Possible impacts of pollution aerosols on Australian climate and weather: A short review

This review considers possible impacts of pollution aerosols on Australian climate and weather. The main focus is on recent analyses of 20th Century simulations with a lowresolution version of the CSIRO global climate model. Two ensembles of simulations were performed, with and without anthropogenicaerosol forcing, in order to determine the impact of aerosols. These simulations suggest large effects on tropical Australian rainfall due to anthropogenic aerosol forcing from the Northern Hemisphere. In particular, the observed rainfall increase in northwestern Australia in recent decades may be attributable to the large Asian aerosol haze. The haze cools Asia and the surrounding oceans, thus altering the temperature gradient between Asian and Australia, and this affects the monsoonal winds and rainfall. Other impacts of anthropogenic aerosol forcing in the model include an improved simulation of temperature in the Indian Ocean, and a tendency for aerosols to make the sea-surface temperature pattern in the Pacific become more La Nina-like with time. These results suggest that more research into aerosols and their forcing of climate may be crucial to improving our understanding of climate change in Australia, and the broader Indo-Pacific region. Other studies, which have considered the possibility of climatic or meteorological effects due to Australian-sourced aerosol, are also briefly reviewed. Areas of interest are (a) recent data suggesting a substantial radiative forcing due to aerosol from biomass burning in northern Australia during the dry season, (b) an assertion, which remains contentious, that local aerosol pollution can significantly suppress rain formation in Australia, and (c) evidence from the 2003 Canberra bushfire that the dense smoke layer stabilised the lower atmosphere in the days after the fire, and prevented strong north-westerly winds from penetrating to the surface. The latter study suggests that inclusion of smoke aerosol in weather-prediction models could substantially improve critical weather forecasts during bushfires.