Pacific shift may accelerate warming

30 Dec, 2014 08:20 AM
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26
 
This could be the start of another ramping up of warming

WITH 2014 likely to be declared the world's hottest year on record, the last thing the planet needs is a climate shift to turbo-charge the global warming already under way.

While it's an early call, a measure of surface temperature differences in the Pacific shifted to a positive reading in the five months of November, according to the US National Oceanic and Atmospheric Administration – the longest such run in almost 12 years.

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  • Known as the Pacific Decadal Oscillation, the El Nino-like pattern typically lasts 15-30 years and is understood to operate as an accelerator on global surface temperatures during its positive phase – and a brake during its negative phase – as the ocean takes up fluctuating amounts of the extra heat being trapped by rising greenhouse gas emissions.

    "It certainly could be an early sign of a change but you'd probably want to see another year or two before it's a genuine phase shift," Matthew England, a professor at the University of NSW's Climate Change Research Centre, said. "This could be the start of another ramping up of warming."

    The last positive phase of the PDO, also known as the Interdecadal Pacific Oscillation, ran from about 1978 to 1998, a period of a rapid increase of surface temperatures. Since then, temperature increases have flattened out, despite an increase in greenhouse gases, as oceans have taken up more of the excess heat.

    Even with the negative-PDO drag - worth about 0.2 degrees in global average air temperatures a decade - 2005 and 2010 both topped the 1998 record annual global temperatures. The first 11 months of 2014 were the warmest on record and with ocean temperatures remaining exceptionally warm, this year is very likely to set a fresh high, according to NOAA, the Bureau of Meteorology and other agencies.

    In positive-PDO periods, the tropical Pacific is relatively warm and north of about 20 degrees latitude, it should be cool, said Shayne McGregor, a UNSW research fellow, said: "It's definitely consistent with what we've seen in tropics."

    "During a positive PDO phase, you'd expect temperatures to keep climbing again as they did in the 1980s and 1990s," Dr McGregor said, adding that as PDOs are measured by rolling 11-year averages, it will be a while before any shift becomes clear.

    Cai Wenju, a principal scientist with the CSIRO, agreed it will take time before any index shift is clear. Still, the next positive phase would likely bring faster warming at the surface and worsening drought conditions for Australia and much the region, he said.

    "When it is positive, it tends to give us less rainfall because convection is shifting away from the western Pacific," Dr Cai said, adding that floods worsen in Ecuador, Peru and elsewhere on the Pacific's eastern rim.

    While 0.2 degrees either way can set new global records or stall the march higher of surface temperatures – about 0.05 currently separates the five warmest years – over the longer term, global warming will swamp even interdecadal fluctuations, Professor England said.

    "If we stay with relatively flat temperatures for another five years, it means nothing for global warming projections for the end of the century," Professor England said, noting temperatures may then be 4-7 degrees hotter on current greenhouse gas trajectories.

    "The chance of that tiny 0.2-degree decadal signature overwhelming the greenhouse warming becomes vanishingly small."

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    READER COMMENTS

    Ian Em
    30/12/2014 9:43:52 AM

    Whoever is pumping chemicals into the sky from planes needs to be stopped. It's like an open secret, everyone has seen a chemtrail and the open agreement that geo-engineering is being implemented. Why can't we talk about why this is happening? No snow in the alps? I've got a lovely christmas photo of the alps with chemtrails right above them.
    Qlander
    30/12/2014 11:31:56 AM

    if, may, could, likely, possibly.
    pete t
    30/12/2014 11:54:15 AM

    The planet has been experiencing change since the begining of time. Believe it or not there was crocodilians in the arctic circle a long time back. We all need to reduce our ecological footprint and embrace the change. Tripping out about water vapour condensing due to localised pressure/temp variance behind aeroplanes ain't helping one bit.
    Rational
    30/12/2014 12:10:11 PM

    No one is pumping chemtrails into the sky from planes, there are prefectly logical, scientific reasons and evidence for them, just a google search away. If you don't believe facts, well there is not much hope for you and your echo chamber.
    Gumtree
    30/12/2014 12:16:35 PM

    This article is so full of fallacy its hard to know where to start with it. For a start the hottest year in what record Peter, how long is your record? A hundred years is not a very long record. Its one millisecond in recorded time. And how much has it warmed in your recorded time? The amount is so small most modern thermometers can't even accurately read it. So that blows the whole alarmist article right out of the water before we even get to second base. Second.What would it matter if it did warm a small fraction, it would not. Warming is good. So why Peter, Rabbit on and on and on about it?
    Jack Williams
    30/12/2014 12:24:49 PM

    Mr Em pollutes this article with utter garbage. A reasonable article, but Mr Em tries to hijack it with his conspiracy theory.
    DavidSG
    30/12/2014 12:38:20 PM

    The chemtrail conspiracy is most popular among those familiar with the New World Order and who claim that the spray is designed to pacify populations, either by making them sick, or some sort of mind control. Like many other pseudoscientific terms, earnest use of the word "chemtrails" immediately identifies the person using it as a crank, and is enough to harm credibility and provoke ridicule among those of a more rationalist disposition. http://rationalwiki.org/wiki/Chem trails
    Wayne S
    30/12/2014 1:33:16 PM

    All this talk about climate change and what is causing it, is a lot of crap. Has anyone thought anything about all the oil and gas that has been pumped out of the ground. I think that it's all down there to keep the planet cool, and by pumping it out the heat from the core is making the earth hotter. STOP pumping gas and oil out and find something else to drive our machinery.
    SD
    30/12/2014 2:19:22 PM

    I assume Peter is talking about world temperatures, not just Australia's and considering how the gatekeepers [Hadley, NASA, BoM etc] have been adjusting, homogenising and altering temps over the period of the pause/cooling this century awa cooling the old records, if not wiping them out completely, the whole exercise this century can only be compared to that other dubious exercise of last century ,AKA the "hockey stick" which becomes less likely with age. Not only is the science of AGW becoming less settled but the noise is becoming ever greater than the signal.
    Matti
    30/12/2014 9:16:21 PM

    "The last positive phase of the PDO, also known as the Interdecadal Pacific Oscillation, ran from about 1978 to 1998, a period of a rapid increase of surface temperatures." There we have it. We have identified the cause of recent global warming, ocean cycles, not CO2. Thank you. The planet cooled between 1940 and 1978, then warmed from 1978 to 1998, just as the article states, with the empirical evidence being that this was caused by ocean cycles.
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