The Big Dry In Australia's Southern States Is Caused By Greenhouse Gases And Will Get Worse: US Scientists

Getty/Ian Waldie

A government science agency in America has developed a high-resolution climate model which shows southern Australia’s long-term decline in fall and winter rainfall is caused by increases in manmade greenhouse gas emissions and ozone depletion.

The research by the NOAA (The National Oceanic and Atmospheric Administration), is published in the journal Nature Geoscience.

Tom Delworth, a research scientist at NOAA’s Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, says the model is a major step forward to improve the prediction of regional climate change, particularly involving water resources.

NOAA researchers conducted several climate simulations using this global climate model to study long-term changes in rainfall in various regions across the globe.

One of the most striking signals of change emerged over Australia, where a long-term decline in winter rainfall has been observed over parts of southern Australia.

Southern Australia’s decline in rainfall began around 1970 and has increased over the last four decades.

The model projects a continued decline in winter rainfall throughout the rest of the 21st century, with significant implications for regional water resources.

The drying is most severe over southwest Australia where the model forecasts a 40% decline in average rainfall by the late 21st century.

The above charts show the agreement between observed and model simulated rainfall changes supports the idea that human activity contributed to the drying of southwestern Australia and that the drying will increase in the 21st century. Changes in fall-winter rainfall from observations (top panel) as compared to model simulation of the past century (middle panel), and a model projection of the middle of the 21st century. Image: Graphic by NOAA’s Geophysical Fluid Dynamics Laboratory

Dr Nerilie Abram , from College of Physical and Mathematical Sciences at the Australian National University, says the research is a worrying picture for rainfall declines across southern parts of Australia, and particularly in southwest Western Australia.

Current research is converging upon a consensus view that increasing greenhouse gas levels as well as ozone depletion have shifted the climate belts southwards, causing southern parts of Australia to miss out on the winter rainfall which farmers rely on for their crops.

Dr Abram says this new study adds another compelling piece of evidence to idea that we can expect southern parts of Australia to keep getting drier over the coming century unless strong action can be taken to reduce greenhouse gas emissions.

“The impacts to Australia of the westerly winds pulling in tighter around Antarctica won’t just be seen in changes to our rainfall patterns,” Dr Abram says.

“These winds are also warming the oceans around the edges of Antarctica causing the margins of the large ice sheets to melt, and this is expected to have big implications for how quickly sea level will rise over the coming centuries.”

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