Extreme La Niña events that affect weather conditions on both sides of the Pacific will almost double in frequency as the climate warms, reports a new study by an international team including Australian researchers,
.In Australia, La Niña is associated with flooding, and was linked to the Queensland floods in 2011 that left at least 38 people dead, affected about 70 towns, saw the evacuation of thousands of residents and hit the economy by about $30 billion.
The finding, by an international team including Australian researchers, is published today in Nature Climate Change.
Lead author Dr Wenju Cai, chief scientist at Australia’s CSIRO Oceans and Atmosphere Flagship, says their work shows La Niña events will occur every 13 years compared with a past frequency of one every 23 years.
During typical La Niña events, the central-to-eastern equatorial Pacific is colder than normal, inhibiting formation of rain- producing clouds there, but enhancing atmospheric convection and rainfall in the western equatorial Pacific.
An extreme La Niña is defined as a cooling in the central Pacific that is greater than 1.5 degrees Celsius cooler than normal average temperatures.
This increase is driven by increased land warming relative to the ocean and an increased frequency of extreme El Niño events, Cai says.
While Cai says extreme La Niña events tend to occur after an extreme El Niño because the El Niño events counter-intuitively aid the cooling process in the central Pacific.
“In an El Niño event the heat in the upper ocean tends to release to the upper atmosphere [so that] the cooler water at the ocean’s sub surface is more easily brought to the surface and [therefore it is] easier to generate cooling in the central Pacific.”
The work follows on from a study by the same team last year, also published in Nature Climate Change, which showed a doubling in “super” El Niño events.
This latest study begins to fill the gap in understanding what will happen to El Niño’s counterpart La Niña.
“This issue of how La Niña/El Niño will respond to climate change has been challenging scientists for the past 20 years,” he says.
To assess the potential future pathway for La Niña the team used 21 global climate models that were able to simulate extreme La Niña events.
The study covered 200 years from 1900-2005 and then 2006-2099 and used historical data in the first period and then the Intergovernmental Panel on Climate Change forecasts on greenhouse emissions growth for the latter period.
The study resulted in 2100 years of virtual climate with only four of the 21 models not predicting an increase, says Cai.
“The inter-model consensus is very strong,” he says.
The team also finds approximately 75 per cent of the extreme La Niñas will occur immediately following an extreme El Niño event.
The implication of this is that weather patterns will switch between extremes of wet and dry
The onset of the Great Depression in 1929 was the beginning of the decline in the boom years for Beerburrum. Farmers were unable to run a viable business or sell their property and many walked off their property destitute.
Spanish immigrants arrived in the region and were allocated settlements and grants to clear virgin bush and grow tobacco. Just when the leaves were to be harvested a fungus attacked and destroyed the crop. Once again growers walked off the land.
The ex-servicemen and Spanish tobacco growers who failed to meet the Government settlement requirements were re-possessed for the State re-forestation programme.
Go to any of the ‘Look-outs’ and as far as the eye can see there are regimented plantation of slash pines taking over the flora and fauna that once flourished on settlements cleared with ‘blood and sweat’.
Never-the-less, the pineapple growers persevered through the hard times and in 1947 formed themselves into a company to build The Golden Circle canning factory. (conclusion}
Issued on 20 January 2015 by BOM
Since late 2014, most ENSO indicators have eased back from borderline El Niño levels. As the natural seasonal cycle of ENSO is now entering the decay phase, and models indicate a low chance of an immediate return to El Niño levels, neutral conditions are considered the most likely scenario through into autumn.
Central tropical Pacific Ocean surface temperatures have fallen by around half a degree from their peak of 1.1 °C above average in late November. Likewise, the Southern Oscillation Index has weakened to values more consistent with neutral conditions, while recent cloud patterns show little El Niño signature. As all models surveyed by the Bureau favour a continuation of these neutral conditions in the coming months, the immediate threat of El Niño onset appears passed for the 2014–15 cycle.
One of Beerburrum’s most colourful tradesmen was the butcher in Anzac Avenue with the name of Dave Morecroft. The story goes that a local settler’s wife was in the habit of letting the family’s blue cattle dog enter the butcher shop and urinating on the butcher’s block, sawn from a large brush box tree. Dave warned the lady on numerous occasions that it was a serious offence to allow a dog into the shop and if continued he would not be responsible for his actions. The customer took no notice of the warnings. It was not long before she allowed the dog to go in and once more cock-a- leg against the butcher’s block. Dave grab’s the dog and with two deft blows of a meat cleaver, produced the only cattle dog at the settlement with two square ears.
Another of Dave’s customers had run up a substantial account for meat, payment was not forthcoming, even though Dave knew he could afford to pay up. Seeing him in Anzac Avenue opposite the shop one day, Dave, with meat cleaver in hand races across the street and holds the cleaver against the debtor’s ear. The dog’s square ears were a constant reminder that Dave’s threats were not to be taken lightly and the debtor paid up on the spot. (to be continued)
Following the government decision not to proceed with building a canning factory many pineapple growers walked off their property , while others were more enterprising and grew alternative crops. For instance there is the story of one settler, asked to experiment in the suitability of growing groundnuts on his property was given six sacks of peanuts to sow. Due to a shortage of peanuts the price was high and the settler could not resist the temptation for some quick cash flow. After selling the seed peanuts at market he had to explain to the departmental officers come to inspect his crop that the bandicoots had eaten the lot!
During this time the township of Beerburrum grew and became prosperous and supported not only a railway station, State Primary School, Boarding House, Public Hall, General Store, Post Office, Barber Shop, Bake House, Butcher, Cobblers and Blacksmith shops.
I wonder why a town that spells ‘beer’ at the beginning and ‘rum’ at the end had no hotel for the thirsty ex-servicemen ‘diggers’. Beerburrum is an aboriginal name meaning Place of Parrots.
Anzac Avenue became the main shopping area adorned with white painted, post and rail fence and water troughs for the numerous horses that provided the basic means of transport in those days. In 1918 a number of Camphor Laurel and weeping fig trees were planted in the Avenue to commemorate the fallen in World War One. ((to be continued)
Walking down Anzac Avenue, Beerburrum and talking to locals I found it hard to imagine this wide quiet residential road, with its splendid avenue of trees down the centre, was once the main street of a busy and bustling country town.
It all started during World War 1 when the Government of the day decided the area would be suitable for small scale farming with its rich sandy soil and subtropical climate.
‘Diggers’ returning from Flanders shell shocked and wounded were rehabilitated in a new hospital constructed on a high knoll overlooking Anzac Avenue.
Over 500 selections of varying acreages had been surveyed and were offered to ex-servicemen by ballot. A pick of a marble decided the location and acreage for the settler.
The government provided basic tools including a spade a wheelbarrow and a long crow bar for clearing the property of scrub. Pineapples were to be the first crop with a promise of a guaranteed market at a canning factory to be built in Brisbane in time for the first harvest in three years time. However, a change of Government and plans for the canning factory were dropped. (to be continued)
Copyright © 2015 Maleny Weather - All Rights Reserved
Powered by WordPress · Atahualpa Theme by BytesForAll