Australia is a country dominated by desert. Much of the land, almost all of the interior, is best described as “parched.” And yet around the island's fringes is a verdant landscape home to nearly 24 million people.
Australians live near the coasts because that's where the water is—not just the ocean, but the rain. Or, that's where the rain has been. With climate change, even on the coasts water is now in short supply.
Since 1981 scientists have seen a strong drop in the amount of rainfall hitting parts of Australia, particularly in the southwest but also along the southern and eastern coasts. Most Australians live in the southeast, in cities like Sydney, Melbourne, Adelaide and Brisbane. But the hardest hit area has been the southwest, home to Perth, Australia's fourth largest city with nearly two million people. Perth is growing rapidly and is expected to push five million people by the middle of the century.
In a new study, climate scientists Thomas Delworth and Fanrong Zeng showed that the drying trend in southern Australia is caused in part by human-induced climate change. As we continue to pump greenhouses gases into the air, they say, southern Australia is only going to get drier.
The scientists used a number of climate models to try to recreate the patterns of wet and dry seen across Australia over the past three decades. Some of the models included anthropogenic warming—by way of rising greenhouse gases and ozone depletion—and some didn't.
When they tried to make sense of Australia's decline in winter precipitation without considering human-induced climate change, the numbers just wouldn't add up. The scientists say that they are particularly sure about the role of greenhouse gases and ozone in driving the drop in water in the southwest.
The research, says climate scientist David Karoly in Nature, “is one of the very few instances where regional rainfall changes have been linked to human-caused climate change.”
Running the clock forward, the researchers found that if we do little to combat further rise of atmospheric greenhouse gases, that rainfall in southwestern Australia could drop by 40 percent by the year 2100, compared to the period 1911-1970.