Global pollution may send Australia more rain
New Australian climate research suggests that tiny pollutant particles in the atmosphere which are believed to offset global warming, may also be changing global rainfall patterns.
The research, the first of its kind, by Dr Leon Rotstayn and colleagues from CSIRO Atmospheric Research is published in the international journal, Geophysical Research Letters.
"Climate model simulations show that the particles, known as aerosols, may be inducing a southward shift in tropical rainfall patterns, particularly over the Pacific Ocean," says Dr Rotstayn.
Aerosols are produced by both natural and human sources. The main human sources are the burning of fossil fuels and biomass.
"If this shift is confirmed, it will have an impact on the Australian and Asian monsoon," says Dr Rotstayn. "We may see some increase in rainfall over northern tropical Australia, with a decrease over most of the Indian sub-continent. There may also be a reduction in rainfall over China and South-East Asia"
Aerosols act as tiny nuclei on which cloud droplets can form. In regions where aerosol concentrations are high, such as polluted parts of the Northern Hemisphere, the additional cloud droplets make clouds brighter. As a result, more solar energy is reflected back into space, lowering the temperature in polluted areas. It is this cooling that Dr Rotstayn says be altering global rainfall patterns.
Dr Rotstayn's work relies on climate models which use complex, lengthy computer programs based upon the physical laws and equations of motion that govern the Earth's climate system. At this stage, the model has been limited to the impact of aerosols, however other factors are also expected to impact on rainfall.
Given this process is active over the Pacific Ocean, Dr Rotstayn suggests that El Niņo may be influenced, leading to further implications for Australia's rainfall. He says rainfall will also be impacted by the rise of aerosol emissions in parts of the developing world, and by global warming, which scientists believe will cause a shift towards more extreme rainfall events - bigger storms and more flash floods.
Future modelling will incorporate all of these factors.
CSIRO's research into aerosol and climate is in part supported by the Australian Greenhouse Office and involves collaboration with the University of Michigan in the USA.