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

    Gumtree
    9/02/2015 1:06:38 PM

    It would help, Nico, if you get your information from a reliable source. The sources you use have been caught out lying and manipulating the data and you wonder why your/their reputation is totally shot.
    daw
    9/02/2015 11:30:49 AM

    / cont No one to date has been forhcoming with proof.
    daw
    9/02/2015 11:22:29 AM

    Yes Nico I probably can but it was good enough for you to comment on. The emails, whether stolen or leaked, tell a strong story of collusion to deceive & corruption of the scientific method of peer review. They also discuss the contentious issue of 'does CO2 explain why warming is taking place'. Malcolm Hughes replying to Tom Crowley's question. 'So, are you sure that some carbon dioxide effect is responsible for this? May we not actually be seeing a warming?' says 'although a direct carbon dioxide effect is still the best candidate to explain this effect, it is far from proven.' /cont
    Billy
    9/02/2015 11:02:04 AM

    Its not me that is ignoring the temperature data, Nico, it's you. You make a big song and dance about a half a degree of warming over the last 150 years and then try to tell us all its the end of the world when in fact the warming is good, and you wonder why no one takes you seriously. Are you seriously going to try to tell us that cooling is better ? You should not get your information from denialist blogs Nico and use your brain and commonsense just for once. I know this is a challenge for you. Can you tell us what the benefits of living in a cold climate are?
    nico
    9/02/2015 7:34:27 AM

    Please, daw, you can do better than that. Let me remind you: a thousand or so emails were stolen, and a few sentences were quoted, out of context, to try to prove a conspiracy. (The theft of the emails certainly revealed something else that was nasty.) A series of high level inquiries showed that the scientists involved were guilty of nothing more than using strong language in supposedly private correspondence. And no one is asking you to "believe" anything - just to get your information from a reliable source.
    daw
    6/02/2015 1:46:31 PM

    For goodness sake stop your preaching will you Nico. The debate is supposed to be about climate change. Comply with your own sermons telling people how to stick to the topic & 'ignore the yapping'. By the by Science is about experimentation, measurements within the experiment, observation and recording of ALL results as found, not just the bits that agree with your thoughts and hypothesis. Sadly the lead scientists involved with climate change studies, some years ago, corrupted the peer review process as shown in the 'climategate' emails scandal. Good reason for us to not believe them.
    nico
    6/02/2015 1:12:43 PM

    Billy, no, I don't believe you when you say that you know what you are talking about. You ignore the observed, recorded and freely available global temperature record. Referring to "the science fiction that the CAGW people peddle" is particularly offensive when you offer nothing more than your opinion. For an overview of the past two millennia, see:http://thinkprogress.org/clim ate/2013/07/08/2261531/most-compr ehensive-paleoclimate-reconstruct ion-confirms-hockey-stick/
    Black Stump
    6/02/2015 11:28:24 AM

    I think Billy might be right, Nico, temperatures have been going down for 8000 years since the Holocene climate optimum , the tiny rise last century was just a little blip on a downward trend. Unless of course you can prove otherwise the long term trend is down not up as you keep stating and is well accepted history.
    Billy
    6/02/2015 9:57:28 AM

    Believe me, Nico, I do know what I am talking about and I am quite up to date with my reading. My science teacher would be proud that I understand real science and history and not sucked in by the science fiction that the CAGW people peddle.
    nico
    6/02/2015 8:46:35 AM

    Billy, it seems that you don't quite understand what you are talking about. Science is not about belief. Science is about observation and measurement and explanation. Using words like "stupid" and "gullible" and "crap" and "DUMB" simply shows that you have not bothered to keep up with your reading. Your science teacher would be shocked by your dismissive attitude (and by your manners.)
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