The new NOAA figures also place the blame fully on human causes.
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One could argue that, after some four decades of progressive drying, southern Australia no longer has a drought. After all, would anyone argue that Death Valley, with its yearly inch or so of rain, is suffering through a drought? No, it's just a dry place. This is the situation much of the Sunburnt Country finds itself in after consistent, prolonged rainfall declines beginning in 1970. It's just dry; that's the state of things.
A new NOAA study, published in the journal Nature Geoscience, applies a recently developed global climate model to the Australian situation, evaluating both the likely causes of the chronic dryness and the likely future of the region's climate. By simulating climate change scenarios involving both manmade and natural causes, the research team was able to mostly eliminate non-anthropogenic causes, like volcano eruptions and changes in the Sun's radiation. With these gone, the precipitation changes fell squarely on human-caused increases in greenhouse gases and continued ozone thinning.
"In our simulations, many aspects of the observed regional rainfall decline over southern and southwest Australia are reproduced in response to anthropogenic changes in levels of greenhouse gases and ozone in the atmosphere," the study summarizes, "whereas anthropogenic aerosols do not contribute to the simulated precipitation decline." More specifically, large-scale climate drivers include, "poleward movement of the westerly winds and increasing atmospheric surface pressure over parts of southern Australia."
As for the future, it doesn't get better. "Simulations of future climate with this model suggest amplified winter drying over most parts of southern Australia in the coming decades in response to a high-end scenario of changes in radiative forcing," the NOAA team says. "The drying is most pronounced over southwest Australia, with total reductions in austral autumn and winter precipitation of approximately 40 perent by the late twenty-first century."
Of course, southern Australia isn't the only locale experiencing long-term water-related devastation. "Predicting potential future changes in water resources, including drought, are an immense societal challenge," said co-author Tom Delworth in a statement from the agency. "This new climate model will help us more accurately and quickly provide resource planners with environmental intelligence at the regional level. The study of Australian drought helps to validate this new model, and thus builds confidence in this model for ongoing studies of North American drought."
It's hard not to think of Toowoomba, the mid-sized Queensland city that famously rejected a cheap wastewater recycling program in favor of a vastly more expensive pipeline connecting it to a distant supply, largely thanks to bogus threats of contamination and sickness. In a 2011 news article recalling the controversial vote/plan, Rosemary Morley, one of the grassroots organizers against the proposal, quipped, “We never needed it. We still don't need it and quite frankly I'm dumbstruck so many people said it would never rain again.” For at least some large portion of Toowoomba's population, however, a rainfall decline of nearly 50 percent means exactly that.