What's driving the drought?

03 Feb, 2014 03:00 AM
Comments
22
 
The usual climate drivers aren’t in evidence... not unusually warm, not unusually cool, just average

WHEN agriculture in eastern Australia is in strife, an El Nino event is often hanging around.

This time, there is no El Nino, but the drought stress on landholders through NSW and Queensland is acute. What’s going on?

Bureau of Meterology climatologist Lyn Bettio offers two answers: “heat” and “don’t know”.

Heat, because Australia has experienced its hottest year on record, amplifying evaporation rates and minimising the benefit of any rainfall that has fallen on parched land.

Don’t know, because climate scientists are still trying to work out what’s causing the absence of rainfall over vast chunks of eastern Australia.

The usual climate drivers aren’t in evidence. Around the continent, the oceans that breed Australia’s weather are in a neutral state - not unusually warm, not unusually cool, just around average.

Unfortunately, Dr Bettio said, for reasons not yet understood, that isn’t producing “average” weather.

After a destructively wet cycle, the failure of the 2012-13 monsoon kicked off a year of hot, dry conditions - and not coincidentally, poor cattle prices.

Mt Isa recorded its driest year on record. Just 86mm fell on the north-western Queensland town in 2013.

National Climate Centre climatologist Blair Trewin reported on www.theconversation.com that for large parts of inland Queensland, 2013 was the among the driest 10 per cent of years on record.

Dr Bettio said that for NSW, the 18 months from August 2013-January 2014 was the fifth driest such period on record.

Such low rainfall is depressing, but it is within the bounds of normal variability in Australia’s naturally highly variable climate.

Temperature, on the other hand, has been well outside natural variability. Last year was the hottest year recorded in Australia, 1.2C warmer than the 1961-1990 average.

The record heatwaves of early 2013 and 2014 made the news, but the more exceptional conditions were recorded in September, when Australian temperatures were 2.7C above the mean.

As Dr Trewin and other climatologists wrote on The Conversation, September 2013 temperatures were those of an average November.

Dr Bettio said these figures are in agreement with other temperature trends from a warming world. What’s less clear is temperature’s relation to rainfall in northern latitudes.

In south-eastern and south-western Australia, climate models show a clear signal between rising temperatures and decreased rainfall over the long-term.

Over northern NSW and southern Qld, that clarity isn’t there.

That makes it difficult to point to a culprit behind the current drought, Dr Bettio said. And without a culprit, it is impossible to forecast when drought might abate.

Ex-Tropical Cyclone Dylan, which crossed the Queensland coast near Bowen on Friday morning and weakened into tropical low, offers some promise of breaking the cycle, but that promise has been extended before, and not delivered.

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READER COMMENTS

shorty
3/02/2014 5:00:45 AM

Why choose a 40 year average on temperature? Why not an average since records began? Please, we need the clearest picture available!
Qlander
3/02/2014 7:45:44 AM

Wow! What a refreshing change, a climatologist who admits she 'doesn't know'. There might still be hope for the future of climate science.
bg
3/02/2014 3:09:24 PM

Shorty. The average temp since records began will be lower than the 40 (really 30) year average used. That's because the recent average excludes the lower temperatures in the early 1900s. As we warm up, the average also goes up (at a much slower rate). 1.2C above the 1960-90 period relates to something like 1.5C above the 1910-1940 period.
nico
3/02/2014 4:28:01 PM

Your comment, Qlander, shows a sad failure to understand science. It is *because* scientists don't know that they continue to do their research. Not knowing is a given. Meanwhile, there are contributors to this forum who regularly sneer at the normal scientific practice of expressing degrees of probability, rather than making statements of certainty. It is reasonable and normal for a scientist to accept a theory as proven, especially if it is based on empirical evidence, but to say "probably" in particular circumstances, such as causes of the present drought.
Sodbuster
3/02/2014 6:30:15 PM

via nico: "It is reasonable and normal for a scientist to accept a theory as proven, especially if it is based on empirical evidence" The global warming hysteria is based on models. The models claimed the planetary climate would be warming. It hasn't for over 15 years = no "empirical" evidence for proof of claim. What we have had is warming from coming out of the last mini ice age. This was identified well before the global warming claims/Hysteria. (if link dont work check for spaces) http://jonova.s3.amazonaws.com/sh 1/the_skeptics_handbook_2-3_lq.pd f
argis
3/02/2014 7:38:59 PM

What about Australia's worst ever heat wave in 1896? Check the records out.
Ted O'Brien.
3/02/2014 8:50:11 PM

Two things I noticed happening. Southerly changes that used to come via SW Australia started coming more directly north via Adelaide or even east of there. Jet trails which normally move here from west to east, sometimes slowly, sometimes quickly, about 14 months ago spent a lengthy period either moving very little, or even on occasion moving from east to west. I have never seen that happen before. Also, big rainfall events in NW Australia used often to bring good rain to central and eastern Australia. Now they head south. We did still get rain sometimes.
Ted O'Brien.
3/02/2014 9:01:00 PM

nico, You have discovered the word empirical. Now you must understand that there is nothing empirical in a computer model which operates on guesswork. Especially so when the input data is "adjusted".
Shazz
3/02/2014 9:33:51 PM

They say things like "It is the hottest day on record in 100 years" what caused the heat wave 100 years ago?? Rather arrogant of us to think we are big enough and important enough to effect something as huge as universal climate. Some questions I have are 'what caused the ice age?' and 'why did it start melting?' Could it be that the universe is a constantly evolving organism and humans and animals will evolve with it?
Ranger
3/02/2014 9:37:36 PM

Thanks nico, It takes Uneducated idiots to challange SCIENCE. Have a look at our present PM. He does not trust or believe in SCIENCE
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