Climate change to turn up heat

27 Jan, 2015 07:08 AM
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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

    Black Stump
    11/02/2015 10:29:24 AM

    Well said, Gumtree. Not to many of the faithful global warming loons protecting the faith here today. I would say Rasmuncher has gone the way of Susan and Jeffito. Back to kindi.
    Gumtree
    11/02/2015 7:46:52 AM

    It looks like Rasmuncher is still stuck in his armchair , (no surprise though, eh?) He obviously has not stuck his head out of his window for a very long time. So the whole climate debate is down to two sides. The intelligent logical thinkers who can see right through the shonky science and the climate scam. And on the other side we have the idiot brigade CAGW climate nutters who can't even answer the most basic questions and the just post total nonsense that a 9 year old can see through. If this is the best you cranks can come up with its no wonder people laugh at you and think your loons.
    Black Stump
    10/02/2015 4:41:20 PM

    Hahahahahaha Laughable rubbish, Nico.
    nico
    10/02/2015 12:23:03 PM

    You assume, daw, that I did not read the stolen emails. Of course. I didn't read all thousand-and-something of them, (did you?) but enough to form a judgement. More significant, I have read the judgement of six inquiries which found no scientific malpractice, just a beat-up by denialists. The warming effect of CO2 is familiar basic physics. A good summary, with links to original material, is here: http://www.ucsusa.org/global_warm ing/solutions/fight-misinformatio n/debunking-misinformation-stolen -emails-climategate.html#.VNmDXiz dMdU
    daw
    10/02/2015 10:37:43 AM

    Wrong Nico the emails do show many facts about the behaviour of a group of scientists behaving badly. Why are you commenting when you haven't read them? You don't have to read all the leaked emails just some of them gives a clear enough picture of the skulduggery, confusion and inappropriate behaviour that went on. How about you respond to the question of proof that co2 is responsible for the warming. Who has done any scientific experimentation that demonstrates that 400 or 500 ppm of CO2 is capable of raising the temp by 1 or 2 or as many as 6 degrees predicted by some computer models?
    Black Stump
    10/02/2015 6:00:02 AM

    Clean up the atmosphere of what Rasmuncher? Surely you don't mean clean up the carbon dioxide? So you want to take away the air that plants breath do you Rasmuncher? Then all the plants will die and then all the other life would die, that would be very dumb wouldn't it ? Then again I am getting used to very dumb comments here from the CAGW climate dummies.
    Gumtree
    10/02/2015 5:47:34 AM

    Time to get out of your armchair, Rasmuncher, 95% of the those with a brain realise there is nothing wrong with the climate and its better if it stays warm and would be a disaster if it starts to cool.
    Old Crow
    10/02/2015 5:32:27 AM

    What will I see If I poke my head out the window Rasmuncher? Oh I know, I nice warm planet and its plant life growing better by the day from rising atmospheric carbon dioxide. Why would you complain about that?
    Rasmuncher
    9/02/2015 6:08:18 PM

    Of course some uneducated armchair cowboy knows more than 95% of the world experts on climate patterns. However, one merely needs to poke your head out of the window to see that they are wrong. I am going with the philosophy that if we do nothing and it occurs we will be worse of if we do something and it doesn't. The worst outcome will be we have cleaned up the atmosphere.
    nico
    9/02/2015 2:30:29 PM

    No, daw, the stolen emails do not tell any such story. A number of inquiries found nothing more serious than some inappropriate language in what was private correspondence. Only a committed denialist would still believe this manufactured slur. As I said, you could do better, perhaps by providing real scientific evidence (which to your credit is quite beyond many of the contributors to this forum.)
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