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

    Percy
    27/01/2015 10:26:15 AM

    What! ; more floods? Flannery told us that that dams were never going to fill again so the Labor Brumby government built a great white elephant called a desalination plant, put in a north south pipeline stealing water from rural Victoria (and South Australians). I do wonder whether these so called experts who make up computer models realise that they only predict from inputed data which is guesswork on behalf of the modeller (garbage in = garbage out). Have they made any allowances for nature to compensate from the extra growth producing carbon dioxide in the atmosphere over the 100 years?
    Max
    27/01/2015 11:47:52 AM

    Spot on Percy. And I see it has taken 21 climate models for them to come up with this latest lot of guess work. You can only get out what you feed in.
    booj IQ
    27/01/2015 5:32:42 PM

    Learn all about Climate Change in a 2 minute Video: http://bit.ly/1zy4div
    Andrew Roberts
    27/01/2015 5:46:40 PM

    Percy, you refer to ancient history... they were ahead of their time... What are you thinking Gina Rinehart and other Mining investors... did you not think it (Globalisation) would all come back to Australia as CO2 and cheap imports (waste)? Faster than any model predicted! You are right about garbage Max, Australia is receiving more than its share of the garbage it has put in. Especially from anonymous Max and Percy. Face us, cowards, as real Australians! Do not hide behind aliases - because you promote suffering and death for thousands.
    Harry
    27/01/2015 8:08:55 PM

    Max and Percy...are you Liberal voting old white men? I bet you are. The principles of cause and effect dictate that annually pumping billions of tons of anything into the atmosphere will have an effect. Here it is. With respect .....Duhhhhhhh......
    Zippo
    28/01/2015 2:21:16 AM

    Clearly concerning. It's past time we began taking steps to respond to the science. Malcolm Turnbull please take over from bumbling Abbott. Percy/Max - please try to understand the way science works.
    Gumtree
    28/01/2015 5:16:24 AM

    But as we all know the truth is some what different. http://www.express.co.uk/news/nat ure/554183/Britain-red-alert-disp laced-Polar-vortex-unleash-weathe r-hell-next-week
    Gumtree
    28/01/2015 5:29:41 AM

    And more. http://www.infowars.com/forecaste rs-fail-on-blizzard-yet-were-supp osed-to-believe-100-year-climate- models/
    Old Crow
    28/01/2015 5:34:16 AM

    Andrew, Harry and Zippo, the 3 stooges.
    Rose
    28/01/2015 5:59:24 AM

    Your partly right Harry. The carbon dioxide we pump into the atmosphere is making earth's biosphere GROW as carbon dioxide is the gas of life and all plants thrive on it.
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