The impact that human-generated and natural atmospheric particles (aerosols) could be having on Australia's climate will be discussed next week in Canberra at a workshop involving some of the world's leading experts in the area.
CSIRO Marine and Atmospheric Research scientist, Dr Leon Rotstayn, says the influence aerosols have on climate is still one of the 'great unknowns' in climate science.
'We recently identified that the extensive pollution haze emanating from Asia may be re-shaping rainfall patterns and monsoonal winds in northern Australia. Establishing the impacts of aerosols across the rest of the country presents a new research challenge,' Dr Rotstayn says.
He was speaking on the eve of 'Something in the Air,' an international workshop organised by CSIRO and the Bureau of Meteorology through the Australian Climate Change Science Program and that has attracted 60 participants. At the centre of workshop discussions on August 18 and 19 will be a just-published review in the International Journal of Climatology of how aerosols could be influencing climate in Australia.
Sources of human-generated aerosols include; smoke-stack emissions, vehicle emissions and vegetation burning. Natural aerosol sources include; volcanic eruptions, dust storms and ocean plankton.
Dr Rotstayn says recent research suggests that the influence of aerosols on recent climate trends in the Southern Hemisphere has been comparable to greenhouse gases. 'Evidence of this is found in recent CSIRO climate modelling, which shows that the Asian aerosol haze affects temperature gradients between Asia and Australia, and may have caused an increase in rainfall over north-western Australia,' he says.
'Global ocean circulation provides another mechanism whereby aerosol changes in the Northern Hemisphere can affect climate in the Southern Hemisphere, suggesting an urgent need for further targeted studies using coupled ocean-atmosphere global climate models.
'In recent weeks, we had our first indication from CSIRO's climate model that Australian-sourced aerosols actively influence Australian climate and rainfall. Our latest simulations are much better at capturing natural rainfall variability over eastern Australia associated with the El Nino - La Nina cycle. Feedbacks due to Australian dust levels, which vary in tune with the natural El Nino cycle, appear to have improved the simulation of rainfall variability.
'To better model climate variability and climate change in the Australian region, more research is needed into aerosol sources, their atmospheric distributions, and how to incorporate these processes robustly in global climate models,' Dr Rotstayn said.