CSIRO, November 2008
- A Methodology for Determining the Impact of Climate Change on Ozone Levels in an Urban Area (Full report PDF - 11,526 KB) | (RTF - 24,248 KB)
- A Methodology for Determining the Impact of Climate Change on Ozone Levels in an Urban Area (Cover - Glossary PDF - 233 KB)
- A Methodology for Determining the Impact of Climate Change on Ozone Levels in an Urban Area (Introduction - Chapter 4 PDF - 513 KB)
- A Methodology for Determining the Impact of Climate Change on Ozone Levels in an Urban Area (Chapter 5 PDF - 1,459 KB)
- A Methodology for Determining the Impact of Climate Change on Ozone Levels in an Urban Area (Chapter 6 - Chapter 10 PDF - 769 KB)
The primary objective of this project was to demonstrate a methodology that can robustly predict ozone concentrations under climate change conditions for any period or location in Australia, and specifically to give an insight into the impact of climate change on ozone levels in Sydney in 20 and 50 years time. The methodology comprises a dynamical downscaling system that uses 200 km resolution global climate simulations and, through a two stage process, generates 3 km resolution mesoscale meteorological and trace gas concentration fields over populated areas.
The system was assessed for Sydney and was found to perform well in the prediction of the historical ozone climatology, mesoscale meteorology and peak ozone concentrations. Projected changes in Sydney weather and peak ozone concentrations were calculated for a global climatology based on an A2 SRES greenhouse gas emission scenario (a high end CO2 emissions growth scenario) and for a range of Sydney air pollution emission scenarios. When air pollution emissions were held fixed at current decade levels, it was found that the climate change scenario resulted in a 40% (2020-2030) and 200% (2050-2060) increase in the projected number of hospital admissions due to ozone pollution relative to 1996-2005. Analysis of the model results suggests that the increase in ozone-related morbidity resulted from an increase in daily maximum temperatures and the subsequent flow-on effects to factors which control ozone generation, such as the emissions of volatile organic compounds (which react to form ozone and are emitted at higher rates as temperatures increase), and increases in ozone precursor production rates (which also increase with ambient temperature).
The project also modelled the emissions reduction required to achieve compliance with AAQ-NEPM ozone standards in Sydney, for ozone generated under the 2051-2060 climatology. Ozone concentrations were predicted on the basis that emissions of carbon monoxide, volatile organic compounds and oxides of nitrogen (i.e. the precursors required for ozone generation) were progressively decreased by 40% and 60% compared to current decade emission rates. It was found that although the most stringent emission reductions lead to a 25 and 36% reduction in peak 1-hour and 4-hour ozone concentrations respectively, this was not sufficient to achieve compliance with the NEPM long term objectives for ozone.
The tools that were developed and assessed in this project are intended to provide a capability which can aid policy makers in formulating long term air pollution policies where the impact of climate change has to be considered. However, when applied for this purpose, it is recommended that the system be operated in an ensemble mode whereby a range of model projections are generated (based on different climate simulations and models) and an estimate of likelihood can be calculated.
It is further recommended that the system be enhanced to consider the formation and fate of fine particles (primary and secondary) as this air pollutant is considered to cause the largest air quality related health impacts in Australia.