Ice core data research flips drought risk

Climate data gleaned from deep within 2000 year old Antarctic ice has revealed that Australia's drought risk is far worse than previously thought.

The research points to future drought periods that could be nothing short of "catastrophic" for catchments in eastern Australia, according to lead scientist Dr Anthony Kiem from the University of Newcastle.

He was one of a team of researchers that looked at 150 years worth of data measuring changes in the weather and ocean across the Pacific, known as the Interdecadal Pacific Oscillation (IPO) climate variability index.

The IPO controls drought and flood risk across eastern Australia over periods of about a decade, switching between negative values that cause a wetter climate, and positive values that cause a drier climate.

The scientists then examined 2000 years of climate records taken from Antarctic ice cores, and used them to reconstruct changes in the IPO over time.

The data from the ancient ice samples led to a very different set of numbers - and some worrying conclusions.

It showed that wet periods were much shorter and less frequent than previously thought.

It had been assumed that the IPO flipped from wet to dry and back again about every 15 to 30 years, but the new data shows that wet phases last only about seven years on average and only happen about 10 per cent of the time.

The dry spells, on the other hand, last an average of more than 60 years.

"This could be catastrophic for almost all catchments in eastern Australia, which rely [on wet periods] to recharge river catchments and reservoirs and restore soil moisture after drought prone periods," Dr Kiem said.

The difference was likely due to an unusually long wet period between 1947 and 1976 - when most of the water infrastructure on the east coast was planned or built.

This had likely skewed scientists' expectations of how much rainfall and runoff to expect, according to Dr Kiem.

"This has serious implications for drought and flood risk assessments, which should be re-calculated to account for positive, dry IPO phases being the norm, and much more likely than suggested by the last 150 years of observations," he said.

Scientists from the Australian Antarctic Program Partnership and the University of Newcastle conducted the research, which is being published in the journal Communications Earth and Environment.