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

    Max
    28/01/2015 6:07:00 AM

    Wow, they have come out of the woodwork now. Andrew, how can I be any more sure that your Andrew isn't an alias, means nothing to me, still to the realities we face and the main reality we are facing is the expensive scam that has been forced on us. What are the sufferings and deaths of thousands we are supposed to be promoting. It just gets more desperate and ridiculous day after day.
    FB
    28/01/2015 6:27:40 AM

    Yes Max and the scam will not only rip billions of dollars from us it will deprive millions of people from cheap and available electricity. Hence in effect making their life harder and so they die earlier in life. The AGW scam if let run its course could cost more lives than all the wars combined. This scam needs to be stopped now. The AGW scam with its insane ideas of zero carbon emissions has the capacity to plunder, enslave and decimate the human race.
    Qlander
    28/01/2015 6:46:11 AM

    Sigh... summer in Australia. All the usual pest turn up, ants, flies, mozzies, and Global Warmists.
    Mick
    28/01/2015 6:55:06 AM

    Blah Blah Blah....more bleating from The Little Children Who Cry Wolf....with stupid predictions like no more ice on the Himalayas, dams will never be filled again, the Climate Scientists getting stuck in ice near Antartica and NASA and BOM getting caught out fudging their data, it is no wonder more and more people around the world are waking up and realising that man made climate change is....well......crap.
    Sigh
    28/01/2015 7:01:03 AM

    Denying the science can have only one outcome...and it isn't good. For those of you science skeptics out there, I thank you. I will be the one buying your land real cheap from the bank in 10 years time.
    fridgimus
    28/01/2015 7:34:37 AM

    How's it feel Mick, to know little children have got more idea about what's going on with our climate than you!
    Mick
    28/01/2015 7:48:39 AM

    Sigh, you mean the so called 97% of scientists that agree with man made climate change? The vast majority that are not peer reviewed and made up of organisations such as Save the Koala foundation? The science that has been fudged by the UN, BOM and NASA? Last year in Adelaide there was 19 days over 30c...this year to the 28th there have been 10 over 30c...your so called 'science' is not backed up by 'facts'
    Old Crow
    28/01/2015 7:54:05 AM

    I can just imagine someone in medieval times who is about to be burned at the stake for denying the religion of the day being told the same thing. Sigh.
    Qlander
    28/01/2015 8:08:37 AM

    The opposite to sceptical is gullible.
    Benson
    28/01/2015 8:08:43 AM

    My God here we go again more false prophesies. I wish that climate change would turn up some heat so we can have a swim at last. We went to Philip Island in vic last week end and the bloody beach was deserted and not one single person was in the water having a swim because it was too cold and the summer season is almost over. There are no such thing as global warming scientists, there are only global warming prophets and they always get it wrong.
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