally observed and measured fact.
    Oscar
    29/01/2015 1:19:29 PM

    nico, I don't disbelieve that climate change exists. However, I don't believe man is causing climate change, simply accelerating it. I believe it to be a naturally occuring cycle of the planet.
    daw
    29/01/2015 2:01:41 PM

    Err excuse me NIco how can 'there is a high probability that the pattern (of rising global temperature and increased variability) will continue.' be an 'observed and measured fact' when it hasn't happened yet? More conjecture perhaps?
    nico
    29/01/2015 2:02:15 PM

    Laws of motion, daw? I have not read Carter's book, but I note that he is associated with denialist groups such as the Heartland Institute and the IPA. This does not instil confidence, especially as his views have been seriously reviewed by genuine climate scientists (Carter was a mining geologist). A number of Carter's claims have been shown to be factually wrong eg "no warming for 18 years", "missing hotspot", "CO2 increase always follows warming". I'll read the book if I can get a copy. Here (for the open-minded) is a review: http://skepticalscience.com/docs/ Comments_Taxing_Air.pdf
    Gumtree
    29/01/2015 2:30:59 PM

    Carter is factually wrong eg '' no global warming for 18 years '' is he Nico ? Well TELL us Nico you keep evading this question , how much warming has there been in the last 18 years ? None. You are the one that is factually wrong and Bob Carter is correct. And to all that DO have an open mind I have read a number of Bob Carters books and I HIGHLY recommend them. I VERY much doubt Nico that you could bring yourself to read them, they would be way to upsetting for your belief system, your likely to go into a meltdown once the truth has dawned on you.
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