Trees alight in an intense bushfire.

Up close to an intense bushfire.

Climate change impacts on fire weather

A new study provides important new information about possible increased bushfire risk across south-east Australia, which may follow from climate change in coming decades.

  • 15 February 2006 | Updated 29 July 2013

The study, produced by CSIRO and the Bureau of Meteorology, will help communities across south-east Australia prepare for a possible increased bushfire risk.

Researchers assessed potential changes associated with climate change to these influences on fire-weather risk. The study, entitled Climate change impacts on fire-weather in south-east Australia, was completed by Kevin Hennessy from CSIRO and co-authors from the Bushfire Co-operative Research Centre (CRC) and the Australian Bureau of Meteorology.

Fire-weather risk relates to how a combination of weather variables influences the risk of a fire starting or its rate of spread, intensity, or difficulty to suppress. Fire risk is influenced by a number of factors including:

  • fuels
  • terrain
  • land management
  • suppression
  • weather. 

The study is based in south-east Australia, an area projected to become hotter and drier under climate change. In south-east Australia, since 1950:

  • rainfall has decreased
  • droughts have become more severe
  • the number of extremely hot days has risen.
The study is based in south-east Australia, an area projected to become hotter and drier under climate change.

Findings

The study found that the increase in fire-weather risk is generally largest inland. The combined frequencies of days with very high and extreme Forest Fire Danger Index ratings are likely to increase in south-east Australia by:

  • 4–25 per cent by 2020
  • 15–70 per cent by 2050.

The annual average of very high or extreme fire danger days in Canberra is likely to increase from the present 23.1 days to:

  • 25.6–28.6 days of very high or extreme fire danger by 2020
  • 27.9–38.3 days of very high or extreme fire danger by 2050. 

Some other key findings in the report are that:

  • Tasmania is likely to be relatively unaffected
  • The window for prescribed burning will narrow towards winter with higher fire-weather risk in spring, summer and autumn.

The study uses fire danger indices such as the Forest Fire Danger Index and the Grassland Fire Danger Index. They provide an indication of fire risk based on various combinations of weather variables including: 

  • daily temperature
  • rainfall
  • humidity
  • wind-speed.

These are calculated for historical weather records from 1974-2003 for sites in NSW, the ACT, Victoria and Tasmania.

Two climate change models are then used to generate climate change scenarios for 2020 and 2050, including changes in average climate and daily weather variability. The CSIRO climate models used for this report were developed with assistance from the Australian Greenhouse Office. Fire danger indices are then calculated for 2020 and 2050.

A key finding of this study is that an increase in fire-weather risk is likely at most sites in 2020 and 2050, including the average number of days when the Forest Fire Danger Risk rating is very high or extreme.

Uncertainties

There are several uncertainties when assessing potential changes to fire-weather risk associated with climate change:

  • the quality of data for some weather variables
  • the possibility of different results from use of other climate models
  • changes in seasonal indicators  used for fire preparedness planning
  • changes in rainfall thresholds required to control fires
  • changes in ignition and fuel load
  • changes in El Nino-Southern Oscillation events under climate change.

Publication details

Hennessy K, Lucas C, Nicholls N, Bathols J, Suppiah R, Ricketts J. 2006. Climate change impacts on fire-weather in south-east Australia. CSIRO, Australia. [PDF file, 2.3MB, 91 pages].

The study was funded by the Australian Federal Government and the State Governments of New South Wales, the Australian Capital Territory, Victoria and Tasmania.