Australia — Scientists believe more bushfires generated by rising temperatures and lower rainfall will lead to lower air quality over a greater number of days in Australia, particularly in the south-east.
In a presentation to the GREENHOUSE 2009 conference in Perth today, CSIROs Dr Mick Meyer said measurements taken at the Bayside Air Quality Station in Melbournes south-east during the 2003 and 2006 bushfires provided a guide to what could be experienced as the climate changes.
While air quality standards generally appear to be improving, a future issue will be quality during times of wildfire for which there is little control and during autumn and winter prescribed burning when there is more control, Dr Meyer said.
Dr Meyer, from the Centre for Australian Weather and Climate Research, said the 2003 bushfires burnt an area of 1.1 million hectares and the 2006 fires 1.3 million hectares. This compares with approximately 450,000 hectares burnt during the February 2009 fires in Victoria.
From December 2006 to February 2007 bushfires in the Great Divide burned for 69 days. On several occasions, thick smoke haze was transported to the Melbourne CBD and particulate matter concentrations at several Environmental Protection Agency Victoria air quality monitoring sites peaked at four times the National Environment Protection Measure 24-hour standard.
Analysis of the measurements showed:
High concentrations of fine particles between 0.1 and 0.5 µm, diameter, largely composed of non-volatile organic material. Particles of this size are easily respired and can cause significant health impacts.
High concentrations of carbon monoxide and nitrogen dioxide.
Elevated concentrations of ozone.
The fingerprint is distinctly different from industrial and vehicular pollution sources.
Dr Meyer said that under a changing climate the frequency of bushfires, the duration of the bushfire season and the severity of bushfires are expected to change. Current projections for south-eastern Australia suggest an increase in the frequency of very high and extreme fire days and that periods suitable for prescribed burning would move towards winter.
In addition to the health impacts of increased fire intensity, duration and frequency, biomass burning also results in the emission of significant quantities of trace gases and aerosols to the atmosphere, and these subsequently can influence cloud processes.
They also reduce visibility, influence atmospheric photochemistry and can be inhaled into the deepest parts of the lungs impacting on human health, Dr Meyer said
Savanna forest burning in northern Australia accounts for the majority of carbon emissions from burning, and 90-95 per cent of this is from wildfires. These savannah fires contribute about eight per cent of global carbon emissions from vegetation fires.