Aerosols influence Australian weather


Climate change

Storm approaching

Credit: Wikimedia

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New research suggests that aerosols, fine particles or droplets suspended in the atmosphere, may have a greater impact on patterns of Australian rainfall and future climate change than previously thought.

"We have identified that the extensive pollution haze emanating from Asia may be re-shaping rainfall patterns in northern Australia, but we [also] wonder what impact natural and human-generated aerosols are having across the rest of the country," said Leon Rotstayn, an atmospheric scientist from Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Human activities that generate pollutant aerosols in large quantities include motor vehicle use, vegetation burning and industry pursuits, while natural sources range from volcanoes and dust storms to ocean plankton, which release sulfate particles into the air.

These aerosols actually exert a cooling effect on the climate, by reflecting solar radiation back into space before it can reach the Earth’s surface. Because of this, aerosols have been partly masking the warming effect of rising greenhouse gas levels.

But with aerosol pollution predicted to decrease over the coming decades, the unmasking of the greenhouse effect may lead to accelerated global warming, Rotstayn said, presenting at today’s International Conference on Southern Hemisphere Meteorology and Oceanography in Melbourne.

Adding to their influence on the planet, by altering the distribution of solar heating at the Earth’s surface, aerosols can also actively force changes in winds and ocean currents.

"Recent climate modelling at CSIRO shows that there may be important effects on Australian climate due to aerosol pollution from the Northern Hemisphere. These include an increase of rainfall in north-western Australia, and an increase of air pressure over southern Australia, which may have [already] contributed to less rainfall there," said Rotstayn.

Further research into how aerosols are influencing climate and rainfall patterns across Australia is critical to scientists’ ability to more accurately predict the longer-term effects of climate change, he added.

"It is crucial to quantify the relative roles of different drivers of recent Australian rainfall changes. A rainfall decline attributed to natural variability will be a passing phenomenon, and changes forced by human-generated aerosols are likely to be more short-term than changes forced by increasing greenhouse gases. The implications for decision makers will be very different, depending on whether the drivers are long-term or short-term."