It's not drought, it's climate change, say scientists

Melissa Fyfe in the Age (Australia): Scientists studying Victoria's crippling drought have, for the first time, proved the link between rising levels of greenhouse gases and the state's dramatic decline in rainfall. A three-year collaboration between the Bureau of Meteorology and CSIRO has confirmed what many scientists long suspected: that the 13-year drought is not just a natural dry stretch but a shift related to climate change.

Scientists working on the $7 million South Eastern Australian Climate Initiative say the rain has dropped away because the subtropical ridge - a band of high pressure systems that sits over the country's south - has strengthened over the past 13 years. These dry, high pressure systems have become stronger, bigger and more frequent and this intensification over the past century is closely linked to rising global temperatures, they found.

Climate data from across the past century shows the subtropical ridge has peaked and waned, often in line with rising global temperatures. But to see what role greenhouse gases played in the recent intensification, the scientists used sophisticated American computer climate models.

When they ran simulations with only the ''natural'' influences on temperature, such as changing levels of solar activity, they found there was no intensification of the subtropical ridge and no decline in rainfall.

But when they added human influences, such as greenhouse gases, aerosols and ozone depletion, the models mimicked what has occurred in south-east Australia - the high pressure systems strengthened, causing a significant drop in rainfall. ''It's reasonable to say that a lot of the current drought of the last 12 to 13 years is due to ongoing global warming,'' said the bureau's Bertrand Timbal…..

A dust storm in Wagga Wagga, Victoria, shot by Bidgee, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 3.0 License