Longer, drier "mega-droughts" to be a fact of life as global warming increases

Mega-droughts — droughts that last two decades or longer — are tipped to increase due to climate change, according to University of Queensland-led research.

Published in Nature Scientific Reports, research findings suggest climate change will lead to increased water scarcity, reduced winter snow cover, more frequent bushfires and wind erosion.  

The results were derived from an analysis of geological records from the Eemian Period  (129,000 to 116,000 years ago), showcasing examples of climate effects that could be expected in a world that is hotter and drier.

University of Queensland (UQ) Professor Hamish McGowan told UQ News the research shows that mega-drought events have been present in south-east Australia during similar climatic warming. 

“We found that, in the past, a similar amount of warming has been associated with mega-drought conditions all over south eastern Australia,” McGowan said.

“These drier conditions prevailed for centuries, sometimes for more than 1000 years, with El Niño events most likely increasing their severity.”

Engaging in paleoclimatology — the study of past climates — the research team aimed to assess what the effects of global warming would look like over the next 20 to 50 years, McGowan said, but that global warming is now occurring for different reasons.

“The Eemian Period is the most recent in Earth’s history when global temperatures were similar, or possibly slightly warmer than present,” he said.

“The ‘warmth’ of that period was in response to orbital forcing, the effect on climate of slow changes in the tilt of the Earth's axis and shape of the Earth's orbit around the sun.

“In modern times, heating is being caused by high concentrations of greenhouse gases, though this period is still a good analogue for our current-to-near-future climate predictions.”

A warmer, drier future

The research project was supported by Snowy Hydro Ltd, aiming to develop a more comprehensive understanding of likely climate variability as a result of global warming and the potential impact on the hydroclimate of southeast Australia.

Working alongside New South Wales Parks and Wildlife service, UQ researchers located and sampled stalagmites in the Yarrangobilly Caves from the Kosciuszko National Park.

Samples of calcium carbonate powder contained were collected from the stalagmites for analysis, which revealed periods of significantly reduced precipitation during the Eemian Period.

“They’re alarming findings, in a long list of alarming findings that climate scientists have released over the last few decades,” McGowan said.

“We hope that this new research allows for new insights to our future climate and the risks it may bring, such as drought and associated bushfires.

“But, importantly, if humans continue to warm the planet, this is the future we may all be looking at.”