Climate change to turn up heat

27 Jan, 2015 07:08 AM
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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    5/02/2015 1:22:02 PM

    Temperatures have been trending down for 7000 years ever since we came out of the last ice age and back into another ice age we will go. Anyone stupid enough to believe the man made global warming crap deserves to be scammed. Its really hard to believe how gullible people are. Idiots here that crap on day after day about man made global warming and CO2 being a pollutant are either in on the scam or just totally DUMB!
    5/02/2015 11:06:01 AM

    A person who habitually denies, in the face of evidence, may reasonably be called a denialist. Stump, a good question that has been answered many times at great length. I suggest you try Google. For starters, look at jet stream perturbation, bush fires, insect vectors, crop adaptation. We have evolved, globally, to fit into our environment. We change it at our peril. See: 057-global-warming-effects.html
    5/02/2015 8:48:15 AM

    Nico, calling people denialists or neanderthals is very derogatory and is definitely not nice and not courteous. You may want to re-evaluate your last post.
    Black Stump
    5/02/2015 8:23:00 AM

    What's wrong with warming temperatures Nico, I am no expert but I would have thought they would be far more preferable than cooling temperatures. I mean its not like they have warmed much, under 1 deg C I believe in the last 150 years, and I could not even imagine would have happened if in the last 150 years it had cooled 1deg C, I think we would be in real trouble trying to grow food if that had of happened so I don't really understand your concern. A warm world is far better than a cold world is it not? Cold is a real killer and did you really think the temps would always be stationary?
    4/02/2015 1:22:40 PM

    I admit to being baffled, daw. The reference I gave was to a web page full of graphs (giss/nasa), all with variations, all with uincertainty bars. They include surface air temps, met. stations, high and low latitudes, N and S hemisphere temps, all trending steadily upwards. I answer questions quite happily (unless they are meaningless) by referring the questioner to an authoritative source. And in contrast to some of your fellow denialists, I try to remain courteous.
    4/02/2015 12:47:32 PM

    Nico, you won't answer questions, you can't read graphs, you pass commentary about scientific publications you admit to not having read. Is there any wonder so many posts here are critical of you and your crazy comments. The graphs mentioned above are not rising. I'd suggest you turn them up the right way before looking at them. Whilst you don't hesitate being critical of others you don't like it when someone criticises you or your comments. That's what many refer to as hypocrisy. If you don't like it you can always elect to join Susan.
    Old Crow
    4/02/2015 12:12:56 PM

    Awwww don't go Susan. We did not mean to hurt your feelings. You're a big girl aren't you?
    4/02/2015 11:00:55 AM

    Snappy Snappy. Susan and Nico both respond the same way when they can't answer simple logical questions, which just further shows up who the scammers and charlatans really are, obviously on the gravy train with their snouts well and truly in the trough.
    4/02/2015 10:49:26 AM

    Don't be silly Susan, no one is saying the overwhelming majority of climate scientists are charlatans and no one is silly enough to believe the overwhelming majority of climate scientists believe the discredited CAGW view that all warming is human induced or bad. Your a hopeless debater, Susan, and off you go then in a huff. Bye.
    4/02/2015 10:12:22 AM

    Obviously you have never bothered to contact those CSIRO scientists yourself, Susan. Goodbye.
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