Australia: The Land Where Time Began

A biography of the Australian continent 

Australian regional rainfall decline has been attributed to anthropogenic greenhouse gases and ozone

Over the past few decades austral autumn and winter precipitation has declined in parts of southern and especially southwestern Australia (Nicholls, 2006; Timbal & Fawsett, 2013; Risbey, Pook & McIntosh, 2013; Hope, Timbal & Fawsett, 2010). At least part of this decline is associated with changes in large-scale atmospheric circulation, according to observations and climate models (Nicholls, 2006; Timbal & Fawsett, 2013; Cai & Cowan, 2006; Hendon, Thompson & Wheeler, 2007; Meneghini, Simmonds & Smith, 2007; Nicholls, 2009; Timbal, 2010; Timbal, Arblaster & Power, 2006; Cai, Cowan & Thatcher, 2012; Cai, Purich, Cowan van Rensch & Weller, 2014; Purich & Cowan, 2013; Cai, van Rensch, Borlace & Cowan, 2011). In this study the authors¹ used a high resolution global climate model to analyse the causes of this rainfall decline. The results of the these simulations show that many aspects of the regional rainfall decline that was observed in south and southwester Australia are reproduced  in response to anthropogenic changes in atmospheric greenhouse gases and ozone, though the anthropogenic aerosols did not contribute to the simulated decline in precipitation. It was also suggested by simulations of future climate that there would be an amplified drying in winter in most parts of southern Australia over the coming decades as a response to a high-end scenario of radiative forcing changes. Southwest Australia is the region where the simulation suggests the most pronounced drying would occur, with the total austral autumn reduction of precipitation of about 40 % by the late 21^st century.

Sources & Further reading

1. Delworth, T. L. and F. Zeng (2014). "Regional rainfall decline in Australia attributed to anthropogenic greenhouse gases and ozone levels." Nature Geosci 7(8): 583-587.