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El Nino to 'take greater toll'

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Furry Facts: El Nino and La Nina

If you've ever found it hard to understand why Australia's swings between drought and floods, help is at hand, thanks to cartoonist John Shakespeare and Science Editor Nicky Phillips.

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Australian scientists claim to have provided a clearer answer to a 20-year climate puzzle - but the finding will not be welcome news for farmers, policymakers or the wider public.

The El Nino-Southern Oscillation, which operates over the Pacific and is viewed as an engine room for driving variability in the world's atmosphere, has long been studied to understand how it will be affected by global warming from greenhouse gases.

For these sorts of changes, the signal becomes larger as time goes on under the scenarios we've used. 

New work by the Centre for Australian Weather and Climate Research, jointly run by the Bureau of Meteorology and CSIRO, shows that the impact of El Nino years - marked by a relative warming of waters in the eastern Pacific and shifting rainfall patterns - will be exacerbated by climate change.

El Nino weather patterns are generally bad news for eastern Australia.

El Nino weather patterns are generally bad news for eastern Australia. Photo: Reuters

''There's an intensification of changes in rainfall that are driven by El Nino,'' Scott Power, research leader and a senior climate scientist at the bureau, said.

Using the latest climate models, the team found western regions of the Pacific, such as east Australia, will have worse droughts during El Nino years, while the eastern Pacific will experience heavier rains. ''What we found was those two effects are intensified in the future, because global warming interferes with the impact El Nino has,'' Dr Power said, citing peer-reviewed research to be published on Monday in the journal Nature.

Wenju Cai, a senior CSIRO research scientist, said the latest study showed a stronger agreement than earlier climate models.

A satellite view of the equatorial Pacific.

A satellite view of the equatorial Pacific. Photo: NASA

The results may also show that changes in La Nina years - when western Pacific waters are relatively warm - could bring more extreme conditions to eastern Australia, he said. ''During an El Nino period, the drought in the western Pacific could be more intense, or during La Nina [ones], the floods could be more intense or maybe both,'' Dr Cai said.

While separating the impact of greenhouse gas-induced global warming from natural variability can be difficult, human influence on El Nino patterns becomes clear from the latter part of the 21st century, Dr Power said.

''For these sorts of changes, the signal becomes larger as time goes on under the scenarios we've used,'' he said.

Heat - without the El Nino

Most of the hottest years globally and for Australia have been El Nino-dominant years, such as in 1997-98.

"When the world tends to warm up because of El Nino, so does Australia,"  Dr Power said. "That's because we tend to get less rainfall, so it dries out and clouds clear, we [then] get more radiation hitting the surface, less evaporation to moderate things, and temperatures go up."

While more research is under way on El Nino periods - such as whether their frequency will change from the current three to eight years - climatologists have been surprised at the unusual heat recorded in Australia over the past year even though El Nino-Southern Oscillation conditions have remained neutral.

"It is sobering to see that we're setting these records in non-El Nino years," Dr Power said.

Record warm sea-surface temperatures and extended periods of heat over central Australia have put the country well on course to record its hottest calendar year.

A record hot summer and winter has also extended into September, which notched the biggest monthly departure ever from long-term averages for heat.

Dr Power, a co-ordinating lead author in the latest Intergovernmental Panel on Climate Change report, said global temperatures are likely to rise 0.3-0.7 degrees over 2016-2035, compared with the past 20-year period.

"The magnitude of the changes [on future El Nino periods] will critically depend on the amount of emissions that the world ultimately ends up producing over coming decades," he said.

169 comments

  • "During an El Nino period, the drought in the western Pacific could be more intense, or during La Nina [ones], the floods could be more intense or maybe both"
    Or maybe this, or maybe that, or maybe both, or maybe none. Hell we just made something up to get our names in the papers and our next study funded. Everyone knows we are hopeless at predicting the weather, but we have some of the worlds most powerful computers to play with.

    Commenter
    Gilly
    Location
    Melbourne
    Date and time
    October 14, 2013, 7:15AM
    • The world was flat once. Then someone worked and worked and worked on the evidence and found.........................................................

      Commenter
      Oh yeah
      Location
      Melbourne
      Date and time
      October 14, 2013, 7:51AM
    • Classic psychological / persuasion behaviour on display here. You have a preconceived notion of climate change and rather than pay close attention to what's said in the article, you use what's called "message distortion" to avoid being persuaded. If you re-read the article and make some attempt at finding the original source, you'll find that your comment is nonsense. Your rant exposes your ignorance and biases rather than any weakness with the authors' position.

      Commenter
      Tom
      Date and time
      October 14, 2013, 7:52AM
    • It's the tone in which conservative scientific language is written. I work outdoors, as well as commuting in the elements and I have used the BOM virtually every day for the past 15 years to assist in planning my movements. They are very accurate the vast majority of the time. People who like to claim they are not appear to have their objective reality clouded by an inherent bias against the organisation.

      Commenter
      Rob
      Location
      Melbourne
      Date and time
      October 14, 2013, 8:11AM
    • LOL, lighten up people. I was having a laugh at his language. Could do this, might do that, or this, or that, or both. Comical stuff.
      FWIW, I am not a "Climate Change" denier. Not a believer either. Totally agnostic. That wont stop the mouth frothing I guess, but it's best to know I am not against your beloved belief.

      Commenter
      Gilly
      Location
      Melbourne
      Date and time
      October 14, 2013, 8:38AM
    • "everyone knows we are hopeless at preciting the weather" - really? so when you go out I assume you dress in layers from a singlet to an overcoat, shorts under your trousers, and always take an umbrella with you, just in case.

      Commenter
      StBob
      Date and time
      October 14, 2013, 8:38AM
    • As soon as you start to see the word "maybe" in these things, you have to question the validity of the commentary. Maybe the earth will be hit by a meteorite as well - does that make it reality. If these guys want credibility they need to provide better than "maybe".

      Commenter
      TC
      Location
      Melbourne
      Date and time
      October 14, 2013, 8:41AM
    • Science is never settled.
      Look up Kepler's laws and educate yourself, the Sun is the dominant force in weather and climate.

      Commenter
      Keyboard Scientists
      Date and time
      October 14, 2013, 8:49AM
    • TC
      Obviously you have never read a scientific journal in your life.
      Scientists always talk in terms of "could" and "should" when they are predicting the future.
      Other chance factors can always come to pass. A massive volcano could change all predictions. An earthquake in Antarctica could throw millions of cubic miles of ice into our oceans.
      Only idiots talk in absolutes. But we shouldn't be letting the idiots set our policy.

      Commenter
      Steve
      Date and time
      October 14, 2013, 9:02AM
    • Gilly I experienced Global Warming where I live from 1963 to 2008. The Winters were mild and the Summer nights were HOT. I never needed to wear my winter gear. Then in 2009 the COLD winds came blasting back. GW aka CC is NOT man made it is the SUN. The changes taking place in the SUN is warming up the Planets but the GW aka CC Scientists are ignoring this in order to get more money from the Western Governments to play with their Computers. In the future the SUN will be burning searing HOT drying up the surface water. It will be then that they will be forced to acknowledge that GW is not man made.

      Commenter
      Acushla
      Date and time
      October 14, 2013, 9:08AM

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