When it rains, it pours! This old idea looks set to be Australia’s future

In the last few years, Australia has faced both flooding rains and some of the lowest rainfall on record. Now, researchers from the Chinese Academy of Sciences have the data that explains why rain in Australia has seemed so unpredictable.

The researchers have shown that human-induced climate warming is driving increases in rainfall variability over 75% of the Earth’s land, and they say the effects are especially prominent in Australia.

The study looked at increases in rainfall variability, which can mean wetter wet periods and drier dry periods. They found that daily variability has increased by 1.2% per decade globally, and that humans are largely to blame.

“The increase in rainfall variability is mainly due to anthropogenic greenhouse gas emissions, which have led to a warmer and more humid atmosphere,” said Dr Zhang Wenxia, lead author of the study. 

“This means that even if the atmospheric circulation remains the same, the additional moisture in the air leads to more intense rain events and more drastic fluctuations between them.”

Professor Steven Sherwood at the UNSW Climate Change Research Centre, who was not involved in the study, told the AusSMC that this means rainier rainy periods and drier dry periods. 

“This is going to increase as global warming continues, enhancing the chances of droughts and/or floods.”

The paper identified Australia as being a particular hotspot for rainfall variability. Dr Milton Speer from the University of Technology Sydney said the paper’s findings are significant, and that other recent studies have had similar conclusions. 

“In fact, for a large part of southeast Australia, increasing variability is precisely what has happened in relation to precipitation as global warming increases,” he said.

But Dr Tom Beer, an environmental risk expert and former Program Leader of CSIRO Climate Change and Variability, was critical of the claim that Australia was especially impacted. 

“The authors have the good grace to ‘note that the signal is weak over Australia for the shorter period of 1950-2020 because of large internal variability’,” he said. 

As to what all this variability means for the future, the research author Dr Zhou Tianjun warned that “the future we worried about is already here.” 

“The increased variability in precipitation we observed adds crucial evidence of larger daily changes, making it more difficult to predict and prepare for environmental impacts.”

You can read the full AusSMC Expert Reaction here.

This article originally appeared in Science Deadline, a weekly newsletter from the Australian Science Media Centre (AusSMC).