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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    28/01/2015 8:15:11 AM that the best you got? *laugh* You have to get your message across by fudging and manipulating data....Actually, calling you children is insulting to children, children know the difference between lies and facts. When are the Himalayas going to be ice free? Oh that is right, according to 'facts' and 'science' a few years ago! Haha
    28/01/2015 8:23:13 AM

    Global warming is a religion, it has its own prophets of gloom and doom. One main prophet is an American whom I describe as Prophet Al Gore. The other is an Australian who I describe as Prophet Tim Flannery. But there are thousands more Just like them. The religion of global warming is the only religion that forces people to pay tithes which are known in political terms as carbon tax or ETS. Skeptics - learn this fact and keep it in your minds. THERE ARE NO SUCH THING AS CLIMATE CHANGE SCIENTISTS. THERE ARE ONLY CLIMATE CHANGE PROPHETS.
    28/01/2015 8:33:20 AM

    IF Mr sigh is so sure of himself that global warming is real, then why is he thanking us skeptics because he believes that because we deny that global warming is real, he is going to be able to buy our land cheap. ? He should understand that if the land won't be any good to us ,it's not going to be any good to him either. Unless he's thinking of starting drilling for oil or something.
    28/01/2015 9:26:42 AM

    Gumtree, the whole world of science is there for you to appreciate - and yet you choose to cite a serial misrepresenter, tabloid journalist Nathan Rao of the UK Daily Express. Why? Rao has zero credibilty. Zippo, I think you are facing an uphill task, persuading Percy/Max to try and understand how science works. Rose, your assertion is a half-truth at best. A comprehensive essay on the subject is at: egreengrok/fertilizationeffect/
    Bushie Bill
    28/01/2015 10:30:48 AM

    Don't forget the whingeing rednecks, Qman, although they are around in all seasons, aren't they? Hey that is a good line I am willing to give you "RARA Rednecks; Men for All Seasons". Do you like it, Qman? Feel free to use it whenever and wherever you wish. No need ton thank me, mate. It is my pleasure to help out a sector of our society that has forever been trampled on and taken advantage of, simply because they are, um, rednecks.
    28/01/2015 11:15:33 AM

    What a doozy Kevin Hennesy "We find ....a significant increase...... in the future." Scientist or psychic?
    28/01/2015 1:38:59 PM

    You would complain, daw, if the climate researchers failed to do their job, which is to assess the evidence, measure the effects, and make informed predictions, which in turn should show the robustness of the theory. Your easy sneer at Kevin Hennessy, a Principal Research Scientist of many years experience, is not up to your usual standard. If you can refute the conclusions of the published paper, you should of course have your own work published. Have you read the paper cited?
    28/01/2015 3:45:57 PM

    Only passed the comment because it was deserved, Nico. Even the english is poor and the subject boiled down to conjecture. Try reading my reference it is a very informative and realistic treatise on a wide view of the real science.
    Beef man
    28/01/2015 11:15:05 PM

    Global boring, what was a hot dry spell called 20 yrs ago and why did the Bunbury harbour master tell me the other day that the ocean level has risen only .60 of 1 mm and these guys measure the tides it's there business.
    29/01/2015 6:20:27 AM

    But beef man you don't get it. The Bunbury harbour master is doing it all wrong. He has to homogenise these measurements first then feed this information through 20 odd models before he can possible come up with an acceptable result. Come on get with the program, don't led the faithful astray.
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