El Nino taunts, records tumble

08 Dec, 2014 03:00 AM
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The testing conditions for agriculture show no signs of going away

IF it feels like an El Nino, and looks like an El Nino, are we in an El Nino?

Technically, no, but to all intents and purposes the effects that might be expected of the climatic event appear to be at work across most of the countries it affects.

“We’ve got factors that are close to the thresholds for an El Nino,” says the Bureau of Meteorology’s (BoM) manager of climate prediction services, Andrew Watkins.

“Last week was the first week since March 2010 that the Pacific was a degree warmer than normal. So it’s the first time since the previous El Nino that the Pacific has been as warm as it is now.”

Problematically, though, the signals don’t yet fit into the box of criteria that BoM uses to officially call an El Nino. If a full-blown El Nino is recognised, it signals that the pattern is typically locked in until at least the following autumn.

“It’s a weird one,” Dr Watkins acknowledged.

“The Southern Oscillation Index (SOI) has been at El Nino-type levels now for three months, and ocean temperatures have been at El Nino levels for almost a month now. And yet, we’re not seeing the rainfall, cloud or wind patterns that you would normally expect to go along with that.”

“As climatologists, we’re trying to nut out whether these things really are coupled - whether we really are locked into an El Nino until autumn, or something else is happening.”

“We’re saying there is a 70 per cent chance that it will lock in, but even though the classic signs are there, something is going on that’s a bit atypical.”

The global picture

But the current pattern 'quacks' like an El Nino, with countries usually affected by the event reporting climate patterns typical of one of the planet’s most unwelcome climate phenomena.

It’s dry in South Africa and across south-east Asia - and across much of eastern Australia. It’s wet in Peru, while Buenos Aires has reported its wettest year on record.

Unfortunately for drought-stricken California, one of the atypical signals arising from the current pattern is that the western United States is not receiving the above-average rainfall it can expect under an El Nino.

And if it is an El Nino, Dr Watkins said, “it’s very, very late”.

“The latest one we know of was in 1986, and that developed in November. For one to come to fruition in December is out of the box.

“It’s a very unusual event. Clearly there is more at play than the canonical buildup of an El Nino, and it’s a very tricky one for meteorologists to play.”

Ultimately, Dr Watkins said, current reality is more important than parameters when climatologists need to identify a climatic event.

“Things happen during the build-up stage to an El Nino, and you see impacts before we can say it is locked in until the following autumn.

“About July, the Indian Ocean was favouring rainfall in a negative Indian Ocean Dipole pattern. As soon as that stopped, so did the tap.”

Global warming may also be adding noise to the signals that climatologists use to call an El Nino event.

“There has been half a degree of warming in the central Pacific over the past 50 years, and that makes things tricky when we’re using simple boxes to make an estimate of when an event is on or off.

“It doesn’t make it any easier to make the judgement calls.”

Weather records broken

The 2013 record for Australia’s hottest spring only lasted a year. The 2014 spring has broken the year-old record, and pushed out the reference point for spring heat by a substantial margin.

At an average temperature of 24°C, the BoM reported spring 2014 was warmer by 1.5°C than springs through the reference years 1961-1990, a big jump in climatic terms.

Record warmth introduced a vicious cycle around the soil moisture deficits afflicting much of eastern Australia.

With no moisture in the soil to provide evaporative cooling, atmospheric temperatures jumped, in turn ensuring that any of the sparse rainfall that fell on parched soils was more rapidly lost to evaporation.

The testing conditions for agriculture show no signs of going away.

BoM is forecasting that nowhere across the eastern two-thirds of the continent is there a better than 40-45 per cent chance of exceeding median rainfall out to February.

For most areas, the odds are less than 40pc, and for large swathes of inland Queensland, less than 30pc.

And with no topping-up of dry soils, temperatures seem likely to remain unrelentingly warm.

The chances of exceeding the median maximum temperature through to February are above 60pc for all of the eastern two-thirds of the continent, BoM estimates, and above 75pc for regions of western Queensland and northern NSW.

The persistent resetting of temperature records is in line with predictions for global warming.

Early last week, the American Geophysical Union reported that melting rates in western Antarctica have tripled in the past decade.

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FarmOnline
Matthew Cawood

Matthew Cawood

is the national science and environment writer for Fairfax Agricultural Media
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READER COMMENTS

Frank Blunt
8/12/2014 8:50:37 AM

And fortunately we have that extra little bit of CO2 in the atmosphere which will help plants with any drought conditions.
Qlander
8/12/2014 9:40:39 AM

Yep, making forecasts within the time frame of your career, is a tough gig. Safer to stick to what will happen after you've retired/died.
Selector
9/12/2014 9:01:03 AM

Are the temperature records reported actual or BOM adjusted and if adjusted what is the difference?

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